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Sutter E, Ghimire P, Sutter P. Directing Charge Carriers and Ferroelectric Domains at Lateral Interfaces in van der Waals Heterostructures. ACS NANO 2024. [PMID: 39439076 DOI: 10.1021/acsnano.4c11341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2024]
Abstract
Emergent phenomena in traditional ferroelectrics are frequently observed at heterointerfaces. Accessing such functionalities in van der Waals ferroelectrics requires the formation of layered heterostructures, either vertically stacked (similar to oxide ferroelectrics) or laterally stitched (without equivalent in 3D-crystals). Here, we investigate lateral heterostructures of the ferroelectric van der Waals semiconductors SnSe and SnS. A two-step process produces ultrathin crystals comprising an SnSe core laterally joined to an SnS edge-band, as confirmed by Raman spectroscopy, transmission electron microscopy (TEM) imaging, and electron diffraction. TEM shows a moiré pattern across the SnSe core due to coverage by an ultrathin SnS layer. The ability of the lateral interface (IF) to direct excited carriers, probed by cathodoluminescence, shows electron transfer over 560 nm diffusion length from the SnS edge-band. Large, thin flakes supporting ferroelectricity allow investigating domains and domain wall interactions in uniform crystals and lateral heterostructures. Polarized optical microscopy of sub-20 nm flakes consistently shows ⟨110⟩ oriented stripe domains with mirror-twin domain walls. Heterostructures adopt two domain configurations, with domains either constrained to the SnSe core or propagating across the entire SnSe-SnS flakes. The combined results demonstrate multifunctional van der Waals heterostructures with high-quality IFs presenting extraordinary opportunities for manipulating carrier flows and ferroelectric domain patterns.
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Affiliation(s)
- Eli Sutter
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Pramod Ghimire
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Peter Sutter
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
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2
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Duranti C, Bagni G, Iorio J, Colasurdo R, Devescovi V, Arcangeli A. Effects of Germanium embedded fabric on the chondrogenic differentiation of adipose derived stem cells. Tissue Cell 2024; 90:102507. [PMID: 39128191 DOI: 10.1016/j.tice.2024.102507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Revised: 07/12/2024] [Accepted: 07/29/2024] [Indexed: 08/13/2024]
Abstract
Osteoarthritis (OA) is a clinical state which is identified by the degeneration of articular cartilage. OA is a common condition (>500 millions of people affected worldwide), whose frequency is anticipated to continue to rise (> 110 % increase worldwide since 2019). The treatment for early-stage OA is based on a combination of therapeutic approaches, which can include regenerative medicine based on Adipose Derived Stem Cells (ADSCs). Germanium embedded Incrediwear® functional Cred40 fabric has been shown to have positive effects on OA clinically and is envisaged to give encouraging effects also on tissue regeneration. Still, the biological mechanisms underlying this therapeutic modality have not yet been fully defined. We tested the hypothesis that Germanium-embedded Incrediwear® functional Cred40 fabric could enhance chondrogenic differentiation. To this purpose, we applied Incrediwear® to human adipose-derived stem cells (hADSCs) induced to chondrogenic differentiation in vitro. Chondrogenic markers (ACAN, SOX9, RUNX2, COL2A1, COL10A1) were quantified following 21 days of treatment. We also assessed extracellular matrix (ECM) deposition (specifically Collagen and glycosaminoglycans (GAGs)) using Alcian Blue and Sirius Red staining. Here, we provide pilot data to demonstrate that Germanium-embedded Incrediwear® functional Cred40 fabric can enhance hADSCs chondrogenic differentiation and maturity and potentially induce events of cartilage regeneration.
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Affiliation(s)
- Claudia Duranti
- Department of Experimental and Clinical Medicine, University of Florence, Viale GB Morgagni 50, Firenze 50134, Italy; MCK Therapeutics Srl, Via Ciliegiole 98, Pistoia, Italy
| | - Giacomo Bagni
- Department of Experimental and Clinical Medicine, University of Florence, Viale GB Morgagni 50, Firenze 50134, Italy
| | - Jessica Iorio
- Department of Experimental and Clinical Medicine, University of Florence, Viale GB Morgagni 50, Firenze 50134, Italy
| | - Rossella Colasurdo
- Department of Experimental and Clinical Medicine, University of Florence, Viale GB Morgagni 50, Firenze 50134, Italy
| | - Valentina Devescovi
- Department of Experimental and Clinical Medicine, University of Florence, Viale GB Morgagni 50, Firenze 50134, Italy
| | - Annarosa Arcangeli
- Department of Experimental and Clinical Medicine, University of Florence, Viale GB Morgagni 50, Firenze 50134, Italy; MCK Therapeutics Srl, Via Ciliegiole 98, Pistoia, Italy.
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Sutter E, Komsa HP, Sutter P. Valley-selective carrier transfer in SnS-based van der Waals heterostructures. NANOSCALE HORIZONS 2024. [PMID: 39171396 DOI: 10.1039/d4nh00231h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/23/2024]
Abstract
Valleytronics, i.e., use of the valley degree of freedom in semiconductors as an information carrier, is a promising alternative to conventional approaches for information processing. Transition metal dichalcogenides with degenerate K/K' valleys have received attention as prototype 2D/layered semiconductors for valleytronics, but these systems rely on exotic effects such as the valley-Hall effect for electrical readout of the valley occupancy. Non-traditional valleytronic systems hosting sets of addressable non-degenerate valleys could overcome this limitation. In the van der Waals semiconductor Sn(II) sulfide (SnS), for instance, different bandgaps and band edges may allow manipulating the population of the X- and Y-valleys via charge transfer across interfaces to other layered semiconductors. Here, we establish this concept by comparing SnS flakes and SnS-based heterostructures. Cathodoluminescence spectroscopy shows a striking reversal of the luminescence intensity of the two valleys in SnS-GeS van der Waals stacks, which stems from a selective electron transfer from the Y-valley into GeS while X-valley electrons remain confined to SnS. Our results suggest that non-traditional systems, embodied here by SnS-based van der Waals heterostructures, open avenues for valley-selective readout relying on design parameters such as heterostructure band offsets that are among the core concepts of semiconductor technology.
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Affiliation(s)
- E Sutter
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
| | - H-P Komsa
- Microelectronics Research Unit, University of Oulu, FI-90014 Oulu, Finland
| | - P Sutter
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
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Khanmohammadi S, Kushnir Friedman K, Chen E, Kastuar SM, Ekuma CE, Koski KJ, Titova LV. Tailoring Ultrafast Near-Band Gap Photoconductive Response in GeS by Zero-Valent Cu Intercalation. ACS APPLIED MATERIALS & INTERFACES 2024; 16:16445-16452. [PMID: 38528798 DOI: 10.1021/acsami.3c19251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/27/2024]
Abstract
Zero-valent intercalation of atomic metals into the van der Waals gap of layered materials can be used to tune their electronic, optical, thermal, and mechanical properties. Here, we report the impact of intercalating ∼3 atm percent of zero-valent copper into germanium sulfide (GeS). Advanced many-body calculations predict that copper introduces quasi-localized intermediate band states, and time-resolved THz spectroscopy studies demonstrate that those states have prominent effects on the photoconductivity of GeS. Cu-intercalated GeS exhibits a faster rise of transient photoconductivity and a shorter lifetime of optically injected carriers following near-gap excitation with 800 nm pulses. At the same time, Cu intercalation improves free carrier mobility from 1100 to 1300 cm2 V-1 s-1, which we attribute to the damping of acoustic phonons observed in Brillouin scattering and consequent reduction of phonon scattering.
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Affiliation(s)
- Sepideh Khanmohammadi
- Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, United States
| | - Kateryna Kushnir Friedman
- Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, United States
| | - Ethan Chen
- Department of Chemistry, University of California Davis, Davis, California 95616, United States
| | - Srihari M Kastuar
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Chinedu E Ekuma
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Kristie J Koski
- Department of Chemistry, University of California Davis, Davis, California 95616, United States
| | - Lyubov V Titova
- Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, United States
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Barreto RR, Ribeiro TC, Soares GHR, Pereira E, Miquita DR, Safar GAM, Mazzoni MSC, Malachias A, Magalhaes-Paniago R. Evidence of thickness-dependent surface-induced ferroelectricity in few-layer germanium sulfide obtained via scanning tunneling spectroscopy. NANOSCALE 2024. [PMID: 38426356 DOI: 10.1039/d3nr05566c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/02/2024]
Abstract
The discovery of ferroelectricity in two-dimensional van der Waals materials has sparked enormous interest from the scientific community, due to its possible applications in next-generation nanoelectronic devices, such as random-access memory devices, digital signal processors, and solar cells, among others. In the present study, we used vapor phase deposition to synthesize ultrathin germanium sulfide nano-flakes on a highly oriented pyrolytic graphite substrate. Nanostructures of variable thicknesses were characterized using scanning tunneling microscopy and spectroscopy. Tunneling currents under forward and backward biases were measured as a function of nano-flake thickness. Remarkably, we clearly observed a hysteresis pattern, which we attributed to surface ferroelectric behavior, consistent with the screening conditions of polarization charges. The effect increases as the number of layers is reduced. This experimental result may be directly applicable to miniaturized memory devices, given the two-dimensional nature of this effect.
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Affiliation(s)
- Rafael R Barreto
- Physics Department, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil.
| | - Thiago C Ribeiro
- Physics Department, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil.
| | - Gustavo H R Soares
- Physics Department, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil.
| | - Everton Pereira
- Physics Department, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil.
| | - Douglas R Miquita
- Microscopic Center, Federal University of Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil
| | - Gustavo A M Safar
- Physics Department, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil.
| | - Mario S C Mazzoni
- Physics Department, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil.
| | - Angelo Malachias
- Physics Department, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil.
| | - Rogerio Magalhaes-Paniago
- Physics Department, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil.
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Ribeiro TC, Fonseca DHS, Barreto RR, Pereira-Andrade E, Miquita DR, Malachias A, Magalhaes-Paniago R. Scanning Tunneling Spectroscopy Method for the Prediction of Semiconductor Heterojunction Performance as a Prequel for Device Development. ACS APPLIED MATERIALS & INTERFACES 2024; 16:1650-1658. [PMID: 38117664 DOI: 10.1021/acsami.3c11876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
The prediction of semiconductor device performance is a persistent challenge in materials science, and the ability to anticipate useful specifications prior to construction is crucial for enhancing the overall efficiency. In this study, we investigate the constituents of a solar cell by employing scanning tunneling microscopy (STM) and spectroscopy (STS). Through our observations, we identify a spatial distribution of the dopant type in thin films of materials that were designed to present major p-doping for germanium sulfide (GeS) and dominant n-doping for tin disulfide (SnS2). By generating separate STS maps for each semiconductor film and conducting a statistical analysis of the gap and doping distribution, we determine intrinsic limitations for the solar cell efficiency that must be understood prior to processing. Subsequently, we fabricate a solar cell utilizing these materials (GeS and SnS2) via vapor phase deposition and carry out a characterization using standard J-V curves under both dark/illuminated irradiance conditions. Our devices corroborate the expected reduced efficiency due to doping fluctuation but exhibit stable photocurrent responses. As originally planned, quantum efficiency measurements reveal that the peak efficiency of our solar cell coincides with the range where the standard silicon solar cells sharply decline. Our STS method is suggested as a prequel to device development in novel material junctions or deposition processes where fluctuations of doping levels are retrieved due to intrinsic material characteristics such as the occurrence of defects, roughness, local chemical segregation, and faceting or step bunching.
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Affiliation(s)
- Thiago C Ribeiro
- Departament of Physics, Federal University of Minas Gerais, Belo Horizonte, MG 30123-970, Brazil
| | - Daniel H S Fonseca
- Departament of Physics, Federal University of Minas Gerais, Belo Horizonte, MG 30123-970, Brazil
| | - Rafael Reis Barreto
- Departament of Physics, Federal University of Minas Gerais, Belo Horizonte, MG 30123-970, Brazil
| | - Everton Pereira-Andrade
- Departament of Physics, Federal University of Minas Gerais, Belo Horizonte, MG 30123-970, Brazil
| | - Douglas R Miquita
- Microscopy Center, Federal University of Minas Gerais, Belo Horizonte, MG 30123-970, Brazil
| | - Angelo Malachias
- Departament of Physics, Federal University of Minas Gerais, Belo Horizonte, MG 30123-970, Brazil
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Luo X, Sun J, Kong D, Lei Y, Gong F, Zhang T, Shen Z, Wang K, Luo H, Xu Y. The role of germanium in diseases: exploring its important biological effects. J Transl Med 2023; 21:795. [PMID: 37940963 PMCID: PMC10634018 DOI: 10.1186/s12967-023-04643-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 10/20/2023] [Indexed: 11/10/2023] Open
Abstract
With the development of organic germanium and nanotechnology, germanium serves multiple biological functions, and its potential value in biochemistry and medicine has increasingly captured the attention of researchers. In recent years, germanium has gradually gained significance as a material in the field of biomedicine and shows promising application prospects. However, there has been a limited amount of research conducted on the biological effects and mechanisms of germanium, and a systematic evaluation is still lacking. Therefore, the aim of this review is to systematically examine the application of germanium in the field of biomedicine and contribute new insights for future research on the functions and mechanisms of germanium in disease treatment. By conducting a comprehensive search on MEDLINE, EMBASE, and Web of Science databases, we systematically reviewed the relevant literature on the relationship between germanium and biomedicine. In this review, we will describe the biological activities of germanium in inflammation, immunity, and antioxidation. Furthermore, we will discuss its role in the treatment of neuroscience and oncology-related conditions. This comprehensive exploration of germanium provides a valuable foundation for the future application of this element in disease intervention, diagnosis, and prevention.
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Affiliation(s)
- Xiao Luo
- Yunnan Technological Innovation Centre of Drug Addiction Medicine, Yunnan University, Kunming, 650032, China
- Department of Gastrointestinal and Hernia Surgery, First Affiliated Hospital of Kunming Medical University, Kunming, 650032, China
| | - Jiaxue Sun
- Yunnan Technological Innovation Centre of Drug Addiction Medicine, Yunnan University, Kunming, 650032, China
- Department of Gastrointestinal and Hernia Surgery, First Affiliated Hospital of Kunming Medical University, Kunming, 650032, China
| | - Deshenyue Kong
- Yunnan Technological Innovation Centre of Drug Addiction Medicine, Yunnan University, Kunming, 650032, China
- Department of Gastrointestinal and Hernia Surgery, First Affiliated Hospital of Kunming Medical University, Kunming, 650032, China
| | - Yi Lei
- Department of Gastrointestinal and Hernia Surgery, First Affiliated Hospital of Kunming Medical University, Kunming, 650032, China
| | - Fangyou Gong
- Department of Gastrointestinal and Hernia Surgery, First Affiliated Hospital of Kunming Medical University, Kunming, 650032, China
| | - Tong Zhang
- Department of Gastrointestinal and Hernia Surgery, First Affiliated Hospital of Kunming Medical University, Kunming, 650032, China
| | - Zongwen Shen
- Department of Gastrointestinal and Hernia Surgery, First Affiliated Hospital of Kunming Medical University, Kunming, 650032, China
| | - Kunhua Wang
- Yunnan Technological Innovation Centre of Drug Addiction Medicine, Yunnan University, Kunming, 650032, China.
- Yunnan University, Kunming, 650032, China.
| | - Huayou Luo
- Department of Gastrointestinal and Hernia Surgery, First Affiliated Hospital of Kunming Medical University, Kunming, 650032, China.
| | - Yu Xu
- Yunnan Technological Innovation Centre of Drug Addiction Medicine, Yunnan University, Kunming, 650032, China.
- Department of Gastrointestinal and Hernia Surgery, First Affiliated Hospital of Kunming Medical University, Kunming, 650032, China.
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Hlushchenko D, Siudzinska A, Cybinska J, Guzik M, Bachmatiuk A, Kudrawiec R. Stability of mechanically exfoliated layered monochalcogenides under ambient conditions. Sci Rep 2023; 13:19114. [PMID: 37925524 PMCID: PMC10625602 DOI: 10.1038/s41598-023-46092-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 10/27/2023] [Indexed: 11/06/2023] Open
Abstract
Monochalcogenides of groups III (GaS, GaSe) and VI (GeS, GeSe, SnS, and SnSe) are materials with interesting thickness-dependent characteristics, which have been applied in many areas. However, the stability of layered monochalcogenides (LMs) is a real problem in semiconductor devices that contain these materials. Therefore, it is an important issue that needs to be explored. This article presents a comprehensive study of the degradation mechanism in mechanically exfoliated monochalcogenides in ambient conditions using Raman and photoluminescence spectroscopy supported by structural methods. A higher stability (up to three weeks) was observed for GaS. The most reactive were Se-containing monochalcogenides. Surface protrusions appeared after the ambient exposure of GeSe was detected by scanning electron microscopy. In addition, the degradation of GeS and GeSe flakes was observed in the operando experiment in transmission electron microscopy. Additionally, the amorphization of the material progressed from the flake edges. The reported results and conclusions on the degradation of LMs are useful to understand surface oxidation, air stability, and to fabricate stable devices with monochalcogenides. The results indicate that LMs are more challenging for exfoliation and optical studies than transition metal dichalcogenides such as MoS2, MoSe2, WS2, or WSe2.
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Affiliation(s)
- Daria Hlushchenko
- Lukasiewicz Research Network, PORT Polish Center for Technology Development, Stablowicka 147, 54-066, Wroclaw, Poland.
- Department of Semiconductor Materials Engineering, Faculty of Fundamental Problems of Science and Technology, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370, Wroclaw, Poland.
| | - Anna Siudzinska
- Lukasiewicz Research Network, PORT Polish Center for Technology Development, Stablowicka 147, 54-066, Wroclaw, Poland
| | - Joanna Cybinska
- Lukasiewicz Research Network, PORT Polish Center for Technology Development, Stablowicka 147, 54-066, Wroclaw, Poland
- Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie 14, 50-383, Wroclaw, Poland
| | - Malgorzata Guzik
- Lukasiewicz Research Network, PORT Polish Center for Technology Development, Stablowicka 147, 54-066, Wroclaw, Poland
- Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie 14, 50-383, Wroclaw, Poland
| | - Alicja Bachmatiuk
- Lukasiewicz Research Network, PORT Polish Center for Technology Development, Stablowicka 147, 54-066, Wroclaw, Poland
| | - Robert Kudrawiec
- Lukasiewicz Research Network, PORT Polish Center for Technology Development, Stablowicka 147, 54-066, Wroclaw, Poland.
- Department of Semiconductor Materials Engineering, Faculty of Fundamental Problems of Science and Technology, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370, Wroclaw, Poland.
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Sutter E, Sutter P. Self-Assembly of Mixed-Dimensional GeS 1- x Se x (1D Nanowire)-(2D Plate) Van der Waals Heterostructures. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2302592. [PMID: 37312407 DOI: 10.1002/smll.202302592] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 05/09/2023] [Indexed: 06/15/2023]
Abstract
The integration of dissimilar materials into heterostructures is a mainstay of modern materials science and technology. An alternative strategy of joining components with different electronic structure involves mixed-dimensional heterostructures, that is, architectures consisting of elements with different dimensionality, for example, 1D nanowires and 2D plates. Combining the two approaches can result in hybrid architectures in which both the dimensionality and composition vary between the components, potentially offering even larger contrast between their electronic structures. To date, realizing such heteromaterials mixed-dimensional heterostructures has required sequential multi-step growth processes. Here, it is shown that differences in precursor incorporation rates between vapor-liquid-solid growth of 1D nanowires and direct vapor-solid growth of 2D plates attached to the wires can be harnessed to synthesize heteromaterials mixed-dimensional heterostructures in a single-step growth process. Exposure to mixed GeS and GeSe vapors produces GeS1- x Sex van der Waals nanowires whose S:Se ratio is considerably larger than that of attached layered plates. Cathodoluminescence spectroscopy on single heterostructures confirms that the bandgap contrast between the components is determined by both composition and carrier confinement. These results demonstrate an avenue toward complex heteroarchitectures using single-step synthesis processes.
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Affiliation(s)
- Eli Sutter
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Peter Sutter
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
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Mohammadzadeh MR, Hasani A, Jaferzadeh K, Fawzy M, De Silva T, Abnavi A, Ahmadi R, Ghanbari H, Askar A, Kabir F, Rajapakse R, Adachi MM. Unique Photoactivated Time-Resolved Response in 2D GeS for Selective Detection of Volatile Organic Compounds. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2205458. [PMID: 36658730 PMCID: PMC10074048 DOI: 10.1002/advs.202205458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 12/19/2022] [Indexed: 06/17/2023]
Abstract
Volatile organic compounds (VOCs) sensors have a broad range of applications including healthcare, process control, and air quality analysis. There are a variety of techniques for detecting VOCs such as optical, acoustic, electrochemical, and chemiresistive sensors. However, existing commercial VOC detectors have drawbacks such as high cost, large size, or lack of selectivity. Herein, a new sensing mechanism is demonstrated based on surface interactions between VOC and UV-excited 2D germanium sulfide (GeS), which provides an effective solution to distinguish VOCs. The GeS sensor shows a unique time-resolved electrical response to different VOC species, facilitating identification and qualitative measurement of VOCs. Moreover, machine learning is utilized to distinguish VOC species from their dynamic response via visualization with high accuracy. The proposed approach demonstrates the potential of 2D GeS as a promising candidate for selective miniature VOCs sensors in critical applications such as non-invasive diagnosis of diseases and health monitoring.
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Affiliation(s)
| | - Amirhossein Hasani
- School of Engineering ScienceSimon Fraser UniversityBurnabyBritish ColumbiaV5A 1S6Canada
| | - Keyvan Jaferzadeh
- Department of Computer Science and Software EngineeringConcordia UniversityMontrealQuebecH3G 1M8Canada
| | - Mirette Fawzy
- Department of PhysicsSimon Fraser UniversityBurnabyBritish ColumbiaV5A 1S6Canada
| | - Thushani De Silva
- School of Engineering ScienceSimon Fraser UniversityBurnabyBritish ColumbiaV5A 1S6Canada
| | - Amin Abnavi
- School of Engineering ScienceSimon Fraser UniversityBurnabyBritish ColumbiaV5A 1S6Canada
| | - Ribwar Ahmadi
- School of Engineering ScienceSimon Fraser UniversityBurnabyBritish ColumbiaV5A 1S6Canada
| | - Hamidreza Ghanbari
- School of Engineering ScienceSimon Fraser UniversityBurnabyBritish ColumbiaV5A 1S6Canada
| | - Abdelrahman Askar
- School of Engineering ScienceSimon Fraser UniversityBurnabyBritish ColumbiaV5A 1S6Canada
| | - Fahmid Kabir
- School of Engineering ScienceSimon Fraser UniversityBurnabyBritish ColumbiaV5A 1S6Canada
| | - R.K.N.D. Rajapakse
- School of Engineering ScienceSimon Fraser UniversityBurnabyBritish ColumbiaV5A 1S6Canada
| | - Michael M. Adachi
- School of Engineering ScienceSimon Fraser UniversityBurnabyBritish ColumbiaV5A 1S6Canada
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11
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Sutter E, Komsa HP, Puretzky AA, Unocic RR, Sutter P. Stacking Fault Induced Symmetry Breaking in van der Waals Nanowires. ACS NANO 2022; 16:21199-21207. [PMID: 36413759 DOI: 10.1021/acsnano.2c09172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
While traditional ferroelectrics are based on polar crystals in bulk or thin film form, two-dimensional and layered materials can support mechanisms for symmetry breaking between centrosymmetric building blocks, e.g., by creating low-symmetry interfaces in van der Waals stacks. Here, we introduce an approach toward symmetry breaking in van der Waals crystals that relies on the spontaneous incorporation of stacking faults in a nonpolar bulk layer sequence. The concept is realized in nanowires consisting of Se-rich group IV monochalcogenide (GeSe1-xSx) alloys, obtained by vapor-liquid-solid growth. The single crystalline wires adopt a layered structure in which the nonpolar A-B bulk stacking along the nanowire axis is interrupted by single-layer stacking faults with local A-A' stacking. Density functional theory explains this behavior by a reduced stacking fault formation energy in GeSe (or Se-rich GeSe1-xSx alloys). Computations demonstrate that, similar to monochalcogenide monolayers, the inserted A-layers should show a spontaneous electric polarization with a switching barrier consistent with a Curie temperature above room temperature. Second-harmonic generation signals are consistent with a variable density of stacking faults along the wires. Our results point to possible routes for designing ferroelectrics via the layer stacking in van der Waals crystals.
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Affiliation(s)
- Eli Sutter
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska68588, United States
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska68588, United States
| | - Hannu-Pekka Komsa
- Faculty of Information Technology and Electrical Engineering, University of Oulu, FI-90014, Oulu, Finland
| | - Alexander A Puretzky
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37830, United States
| | - Raymond R Unocic
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37830, United States
| | - Peter Sutter
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska68588, United States
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Chen Z, Hoang AT, Hwang W, Seo D, Cho M, Kim YD, Yang L, Soon A, Ahn JH, Choi HJ. Vertical Conductivity and Topography in Electrostrictive Germanium Sulfide Microribbon via Conductive Atomic Force Microscopy. NANO LETTERS 2022; 22:7636-7643. [PMID: 36106948 DOI: 10.1021/acs.nanolett.2c02763] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Layered group IV monochalcogenides are two-dimensional (2D) semiconducting materials with unique crystal structures and novel physical properties. Here, we report the growth of single crystalline GeS microribbons using the chemical vapor transport process. By using conductive atomic force microscopy, we demonstrated that the conductive behavior in the vertical direction was mainly affected by the Schottky barriers between GeS and both electrodes. Furthermore, we found that the topographic and current heterogeneities were significantly different with and without illumination. The topographic deformation and current enhancement were also predicted by our density functional theory (DFT)-based calculations. Their local spatial correlation between the topographic height and current was established. By virtue of 2D fast Fourier transform power spectra, we constructed the holistic spatial correlation between the topographic and current heterogeneity that indicated the diminished correlation with illumination. These findings on layered GeS microribbons provide insights into the conductive and topographic behaviors in 2D materials.
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Affiliation(s)
- Zhangfu Chen
- Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
| | - Anh Tuan Hoang
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Woohyun Hwang
- Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
| | - Dongjea Seo
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Minhyun Cho
- Department of Physics, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Young Duck Kim
- Department of Physics, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Lianqiao Yang
- Key Laboratory of Advanced Display and System Applications Ministry of Education, Shanghai University, Yanchang Road 149, Shanghai 200072, China
| | - Aloysius Soon
- Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
| | - Jong-Hyun Ahn
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Heon-Jin Choi
- Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
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13
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Sun Y, Jiao Z, Zandvliet HJW, Bampoulis P. Strong Fermi-Level Pinning in GeS-Metal Nanocontacts. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:11400-11406. [PMID: 35865793 PMCID: PMC9289947 DOI: 10.1021/acs.jpcc.2c02827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Germanium sulfide (GeS) is a layered monochalcogenide semiconductor with a band gap of about 1.6 eV. To verify the suitability of GeS for field-effect-based device applications, a detailed understanding of the electronic transport mechanisms of GeS-metal junctions is required. In this work, we have used conductive atomic force microscopy (c-AFM) to study charge carrier injection in metal-GeS nanocontacts. Using contact current-voltage spectroscopy, we identified three dominant charge carrier injection mechanisms: thermionic emission, direct tunneling, and Fowler-Nordheim tunneling. In the forward-bias regime, thermionic emission is the dominating current injection mechanism, whereas in the reverse-bias regime, the current injection mechanism is quantum mechanical tunneling. Using tips of different materials (platinum, n-type-doped silicon, and highly doped p-type diamond), we found that the Schottky barrier is almost independent of the work function of the metallic tip, which is indicative of a strong Fermi-level pinning. This strong Fermi-level pinning is caused by charged defects and impurities.
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14
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Wu Q, Fang Z, Zhu Y, Song H, Liu Y, Su X, Pan D, Gao Y, Wang P, Yan S, Fei Z, Yao J, Shi Y. Controllable Edge Epitaxy of Helical GeSe/GeS Heterostructures. NANO LETTERS 2022; 22:5086-5093. [PMID: 35613359 DOI: 10.1021/acs.nanolett.2c00395] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Emerging twistronics based on van der Waals (vdWs) materials has attracted great interest in condensed matter physics. Recently, more neoteric three-dimensional (3D) architectures with interlayer twist are realized in germanium sulfide (GeS) crystals. Here, we further demonstrate a convenient way for tailoring the twist rate of helical GeS crystals via tuning of the growth temperature. Under higher growth temperatures, the twist angles between successive nanoplates of the GeS mesowires (MWs) are statistically smaller, which can be understood by the dynamics of the catalyst during the growth. Moreover, we fabricate self-assembled helical heterostructures by introducing germanium selenide (GeSe) onto helical GeS crystals via edge epitaxy. Besides the helical architecture, the moiré superlattices at the twisted interfaces are also inherited. Compared with GeS MWs, helical GeSe/GeS heterostructures exhibit improved electrical conductivity and photoresponse. These results manifest new opportunities in future electronics and optoelectronics by harnessing 3D twistronics based on vdWs materials.
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Affiliation(s)
- Qi Wu
- School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, P. R. China
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Zixuan Fang
- School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu 611731, P. R. China
| | - Yuelei Zhu
- College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, P. R. China
| | - Haizeng Song
- School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, P. R. China
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Yin Liu
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States
| | - Xin Su
- School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, P. R. China
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Danfeng Pan
- School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, P. R. China
| | - Yuan Gao
- School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, P. R. China
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Peng Wang
- College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, P. R. China
| | - Shancheng Yan
- School of Geography and Biological Information, Nanjing University of Posts and Telecommunications, Nanjing 210023, P. R. China
| | - Zaiyao Fei
- School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, P. R. China
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Jie Yao
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States
| | - Yi Shi
- School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, P. R. China
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
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15
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Kong W, Zhang Y, Jiang X, Su Y, Liu H, Gao J. The quantum confinement effects on the electronic properties of monolayer GeS nanoribbon with tube-edged reconstruction. NANOTECHNOLOGY 2022; 33:345202. [PMID: 35584618 DOI: 10.1088/1361-6528/ac70e7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Monolayer α-phase GeS is promising for many novel applications due to its high carrier mobility and suitable bandgap. Recently, the metal and nonmetal zigzag edges of monolayer α-phase GeS have been predicted to undergo universal ZZ(Ge-Tube)/ZZ(S-R) edge reconstruction. Therefore, studies on GeSNR should be reconsidered. In this paper, we study the quantum confinement effects on the electronic properties of edge reconstructed monolayer GeS nanoribbon by using first-principles calculations. As width of the nanoribbon increases from 10 Å to 41 Å, the band gap keeps indirect and linearly decreases from 1.57 eV to 0.87 eV. Robust spatial separation of valence band maximum and conduction band minimum exist in reconstructed GeS nanoribbon with width larger than 19 Å. Moreover, high carrier mobility is expected in the reconstructed GeS nanoribbon. Our results suggest that reconstructed GeS nanoribbon is an important candidate for optoelectronics and photocatalytic.
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Affiliation(s)
- Weizheng Kong
- Dalian University of Technology, No.2 Linggong Road, Ganjingzi District,, Dalian, Liaoning, 116024, CHINA
| | - Yanxue Zhang
- Dalian University of Technology, No.2 Linggong Road, Ganjingzi District,, Dalian, Liaoning, 116024, CHINA
| | - Xue Jiang
- Dalian University of Technology, Key Laboratory of Materials Modification by Laser, Ion and Electron Beams,Ministry of Education, No.2 linggong road, Ganjingzi District, Dalian, Liaoning, 116024, CHINA
| | - Yan Su
- school of Physics, Dalian University of Technology, No.2 linggong road Ganjingzi District, Dalian, 116024, CHINA
| | - Hongsheng Liu
- Laboratory of Materials Modification by Laser, Ion and Electron Beams, School of Physics, Dalian University of Technology, 2 Linggong road, Ganjingzi District, Dalian, Liaoning, 116024, CHINA
| | - Junfeng Gao
- Dalian University of Technology, No.2 Linggong Road, Ganjingzi District,, Dalian, Liaoning, 116024, CHINA
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16
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Sutter E, French JS, Sutter P. Free-standing large, ultrathin germanium selenide van der Waals ribbons by combined vapor-liquid-solid growth and edge attachment. NANOSCALE 2022; 14:6195-6201. [PMID: 35393984 DOI: 10.1039/d2nr00397j] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Among group IV monochalcogenides, layered GeSe is of interest for its anisotropic properties, 1.3 eV direct band gap, ferroelectricity, high mobility, and excellent environmental stability. Electronic, optoelectronic and photovoltaic applications depend on the development of synthesis approaches that yield large quantities of crystalline flakes with controllable size and thickness. Here, we demonstrate the growth of single-crystalline GeSe nanoribbons by a vapor-liquid-solid process over Au catalyst on different substrates at low thermal budget. The nanoribbons crystallize in a layered structure, with ribbon axis along the armchair direction of the van der Waals layers. The ribbon morphology is determined by catalyst driven fast longitudinal growth accompanied by lateral expansion via edge-specific incorporation into the basal planes. This combined growth mechanism enables temperature controlled realization of ribbons with typical widths of up to 30 μm and lengths exceeding 100 μm, while maintaining sub-50 nm thickness. Nanoscale cathodoluminescence spectroscopy on individual GeSe nanoribbons demonstrates intense temperature-dependent band-edge emission up to room temperature, with fundamental bandgap and temperature coefficient of Eg(0) = 1.29 eV and α = 3.0 × 10-4 eV K-1, respectively, confirming high quality GeSe with low concentration of non-radiative recombination centers promising for optoelectronic applications including light emitters, photodetectors, and solar cells.
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Affiliation(s)
- Eli Sutter
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Jacob S French
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Peter Sutter
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
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17
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Sutter E, French JS, Komsa HP, Sutter P. 1D Germanium Sulfide van der Waals Bicrystals by Vapor-Liquid-Solid Growth. ACS NANO 2022; 16:3735-3743. [PMID: 35147417 DOI: 10.1021/acsnano.1c07349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Defects in two-dimensional and layered materials have attracted interest for realizing properties different from those of perfect crystals. Even stronger links between defect formation, fast growth, and emerging functionality can be found in nanostructures of van der Waals crystals, but only a few prevalent morphologies and defect-controlled synthesis processes have been identified. Here, we show that in vapor-liquid-solid growth of 1D van der Waals nanostructures, the catalyst controls the selection of the predominant (fast-growing) morphologies. Growth of layered GeS over Bi catalysts leads to two coexisting nanostructure types: chiral nanowires carrying axial screw dislocations and bicrystal nanoribbons where a central twin plane facilitates rapid growth. While Au catalysts produce exclusively dislocated nanowires, their modification with an additive triggers a switch to twinned bicrystal ribbons. Nanoscale spectroscopy shows that, while supporting fast growth, the twin defects in the distinctive layered bicrystals are electronically benign and free of nonradiative recombination centers.
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Affiliation(s)
- Eli Sutter
- Department of Mechanical and Materials Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, United States
| | - Jacob S French
- Department of Electrical and Computer Engineering, University of Nebraska, Lincoln, Nebraska 68588, United States
| | - Hannu-Pekka Komsa
- Faculty of Information Technology and Electrical Engineering, University of Oulu, FI-90014 Oulu, Finland
| | - Peter Sutter
- Department of Electrical and Computer Engineering, University of Nebraska, Lincoln, Nebraska 68588, United States
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18
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Sutter E, Unocic RR, Idrobo J, Sutter P. Multilayer Lateral Heterostructures of Van Der Waals Crystals with Sharp, Carrier-Transparent Interfaces. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2103830. [PMID: 34813175 PMCID: PMC8787400 DOI: 10.1002/advs.202103830] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/14/2021] [Indexed: 05/16/2023]
Abstract
Research on engineered materials that integrate different 2D crystals has largely focused on two prototypical heterostructures: Vertical van der Waals stacks and lateral heterostructures of covalently stitched monolayers. Extending lateral integration to few layer or even multilayer van der Waals crystals could enable architectures that combine the superior light absorption and photonic properties of thicker crystals with close proximity to interfaces and efficient carrier separation within the layers, potentially benefiting applications such as photovoltaics. Here, the realization of multilayer heterstructures of the van der Waals semiconductors SnS and GeS with lateral interfaces spanning up to several hundred individual layers is demonstrated. Structural and chemical imaging identifies {110} interfaces that are perpendicular to the (001) layer plane and are laterally localized and sharp on a 10 nm scale across the entire thickness. Cathodoluminescence spectroscopy provides evidence for a facile transfer of electron-hole pairs across the lateral interfaces, indicating covalent stitching with high electronic quality and a low density of recombination centers.
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Affiliation(s)
- Eli Sutter
- Department of Mechanical & Materials Engineering and Nebraska Center for Materials and NanoscienceUniversity of Nebraska‐LincolnLincolnNE68588USA
| | - Raymond R. Unocic
- Center for Nanophase Materials SciencesOak Ridge National LaboratoryOak RidgeTN37831USA
| | - Juan‐Carlos Idrobo
- Center for Nanophase Materials SciencesOak Ridge National LaboratoryOak RidgeTN37831USA
| | - Peter Sutter
- Department of Electrical & Computer EngineeringUniversity of Nebraska‐LincolnLincolnNE68588USA
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19
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20
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Sutter E, Sutter P. Ultrathin Twisted Germanium Sulfide van der Waals Nanowires by Bismuth Catalyzed Vapor-Liquid-Solid Growth. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2104784. [PMID: 34655159 DOI: 10.1002/smll.202104784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 09/18/2021] [Indexed: 06/13/2023]
Abstract
1D nanowires of 2D layered crystals are emerging nanostructures synthesized by combining van der Waals (vdW) epitaxy and vapor-liquid-solid (VLS) growth. Nanowires of the group IV monochalcogenide germanium sulfide (GeS) are of particular interest for twistronics due to axial screw dislocations giving rise to Eshelby twist and precision interlayer twist at helical vdW interfaces. Ultrathin vdW nanowires have not been realized, and it is not clear if confining layered crystals into extremely thin wires is even possible. If axial screw dislocations are still stable, ultrathin vdW nanowires can reach large twists and should display significant quantum confinement. Here it is shown that VLS growth over Bi catalysts yields vdW nanowires down to ≈15 nm diameter while maintaining tens of µm length. Combined electron microscopy and diffraction demonstrate that ultrathin GeS nanowires crystallize in the orthorhombic bulk structure but can realize nonequilibrium stacking that may lead to 1D ferroelectricity. Ultrathin nanowires carry screw dislocations, remain chiral, and achieve very high twist rates. Whenever the dislocation extends to the nanowire tip, it continues into the Bi catalyst. Eshelby twist analysis demonstrates that the ultrathin nanowires follow continuum predictions. Cathodoluminescence on individual nanowires, finally, shows pronounced emission blue shifts consistent with quantum confinement.
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Affiliation(s)
- Eli Sutter
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Peter Sutter
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
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21
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Lu W, Fang Y, Li Z, Li S, Liu S, Feng M, Xue DJ, Hu JS. Investigation of the sublimation mechanism of GeSe and GeS. Chem Commun (Camb) 2021; 57:11461-11464. [PMID: 34651148 DOI: 10.1039/d1cc03895h] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
GeSe and GeS have emerged as promising light-harvesting materials for photovoltaics due to their attractive optoelectronic properties, non-toxic and earth-abundant constituents, and excellent stability. Here we unveil the diatomic molecule sublimation mechanism of GeSe and GeS that directly guides the optimization of GeSe and GeS solar-cell fabricated via the close-space sublimation method.
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Affiliation(s)
- Wenbo Lu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. .,University of Chinese Academy of Sciences, Beijing 100149, China
| | - Yanyan Fang
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. .,University of Chinese Academy of Sciences, Beijing 100149, China
| | - Zongbao Li
- School of Material and Chemical Engineering, Tongren University, Tongren 554300, China
| | - Shumu Li
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Shunchang Liu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. .,University of Chinese Academy of Sciences, Beijing 100149, China
| | - Mingjie Feng
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. .,National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Ding-Jiang Xue
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. .,University of Chinese Academy of Sciences, Beijing 100149, China
| | - Jin-Song Hu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. .,University of Chinese Academy of Sciences, Beijing 100149, China
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22
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Zhang Y, Zhao Y, Bai Y, Gao J, Zhao J, Zhang YW. Universal Zigzag Edge Reconstruction of an α-Phase Puckered Monolayer and Its Resulting Robust Spatial Charge Separation. NANO LETTERS 2021; 21:8095-8102. [PMID: 34505776 DOI: 10.1021/acs.nanolett.1c02461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Edges are important, because they dictate the stability and properties of nanoribbons. Here, we reveal a universal reconstruction of the ZZ edge into a (2 × 1) tubed [ZZ(Tube)] edge, enabling an ultimate narrow nanotube to terminate nanoribbons for α-puckered group-V elemental and compound monolayers (GeS/Se and SnS/Se). The reconstructed edge formations are confirmed by CALYPSO. The ZZ(Tube) edge forms easily, is highly stable, and is semiconducting. Remarkably, the ZZ(Tube) edge always exhibits a type-II band structure and robust spatial charge separation. For a compound monolayer monochalcogenide, mild (2 × 1) ZZ(S-R) occurs at the chalcogenide-terminated edge. TDDFT simulations indicate that charge separation occurs only at 672 fs, while the lifetime is over 5 ns, thus facilitating robust spatial charge accumulation. These remarkable features of ZZ(Tube) edge-terminated α-puckered nanoribbons are ideal for optoelectronic and photocatalytic applications.
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Affiliation(s)
- Yanxue Zhang
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China
| | - Yanyan Zhao
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China
| | - Yizhen Bai
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China
| | - Junfeng Gao
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China
| | - Jijun Zhao
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China
| | - Yong-Wei Zhang
- Institute of High Performance Computing, A*STAR, 138632 Singapore
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23
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Yan Y, Deng Q, Li S, Guo T, Li X, Jiang Y, Song X, Huang W, Yang J, Xia C. In-plane ferroelectricity in few-layered GeS and its van der Waals ferroelectric diodes. NANOSCALE 2021; 13:16122-16130. [PMID: 34533169 DOI: 10.1039/d1nr03807a] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Two-dimensional ferroelectric semiconductors (2DFeSs) have been attracting extensive research attention on account of their unique properties and versatile applications in random-access memory, digital signal processors, and neuromorphic computing. Germanium sulfide (GeS) is predicted as a typical 2DFeS with a large spontaneous polarization of 484 pC m-1. Furthermore, the moderate band gap equivalent to 1.63 eV of GeS provides it with significant potential to create a strong bulk photovoltage in the visible light range. However, the fabrication of chemically stable few-to-monolayer GeS has not been reported so far, owing to the strong interlayer force and high chemical reactivity of the surface. Herein we demonstrate a new method for fabricating high quality, air-stable, ultrathin GeS nanoflakes. The electrical characterization confirms the formation of few-layered GeS with a remarkable in-plane ferroelectric hysteresis, which is forbidden by the inversion symmetry in bulk GeS crystals. After applying a coercive field of about 18.1 kV cm-1, a switchable shift current can also be observed in the polarized GeS nanoflakes under light irradiation. To further enhance the photoresponsivity, few-layered InSe was transferred onto the GeS nanoflakes to form van der Waals ferroelectric diodes. The interfacial perturbation breaking the inversion symmetry results in the enhancement of robust dipoles in the GeS side along the interface, which can be tuned by the in-plane electric field. Overall, this work opens the door for exploring the low-dimensional ferroelectric memory and energy conversion applications based on 2D GeS nanoflakes and provides a deeper understanding of the photovoltaic mechanism with in-plane 2D ferroelectric diodes.
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Affiliation(s)
- Yong Yan
- School of Physics, Henan Key Laboratory of Photovoltaic Materials, Henan Normal University, Henan 453007, China.
| | - Qunrui Deng
- School of Physics, Henan Key Laboratory of Photovoltaic Materials, Henan Normal University, Henan 453007, China.
| | - Shasha Li
- School of Physics, Henan Key Laboratory of Photovoltaic Materials, Henan Normal University, Henan 453007, China.
| | - Tao Guo
- Department of Mechanical and Mechatronics Engineering, Waterloo Institute for Nanotechnology, Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3Ga, Canada
| | - Xueping Li
- School of Physics, Henan Key Laboratory of Photovoltaic Materials, Henan Normal University, Henan 453007, China.
| | - Yurong Jiang
- School of Physics, Henan Key Laboratory of Photovoltaic Materials, Henan Normal University, Henan 453007, China.
| | - Xiaohui Song
- School of Physics, Henan Key Laboratory of Photovoltaic Materials, Henan Normal University, Henan 453007, China.
| | - Wen Huang
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of Science, Nanjing University of Posts and Telecommunications (NJUPT), Nanjing 2a0023, China
| | - Juehan Yang
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences & Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100083, China
| | - Congxin Xia
- School of Physics, Henan Key Laboratory of Photovoltaic Materials, Henan Normal University, Henan 453007, China.
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24
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Abstract
Two-dimensional crystals provide exceptional opportunities for integrating dissimilar materials and forming interfaces where distinct properties and phenomena emerge. To date, research has focused on two basic heterostructure types: vertical van der Waals stacks and laterally joined monolayer crystals with in-plane line interfaces. Much more diverse architectures and interface configurations can be realized in the few-layer and multilayer regime, and if mechanical stacking and single-layer growth are replaced by processes taking advantage of self-organization, conversions between polymorphs, phase separation, strain effects, and shaping into the third dimension. Here, we highlight such opportunities for engineering heterostructures, focusing on group IV chalcogenides, a class of layered semiconductors that lend themselves exceptionally well for exploring novel van der Waals architectures, as well as advanced methods including in situ microscopy during growth and nanometer-scale probes of light-matter interactions. The chosen examples point to fruitful future directions and inspire innovative developments to create unconventional van der Waals heterostructures beyond stacking.
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25
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Deng L, Yuan W, He D, Liu S, Du Y, Gong L, Liu H. Transient absorption measurements of interlayer charge transfer in a WS 2/GeS van der Waals heterostructure. Phys Chem Chem Phys 2021; 23:17259-17264. [PMID: 34346436 DOI: 10.1039/d1cp01892b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We introduce germanium sulfide (GeS) as a new layered material for the fabrication of two-dimensional van der Waals materials and heterostructures. Heterostructures of WS2/GeS were fabricated using mechanical exfoliation and dry transfer techniques. Significant photoluminescence quenching of WS2 in the heterostructures indicates efficient charge transfer. Transient absorption measurements were performed to study the dynamics of charge transfer. The results show that the heterostructure forms a type-II band alignment with the conduction band minimum and valence band maximum located in the WS2 and GeS layers, respectively. The ultrafast hole transfer from WS2 to GeS is confirmed by the faster decay of the lower peak value of the differential reflection signal in the heterostructure sample, in comparison to the WS2 monolayer. These results introduce GeS as a promising semiconductor material for developing new novel heterostructures.
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Affiliation(s)
- Lier Deng
- School of Optoelectronic Engineering, Xi'an Technological University, Xi'an 710032, China.
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Feng M, Liu SC, Hu L, Wu J, Liu X, Xue DJ, Hu JS, Wan LJ. Interfacial Strain Engineering in Wide-Bandgap GeS Thin Films for Photovoltaics. J Am Chem Soc 2021; 143:9664-9671. [PMID: 34133156 DOI: 10.1021/jacs.1c04734] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Wide-bandgap semiconductors exhibiting a bandgap of ∼1.7-1.9 eV have generated great interest recently due to their important applications in tandem solar cells as top cells and emerging indoor photovoltaics. However, concerns about the stability and toxicity especially in indoor application limit the choice of these materials. Here we report a new member of this family, germanium monosulfide (GeS); this material displays a wide bandgap of 1.7 eV, nontoxic and earth-abundant constituents, and high stability. We find that the little success of GeS solar cells to date is primarily attributed to the challenge in fabricating high-quality polycrystalline GeS films, wherein the high thermal expansion coefficient (α = 3.1 × 10-5 K-1) combined with high crystallization temperature (375 °C) of GeS induces large tensile strain in the GeS film that peels off GeS from the substrate. By introducing a high-α buffer layer between GeS and substrate, we achieve a high-quality polycrystalline GeS thin film that compactly adheres to substrate with no voids. Solar cells fabricated by these GeS films show a power conversion efficiency of 1.36% under AM 1.5G illumination (100 mW cm-2). The unencapsulated devices are stable when stored in ambient atmosphere for 1500 h. Their efficiencies further increase to 3.6% under indoor illumination of 1000 lux.
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Affiliation(s)
- Mingjie Feng
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Shun-Chang Liu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liyan Hu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Jinpeng Wu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xianhu Liu
- National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China
| | - Ding-Jiang Xue
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jin-Song Hu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Li-Jun Wan
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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Zhao S, Sun J, Yin Y, Guo Y, Liu D, Miao C, Feng X, Wang Y, Xu M, Yang ZX. In Situ Growth of GeS Nanowires with Sulfur-Rich Shell for Featured Negative Photoconductivity. J Phys Chem Lett 2021; 12:3046-3052. [PMID: 33739121 DOI: 10.1021/acs.jpclett.1c00540] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The negative photoconductivity (NPC) effect originating from the surface shell layer has been considered as an efficient approach to improve the performance of optoelectronic nanodevices. However, a scientific design and precise growth of NPC-effect-caused shell during nanowire (NW) growth process for achieving high-performance photodetectors are still lacking. In this work, GeS NWs with a controlled sulfur-rich shell, diameter, and length are successfully prepared by a simple chemical vapor deposition method. As checked by transmission electron microscopy, the thickness of the sulfur-rich shell ranges from 10.5 ± 1.5 to 13.4 ± 2.5 nm by controlling the NW growth time. The composition of the sulfur-rich shell is studied by X-ray photoelectron spectroscopy, showing the decrease of S in the GeSx shell from the surface to core. When configured into the well-known phototransistor, a featured NPC effect is observed, benefiting the high-performance photodetector with high responsivity of 105 A·W-1 and detectivity of 1012 Jones for λ = 405 nm with ultralow intensity of 0.04 mW·cm-2. However, the thicker-shell NW phototransistor shows an unstable photodetector behavior with smaller negative photocurrent because of more hole-trapping states in the thicker shell. All results suggest a careful design and controlled growth of an NPC-effect-caused shell for future optoelectronic applications.
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Affiliation(s)
- Shuai Zhao
- School of Physics, School of Microelectronics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Jiamin Sun
- School of Physics, School of Microelectronics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
| | - Yanxue Yin
- School of Physics, School of Microelectronics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Yanan Guo
- School of Physics, School of Microelectronics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Dong Liu
- School of Physics, School of Microelectronics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
| | - Chengcheng Miao
- School of Physics, School of Microelectronics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Xiao Feng
- School of Physics, School of Microelectronics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Yiming Wang
- School of Physics, School of Microelectronics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Mingsheng Xu
- School of Physics, School of Microelectronics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Zai-Xing Yang
- School of Physics, School of Microelectronics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
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Sarkar AS, Stratakis E. Dispersion behaviour of two dimensional monochalcogenides. J Colloid Interface Sci 2021; 594:334-341. [PMID: 33773385 DOI: 10.1016/j.jcis.2021.02.081] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Revised: 02/03/2021] [Accepted: 02/18/2021] [Indexed: 11/15/2022]
Abstract
Solution processable two-dimensional (2D) materials have provided an ideal platform for both fundamental studies and wearable electronic applications. Apart from graphene and 2D dichalcogenides, IVA-VI metal monochalcogenides (MMCs) has emerged recently as a promising candidate for next generation electronic applications. However, the dispersion behavior, which is crucial for the quality, solubility and stability of MMCs, has been quite unexplored. Here, the exfoliation and the dispersion behavior of Germanium (II) monosulfide (GeS) and Tin (II) monosulfide (SnS) nanosheets has been investigated in a wide range of organic solvents. Nine different organic solvents were examined and analyzed, considering the solvent polarity, surface tension, and Hansen solubility parameters. A significant yield of isolated GeS and SnS flakes, namely ~16.4 and ~23.08 μg/ml in 2-propanol and N-Methyl-2-pyrrolidone respectively were attained. The isolated flakes are few-layers nanosheets with lateral sizes over a few hundreds of nanometers. The MMC colloids exhibit long-term stability, suggesting the MMCs applicability for scalable solution processable printed electronic device applications.
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Affiliation(s)
- Abdus Salam Sarkar
- Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, Heraklion, 700 13 Crete, Greece.
| | - Emmanuel Stratakis
- Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, Heraklion, 700 13 Crete, Greece; Physics Department, University of Crete, Heraklion, 710 03 Crete, Greece.
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Yang Y, Liu SC, Li Z, Xue DJ, Hu JS. In-plane anisotropic 2D Ge-based binary materials for optoelectronic applications. Chem Commun (Camb) 2021; 57:565-575. [DOI: 10.1039/d0cc04476h] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In-plane anisotropic two-dimensional (2D) materials possess unique in-plane anisotropic physical properties arising from their low crystal lattice symmetry.
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Affiliation(s)
- Yusi Yang
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- CAS Key Laboratory of Molecular Nanostructure and Nanotechnology
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing 100190
| | - Shun-Chang Liu
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- CAS Key Laboratory of Molecular Nanostructure and Nanotechnology
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing 100190
| | - Zongbao Li
- School of Material and Chemical Engineering
- Tongren University
- Tongren 554300
- China
- National Engineering Research Center for Advanced Polymer Processing Technology
| | - Ding-Jiang Xue
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- CAS Key Laboratory of Molecular Nanostructure and Nanotechnology
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing 100190
| | - Jin-Song Hu
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- CAS Key Laboratory of Molecular Nanostructure and Nanotechnology
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing 100190
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Sarkar AS, Stratakis E. Recent Advances in 2D Metal Monochalcogenides. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:2001655. [PMID: 33173730 PMCID: PMC7610304 DOI: 10.1002/advs.202001655] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/24/2020] [Indexed: 06/11/2023]
Abstract
The family of emerging low-symmetry and structural in-plane anisotropic two-dimensional (2D) materials has been expanding rapidly in recent years. As an important emerging anisotropic 2D material, the black phosphorene analog group IVA-VI metal monochalcogenides (MMCs) have been surged recently due to their distinctive crystalline symmetries, exotic in-plane anisotropic electronic and optical response, earth abundance, and environmentally friendly characteristics. In this article, the recent research advancements in the field of anisotropic 2D MMCs are reviewed. At first, the unique wavy crystal structures together with the optical and electronic properties of such materials are discussed. The Review continues with the various methods adopted for the synthesis of layered MMCs including micromechanical and liquid phase exfoliation as well as physical vapor deposition. The last part of the article focuses on the application of the structural anisotropic response of 2D MMCs in field effect transistors, photovoltaic cells nonlinear optics, and valleytronic devices. Besides presenting the significant research in the field of this emerging class of 2D materials, this Review also delineates the existing limitations and discusses emerging possibilities and future prospects.
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Affiliation(s)
- Abdus Salam Sarkar
- Institute of Electronic Structure and LaserFoundation for Research and Technology‐HellasHeraklionCrete700 13Greece
| | - Emmanuel Stratakis
- Institute of Electronic Structure and LaserFoundation for Research and Technology‐HellasHeraklionCrete700 13Greece
- Physics DepartmentUniversity of CreteHeraklionCrete710 03Greece
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Sutter E, Wang J, Sutter P. Lateral Heterostructures of Multilayer GeS and SnS van der Waals Crystals. ACS NANO 2020; 14:12248-12255. [PMID: 32886477 DOI: 10.1021/acsnano.0c05978] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Engineered heterostructures derive distinct properties from materials integration and interface formation. Two-dimensional crystals have been combined to form vertical stacks and lateral heterostuctures with covalent line interfaces. While thicker vertical stacks have been realized, lateral heterostructures from multilayer van der Waals crystals, which could bring the benefits of high-quality interfaces to bulk-like layered materials, have remained much less explored. Here, we demonstrate the integration of anisotropic layered Sn and Ge monosulfides into complex heterostructures with seamless lateral interfaces and tunable vertical design using a two-step growth process. The anisotropic lattice mismatch at the lateral interfaces between GeS and SnS is relaxed via dislocations and interfacial alloying. Nanoscale optoelectronic measurements by cathodoluminescence spectroscopy show the characteristic light emission of joined high-quality van der Waals crystals. Spectroscopy across the lateral interface indicates valley-selective luminescence in the bulk SnS component that arises due to anisotropic electron transfer across the interface. The results demonstrate the ability to realize high-quality lateral heterostructures of multilayer van der Waals crystals for diverse applications, e.g., in optoelectronics or valleytronics.
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Affiliation(s)
- Eli Sutter
- Department of Mechanical & Materials Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Jia Wang
- Department of Mechanical & Materials Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Peter Sutter
- Department of Electrical & Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
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32
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Postorino S, Sun J, Fiedler S, Lee Cheong Lem LO, Palummo M, Camilli L. Interlayer Bound Wannier Excitons in Germanium Sulfide. MATERIALS (BASEL, SWITZERLAND) 2020; 13:ma13163568. [PMID: 32806742 PMCID: PMC7475894 DOI: 10.3390/ma13163568] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 08/04/2020] [Accepted: 08/07/2020] [Indexed: 05/05/2023]
Abstract
We report a cathodoluminescence (CL) study of layered germanium sulfide (GeS) where we observe a sharp emission peak from flakes covered with a thin hexagonal boron nitride film. GeS is a material that has recently attracted considerable interest due to its emission in the visible region and its strong anisotropy. The measured CL peak is at ~1.69 eV for samples ranging in thickness from 97 nm to 45 nm, where quantum-confinement effects can be excluded. By performing ab initio ground- and excited-state simulations for the bulk compound, we show that the measured optical peak can be unambiguously explained by radiative recombination of the first free bright bound exciton, which is due to a mixing of direct transitions near the Γ-point of the Brillouin Zone and it is associated to a very large optical anisotropy. The analysis of the corresponding excitonic wave function shows a Wannier-Mott interlayer character, being spread not only in-plane but also out-of-plane.
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Affiliation(s)
- Sara Postorino
- Dipartimento di Fisica, Università degli studi di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy;
| | - Jianbo Sun
- Department of Physics, Technical University of Denmark, Ørsteds Plads, 2800 Kgs. Lyngby, Denmark;
| | - Saskia Fiedler
- Centre for Nano Optics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark;
| | - Laurent O. Lee Cheong Lem
- Australian National Fabrication Facility, Australian National University, Canberra 2601, ACT, Australia;
| | - Maurizia Palummo
- Dipartimento di Fisica, Università degli studi di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy;
- Istituto Nazionale di Fisica Nucleare, via della Ricerca Scientifica 1, 00133 Roma, Italy
- Correspondence: (M.P.); (L.C.)
| | - Luca Camilli
- Dipartimento di Fisica, Università degli studi di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy;
- Department of Physics, Technical University of Denmark, Ørsteds Plads, 2800 Kgs. Lyngby, Denmark;
- Correspondence: (M.P.); (L.C.)
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Sutter E, French JS, Sutter S, Idrobo JC, Sutter P. Vapor-Liquid-Solid Growth and Optoelectronics of Gallium Sulfide van der Waals Nanowires. ACS NANO 2020; 14:6117-6126. [PMID: 32369332 DOI: 10.1021/acsnano.0c01919] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Nanowires of layered van der Waals (vdW) crystals are of interest due to structural characteristics and emerging properties that have no equivalent in conventional 3D crystalline nanostructures. Here, vapor-liquid-solid growth, optoelectronics, and photonics of GaS vdW nanowires are studied. Electron microscopy and diffraction demonstrate the formation of high-quality layered nanostructures with different vdW layer orientation. GaS nanowires with vdW stacking perpendicular to the wire axis have ribbon-like morphologies with lengths up to 100 μm and uniform width. Wires with axial layer stacking show tapered morphologies and a corrugated surface due to twinning between successive few-layer GaS sheets. Layered GaS nanowires are excellent wide-bandgap optoelectronic materials with Eg = 2.65 eV determined by single-nanowire absorption measurements. Nanometer-scale spectroscopy on individual nanowires shows intense blue band-edge luminescence along with longer wavelength emissions due to transitions between gap states and photonic properties such as interference of confined waveguide modes propagating within the nanowires. The combined results show promise for applications in electronics, optoelectronics, and photonics, as well as photo- or electrocatalysis owing to a high density of reactive edge sites, and intercalation-type energy storage benefiting from facile access to the interlayer vdW gaps.
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Affiliation(s)
- Eli Sutter
- Department of Mechanical & Materials Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Jacob S French
- Department of Electrical & Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Stephan Sutter
- Department of Electrical & Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Juan Carlos Idrobo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Peter Sutter
- Department of Electrical & Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
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Sun J, Giorgi G, Palummo M, Sutter P, Passacantando M, Camilli L. A Scalable Method for Thickness and Lateral Engineering of 2D Materials. ACS NANO 2020; 14:4861-4870. [PMID: 32155048 DOI: 10.1021/acsnano.0c00836] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The physical properties of two-dimensional (2D) materials depend strongly on the number of layers. Hence, methods for controlling their thickness with atomic layer precision are highly desirable, yet still too rare, and demonstrated for only a limited number of 2D materials. Here, we present a simple and scalable method for the continuous layer-by-layer thinning that works for a large class of 2D materials, notably layered germanium pnictides and chalcogenides. It is based on a simple oxidation/etching process, which selectively occurs on the topmost layers. Through a combination of atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction experiments we demonstrate the thinning method on germanium arsenide (GeAs), germanium sulfide (GeS), and germanium disulfide (GeS2). We use first-principles simulation to provide insights into the oxidation mechanism. Our strategy, which could be applied to other classes of 2D materials upon proper choice of the oxidation/etching reagent, supports 2D material-based device applications, e.g., in electronics or optoelectronics, where a precise control over the number of layers (hence over the material's physical properties) is needed. Finally, we also show that when used in combination with lithography, our method can be used to make precise patterns in the 2D materials.
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Affiliation(s)
- Jianbo Sun
- Department of Physics, Technical University of Denmark, Ørsteds Plads, 2800 Kgs. Lyngby, Denmark
| | - Giacomo Giorgi
- Dipartimento di Ingegneria Civile ed Ambientale, Università degli Studi di Perugia, via G. Duranti 93, 06125 Perugia, Italy
- Istituto di Scienze e Tecnologie Chimiche "Giulio Natta″, Consiglio Nazionale delle Ricerche, via Elce di Sotto 8, 06123 Perugia, Italy
| | - Maurizia Palummo
- Dipartimento di Fisica, Università degli studi di Roma "Tor Vergata", via della Ricerca Scientifica 1, 00133 Roma, Italy
- Istituto Nazionale di Fisica Nucleare, via della Ricerca Scientifica 1, 00133 Roma, Italy
| | - Peter Sutter
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, 1400 R St, Lincoln, Nebraska 68588, United States
| | - Maurizio Passacantando
- Department of Physical and Chemical Science, University of L'Aquila, via Vetoio, 67100 L'Aquila, Italy
- SuPerconducting and Other INnovative Materials and Devices Institute (SPIN), Department of Physical Sciences and Technologies of Matter, Consiglio Nazionale delle Ricerche, via Vetoio, 67100 L'Aquila, Italy
| | - Luca Camilli
- Department of Physics, Technical University of Denmark, Ørsteds Plads, 2800 Kgs. Lyngby, Denmark
- Dipartimento di Fisica, Università degli studi di Roma "Tor Vergata", via della Ricerca Scientifica 1, 00133 Roma, Italy
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