1
|
Sutter E, Kisslinger K, Unocic RR, Burns K, Hachtel J, Sutter P. Photonics in Multimaterial Lateral Heterostructures Combining Group IV Chalcogenide van der Waals Semiconductors. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2307372. [PMID: 38054819 DOI: 10.1002/smll.202307372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 11/25/2023] [Indexed: 12/07/2023]
Abstract
Lateral heterostructures combining two multilayer group IV chalcogenide van der Waals semiconductors have attracted interest for optoelectronics, twistronics, and valleytronics, owing to their structural anisotropy, bulk-like electronic properties, enhanced optical thickness, and vertical interfaces enabling in-plane charge manipulation/separation, perpendicular to the trajectory of incident light. Group IV monochalcogenides support propagating photonic waveguide modes, but their interference gives rise to complex light emission patterns throughout the visible/near-infrared range both in uniform flakes and single-interface lateral heterostructures. Here, this work demonstrates the judicious integration of pure and alloyed monochalcogenide crystals into multimaterial heterostructures with unique photonic properties, notably the ability to select photonic modes with targeted discrete energies through geometric factors rather than band engineering. SnS-GeS1-xSex-GeSe-GeS1-xSex heterostructures with a GeS1-xSex active layer sandwiched laterally between GeSe and SnS, semiconductors with similar optical constants but smaller bandgaps, were designed and realized via sequential vapor transport synthesis. Raman spectroscopy, electron microscopy/diffraction, and energy-dispersive X-ray spectroscopy confirm a high crystal quality of the laterally stitched components with sharp interfaces. Nanometer-scale cathodoluminescence spectroscopy provides evidence for a facile transfer of electron-hole pairs across the lateral interfaces and demonstrates the selection of photon emission at discrete energies in the laterally embedded active (GeS1- xSex) part of the heterostructure.
Collapse
Affiliation(s)
- Eli Sutter
- Department of Mechanical & Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| | - Kim Kisslinger
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Raymond R Unocic
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
| | - Kory Burns
- Department of Materials Science & Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Jordan Hachtel
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
| | - Peter Sutter
- Department of Electrical & Computer Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA
| |
Collapse
|
2
|
Wu Z, Liu Y, Wang D, Zhang Y, Gu K, He Z, Liu L, Liu H, Fan J, Chen C, Wang S. Cu@Co with Dilatation Strain for High-Performance Electrocatalytic Reduction of Low-Concentration Nitric Oxide. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023:e2309470. [PMID: 38113301 DOI: 10.1002/adma.202309470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 12/06/2023] [Indexed: 12/21/2023]
Abstract
Electrocatalytic reduction of nitric oxide (NO) to ammonia (NH3 ) is a clean and sustainable strategy to simultaneously remove NO and synthesize NH3 . However, the conversion of low concentration NO to NH3 is still a huge challenge. In this work, the dilatation strain between Cu and Co interface over Cu@Co catalyst is built up and investigated for electroreduction of low concentration NO (volume ratio of 1%) to NH3 . The catalyst shows a high NH3 yield of 627.20 µg h-1 cm-2 and a Faradaic efficiency of 76.54%. Through the combination of spherical aberration-corrected transmission electron microscopy and geometric phase analyses, it shows that Co atoms occupy Cu lattice sites to form dilatation strain in the xy direction within Co region. Further density functional theory calculations and NO temperature-programmed desorption (NO-TPD) results show that the surface dilatation strain on Cu@Co is helpful to enhance the NO adsorption and reduce energy barrier of the rate-determining step (*NO to *NOH), thereby accelerating the catalytic reaction. To simultaneously realize NO exhaust gas removal, NH3 green synthesis, and electricity output, a Zn-NO battery with Cu@Co cathode is assembled with a power density of 3.08 mW cm-2 and an NH3 yield of 273.37 µg h-1 cm-2 .
Collapse
Affiliation(s)
- Ze Wu
- College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha, Hunan, 410114, P. R. China
| | - Yujing Liu
- College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha, Hunan, 410114, P. R. China
| | - Dongdong Wang
- State Key Laboratory of Chem/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, the National Supercomputer Centers in Changsha, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Yiqiong Zhang
- College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha, Hunan, 410114, P. R. China
| | - Kaizhi Gu
- Institute for Advanced Study, Central South University, Changsha, 410083, P. R. China
| | - Zejin He
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, P. R. China
| | - Limin Liu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, P. R. China
| | - Hanwen Liu
- WA School of Mines, Minerals, Energy and Chemical Engineering (WASM-MECE), Curtin University, Perth, WA, 6102, Australia
| | - Jincheng Fan
- College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha, Hunan, 410114, P. R. China
| | - Chen Chen
- State Key Laboratory of Chem/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, the National Supercomputer Centers in Changsha, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Shuangyin Wang
- State Key Laboratory of Chem/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, the National Supercomputer Centers in Changsha, Hunan University, Changsha, Hunan, 410082, P. R. China
| |
Collapse
|
3
|
Sutter P, Komsa HP, Kisslinger K, Sutter E. Lateral Integration of SnS and GeSe van der Waals Semiconductors: Interface Formation, Electronic Structure, and Nanoscale Optoelectronics. ACS NANO 2023; 17:9552-9564. [PMID: 37144978 DOI: 10.1021/acsnano.3c02411] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The emergence of atomically thin crystals has allowed extending materials integration to lateral heterostructures where different 2D materials are covalently connected in the plane. The concept of lateral heterostructures can be generalized to thicker layered crystals, provided that a suitably faceted seed crystal presents edges to which a compatible second van der Waals material can be attached layer by layer. Here, we examine the possibility of integrating multilayer crystals of the group IV monochalcogenides SnS and GeSe, which have the same crystal structure, small lattice mismatch, and similar bandgaps. In a two-step growth process, lateral epitaxy of GeSe on the sidewalls of multilayer SnS flakes (obtained by vapor transport of a SnS2 precursor on graphite) yields heterostructures of laterally stitched crystalline GeSe and SnS without any detectable vertical overgrowth of the SnS seeds and with sharp lateral interfaces. Combined cathodoluminescence spectroscopy and ab initio calculations show the effects of small band offsets on carrier transport and radiative recombination near the interface. The results demonstrate the possibility of forming atomically connected lateral interfaces across many van der Waals layers, which is promising for manipulating optoelectronics, photonics, and for managing charge- and thermal transport.
Collapse
Affiliation(s)
- Peter Sutter
- Department of Electrical & Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Hannu-Pekka Komsa
- Microelectronics Research Unit, University of Oulu, FI-90014 Oulu, Finland
| | - Kim Kisslinger
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Eli Sutter
- Department of Mechanical & Materials Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| |
Collapse
|
4
|
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.
Collapse
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
| |
Collapse
|
5
|
Luan Y, Zobeiri H, Wang X, Sutter E, Sutter P, Fei Z. Imaging Anisotropic Waveguide Exciton Polaritons in Tin Sulfide. NANO LETTERS 2022; 22:1497-1503. [PMID: 35133843 DOI: 10.1021/acs.nanolett.1c03833] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
In recent years, novel materials supporting in-plane anisotropic polaritons have attracted a great deal of research interest due to their capability of shaping nanoscale field distributions and controlling nanophotonic energy flows. Here we report a nano-optical imaging study of waveguide exciton polaritons (EPs) in tin sulfide (SnS) in the near-infrared (near-IR) region using scattering-type scanning near-field optical microscopy (s-SNOM). With s-SNOM, we mapped in real space the propagative EPs in SnS, which show sensitive dependence on the excitation energy and sample thickness. Moreover, we found that both the polariton wavelength and propagation length are anisotropic in the sample plane. In particular, in a narrow spectral range from 1.32 to 1.44 eV, the EPs demonstrate quasi-one-dimensional propagation, which is rarely seen in natural polaritonic materials. A further analysis indicates that the observed polariton anisotropy originates from the different optical band gaps and exciton binding energies along the two principal crystal axes of SnS.
Collapse
Affiliation(s)
- Yilong Luan
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, United States
- Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, United States
| | - Hamidreza Zobeiri
- Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011, United States
| | - Xinwei Wang
- Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011, United States
| | - 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
| | - Peter Sutter
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Zhe Fei
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, United States
- Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, United States
| |
Collapse
|
6
|
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.
Collapse
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
| |
Collapse
|
7
|
Zi Y, Zhu J, Hu L, Wang M, Huang W. Nanoengineering of Tin Monosulfide (SnS)‐Based Structures for Emerging Applications. SMALL SCIENCE 2021. [DOI: 10.1002/smsc.202100098] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- You Zi
- School of Chemistry and Chemical Engineering Nantong University Nantong Jiangsu 226019 P. R. China
| | - Jun Zhu
- School of Chemistry and Chemical Engineering Nantong University Nantong Jiangsu 226019 P. R. China
| | - Lanping Hu
- School of Chemistry and Chemical Engineering Nantong University Nantong Jiangsu 226019 P. R. China
| | - Mengke Wang
- School of Chemistry and Chemical Engineering Nantong University Nantong Jiangsu 226019 P. R. China
| | - Weichun Huang
- School of Chemistry and Chemical Engineering Nantong University Nantong Jiangsu 226019 P. R. China
| |
Collapse
|
8
|
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.
Collapse
|
9
|
Li S, Wang Y, Cheng P, Feng B, Chen L, Wu K. Realization of Large Scale, 2D van der Waals Heterojunction of SnS 2 /SnS by Reversible Sulfurization. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2101154. [PMID: 34331375 DOI: 10.1002/smll.202101154] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 05/25/2021] [Indexed: 06/13/2023]
Abstract
2D van der Waals heterojunction provides an attractive opportunity for realizing novel electronic or optoelectronic devices. It remains challenging to realize high-quality heterostructures through scalable methods such as molecular epitaxy growth (MBE). Here, growth of few-layer SnS thin films is reported on mica and Nb-doped SrTiO3 (100) substrates by MBE. Then the top layer of SnS film is uniformly sulfurized to monolayer SnS2 in a sulfur atmosphere, resulting in a high-quality SnS2 /SnS 2D heterojunction. Furthermore, the SnS2 layer can be recovered to SnS by annealing SnS2 /SnS without sulfur supply, indicating the heterojunction formation is reversible. The scanning tunneling spectroscopy measurements on SnS2 /SnS heterostructure indicate the type-II band alignment in SnS2 /SnS. The work provides a promising approach to construct artificial 2D heterojunctions with desired properties, which could be extended to other sulfide and selenide systems.
Collapse
Affiliation(s)
- Shuhui Li
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Yu Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Peng Cheng
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Baojie Feng
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Lan Chen
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Kehui Wu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| |
Collapse
|
10
|
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.
Collapse
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.
| |
Collapse
|
11
|
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.
Collapse
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
| |
Collapse
|
12
|
Vovk IA, Lobanov VV, Litvin AP, Leonov MY, Fedorov AV, Rukhlenko ID. Band Structure and Intersubband Transitions of Three-Layer Semiconductor Nanoplatelets. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:nano10050933. [PMID: 32408535 PMCID: PMC7279220 DOI: 10.3390/nano10050933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 04/29/2020] [Accepted: 05/07/2020] [Indexed: 06/11/2023]
Abstract
This paper presents the first general theory of electronic band structure and intersubband transitions in three-layer semiconductor nanoplatelets. We find a dispersion relation and wave functions of the confined electrons and use them to analyze the band structure of core/shell nanoplatelets with equal thicknesses of the shell layers. It is shown that the energies of electrons localized inside the shell layers can be degenerate for certain electron wave vectors and certain core and shell thicknesses. We also show that the energies of intersubband transitions can be nonmonotonic functions of the core and shell thicknesses, exhibiting pronounced local minima and maxima which can be observed in the infrared absorption spectra. Our results will prove useful for the design of photonic devices based on multilayered semiconductor nanoplatelets operating at infrared frequencies.
Collapse
Affiliation(s)
- Ilia A. Vovk
- ITMO University, Center of Information Optical Technology, Saint Petersburg 197101, Russia; (I.A.V.); (V.V.L.); (A.P.L.); (M.Y.L.); (A.V.F.)
| | - Vladimir V. Lobanov
- ITMO University, Center of Information Optical Technology, Saint Petersburg 197101, Russia; (I.A.V.); (V.V.L.); (A.P.L.); (M.Y.L.); (A.V.F.)
| | - Aleksandr P. Litvin
- ITMO University, Center of Information Optical Technology, Saint Petersburg 197101, Russia; (I.A.V.); (V.V.L.); (A.P.L.); (M.Y.L.); (A.V.F.)
| | - Mikhail Yu. Leonov
- ITMO University, Center of Information Optical Technology, Saint Petersburg 197101, Russia; (I.A.V.); (V.V.L.); (A.P.L.); (M.Y.L.); (A.V.F.)
| | - Anatoly V. Fedorov
- ITMO University, Center of Information Optical Technology, Saint Petersburg 197101, Russia; (I.A.V.); (V.V.L.); (A.P.L.); (M.Y.L.); (A.V.F.)
| | - Ivan D. Rukhlenko
- The University of Sydney, Institute of Photonics and Optical Science (IPOS), School of Physics, Camperdown, NSW 2006, Australia
| |
Collapse
|
13
|
Self-organized twist-heterostructures via aligned van der Waals epitaxy and solid-state transformations. Nat Commun 2019; 10:5528. [PMID: 31797928 PMCID: PMC6893034 DOI: 10.1038/s41467-019-13488-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 11/07/2019] [Indexed: 11/29/2022] Open
Abstract
Vertical van der Waals (vdW) heterostructures of 2D crystals with defined interlayer twist are of interest for band-structure engineering via twist moiré superlattice potentials. To date, twist-heterostructures have been realized by micromechanical stacking. Direct synthesis is hindered by the tendency toward equilibrium stacking without interlayer twist. Here, we demonstrate that growing a 2D crystal with fixed azimuthal alignment to the substrate followed by transformation of this intermediate enables a potentially scalable synthesis of twisted heterostructures. Microscopy during growth of ultrathin orthorhombic SnS on trigonal SnS2 shows that vdW epitaxy yields azimuthal order even for non-isotypic 2D crystals. Excess sulfur drives a spontaneous transformation of the few-layer SnS to SnS2, whose orientation – rotated 30° against the underlying SnS2 crystal – is defined by the SnS intermediate rather than the substrate. Preferential nucleation of additional SnS on such twisted domains repeats the process, promising the realization of complex twisted stacks by bottom-up synthesis. Vertically stacked twisted layers of two-dimensional materials can trigger exciting fundamental physics. Here, authors report controlled growth of 30° twisted few-layer SnS2 over SnS2 via van der Waals epitaxy of an SnS intermediate and its transformation in the presence of excess sulfur.
Collapse
|
14
|
Luican-Mayer A, Zhang Y, DiLullo A, Li Y, Fisher B, Ulloa SE, Hla SW. Negative differential resistance observed on the charge density wave of a transition metal dichalcogenide. NANOSCALE 2019; 11:22351-22358. [PMID: 31728463 DOI: 10.1039/c9nr07857f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Charge density waves and negative differential resistance are seemingly unconnected physical phenomena. The former is an ordered quantum fluid of electrons, intensely investigated for its relation with superconductivity, while the latter receives much attention for its potential applications in electronics. Here we show that these two phenomena can not only coexist but also that the localized electronic states of the charge density wave are essential to induce negative differential resistance in a transition metal dichalcogenide, 1T-TaS2. Using scanning tunneling microscopy and spectroscopy, we report the observation of negative differential resistance in the commensurate charge density wave state of 1T-TaS2. The observed phenomenon is explained by the interplay of interlayer and intra-layer tunneling with the participation of the atomically localized states of the charge density wave maxima and minima. We demonstrate that lattice defects can locally affect the coupling between the layers and are therefore a mechanism to realize NDR in these materials.
Collapse
Affiliation(s)
- Adina Luican-Mayer
- Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Ave., Argonne, Illinois 60439, USA.
| | | | | | | | | | | | | |
Collapse
|
15
|
Sutter E, Zhang B, Sun M, Sutter P. Few-Layer to Multilayer Germanium(II) Sulfide: Synthesis, Structure, Stability, and Optoelectronics. ACS NANO 2019; 13:9352-9362. [PMID: 31305983 DOI: 10.1021/acsnano.9b03986] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Among 2D/layered semiconductors, group IV monochalcogenides such as SnS(e) and GeS(e) have attracted attention as phosphorene/black phosphorus analogues with anisotropic structures and predicted unusual properties. In contrast to SnS, for which bottom-up synthesis has been reported, few-layer GeS has been realized primarily via exfoliation from bulk crystals. Here, we report the synthesis of large (up to >20 μm), faceted single crystalline GeS flakes with anisotropic properties using a vapor transport process. In situ electron microscopy is used to identify the thermal stability and sublimation pathways, and demonstrates that the GeS flakes are self-encapsulated in a thin, sulfur-rich amorphous GeSx shell during growth. The shell provides exceptional chemical stability to the layered GeS core. In contrast to exfoliated GeS, which rapidly degrades during exposure to air, the synthesized GeS-GeSx core-shell structures show no signs of chemical attack and remain unchanged in air for extended time periods. Measurements of the optoelectronic properties by photoluminescence spectroscopy show a tunable bandgap due to out-of-plane quantum confinement in flakes with thickness below 100 nm. Cathodoluminescence (CL) spectroscopy with nanoscale excitation provides evidence for interfacial charge transfer due to a type II heterojunction between the crystalline core and amorphous shell. Measurements by locally excited CL yield a minority carrier (electron) diffusion length in the p-type GeS core ldiff = 0.27 μm, on par with diffusion lengths in the highest-quality layered chalcogenide semiconductors.
Collapse
Affiliation(s)
- Eli Sutter
- Department of Mechanical and Materials Engineering , University of Nebraska-Lincoln , Lincoln , Nebraska 68588 , United States
| | - Bo Zhang
- Department of Mechanical and Materials Engineering , University of Nebraska-Lincoln , Lincoln , Nebraska 68588 , United States
| | - Muhua Sun
- 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
| |
Collapse
|