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Li D, Chen J, Sun T, Zhang Y, Xu J, Li W, Chen K. Enhanced subband light emission from Si quantum dots/SiO 2 multilayers via phosphorus and boron co-doping. OPTICS EXPRESS 2022; 30:12308-12315. [PMID: 35472868 DOI: 10.1364/oe.453086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 03/15/2022] [Indexed: 06/14/2023]
Abstract
Seeking light sources from Si-based materials with an emission wavelength meeting the requirements of optical telecommunication is a challenge nowadays. It was found that the subband emission centered near 1200 nm can be achieved in phosphorus-doped Si quantum dots/SiO2 multilayers. In this work, we propose the phosphorus/boron co-doping in Si quantum dots/SiO2 multilayers to enhance the subband light emission. By increasing the B co-doping ratio, the emission intensity is first increased and then decreased, while the strongest integrated emission intensity is almost two orders of magnitude stronger than that of P solely-doped sample. The enhanced subband light emission in co-doped samples can be attributed to the passivation of surface dangling bonds by B dopants. At high B co-doping ratios, the samples transfer to p-type and the subband light emission from phosphorus-related deep level is suppressed but the emission centered around 1400 nm is appeared.
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2
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Trad F, Giba AE, Devaux X, Stoffel M, Zhigunov D, Bouché A, Geiskopf S, Demoulin R, Pareige P, Talbot E, Vergnat M, Rinnert H. Influence of phosphorus on the growth and the photoluminescence properties of Si-NCs formed in P-doped SiO/SiO 2 multilayers. NANOSCALE 2021; 13:19617-19625. [PMID: 34816268 DOI: 10.1039/d1nr04765e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
This work reports on the influence of phosphorous atoms on the phase separation process and optical properties of silicon nanocrystals (Si-NCs) embedded in phosphorus doped SiO/SiO2 multilayers. Doped SiO/SiO2 multilayers with different P contents have been prepared by co-evaporation and subsequently annealed at different temperatures up to 1100 °C. The sample structure and the localization of P atoms were both studied at the nanoscale by scanning transmission electron microscopy and atom probe tomography. It is found that P incorporation modifies the mechanism of Si-NC growth by promoting the phase separation during the post-growth-annealing step, leading to nanocrystal formation at lower annealing temperatures as compared to undoped Si-NCs. Hence, the maximum of Si-NC related photoluminescence (PL) intensity is achieved for annealing temperatures lower than 900 °C. It is also demonstrated that the Si-NCs mean size increases in the presence of P, which is accompanied by a redshift of the Si-NC related emission. The influence of the phosphorus content on the PL properties is studied using both room temperature and low temperature measurements. It is shown that for a P content lower than about 0.1 at%, P atoms contribute to significantly improve the PL intensity. This effect is attributed to the P-induced-reduction of the number of non-radiative defects at the interface between Si-NCs and SiO2 matrix, which is discussed in comparison with hydrogen passivation of Si-NCs. In contrast, for increasing P contents, the PL intensity strongly decreases, which is explained by the growth of Si-NCs reaching sizes that are too large to ensure quantum confinement and to the localization of P atoms inside Si-NCs.
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Affiliation(s)
- Fatme Trad
- Université de Lorraine, CNRS, Institut Jean Lamour, F-54000 Nancy, France.
| | - Alaa E Giba
- Université de Lorraine, CNRS, Institut Jean Lamour, F-54000 Nancy, France.
- National Institute of Laser Enhanced Sciences, Cairo University, Giza 12613, Egypt
| | - Xavier Devaux
- Université de Lorraine, CNRS, Institut Jean Lamour, F-54000 Nancy, France.
| | - Mathieu Stoffel
- Université de Lorraine, CNRS, Institut Jean Lamour, F-54000 Nancy, France.
| | - Denis Zhigunov
- Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, bld. 1, 121205 Moscow, Russia
| | - Alexandre Bouché
- Université de Lorraine, CNRS, Institut Jean Lamour, F-54000 Nancy, France.
| | - Sébastien Geiskopf
- Université de Lorraine, CNRS, Institut Jean Lamour, F-54000 Nancy, France.
| | - Rémi Demoulin
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, Groupe de Physique des Matériaux, 76000 Rouen, France
| | - Philippe Pareige
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, Groupe de Physique des Matériaux, 76000 Rouen, France
| | - Etienne Talbot
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, Groupe de Physique des Matériaux, 76000 Rouen, France
| | - Michel Vergnat
- Université de Lorraine, CNRS, Institut Jean Lamour, F-54000 Nancy, France.
| | - Hervé Rinnert
- Université de Lorraine, CNRS, Institut Jean Lamour, F-54000 Nancy, France.
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3
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Milliken S, Thiessen AN, Cheong IT, O'Connor KM, Li Z, Hooper RW, Robidillo CJT, Veinot JGC. "Turning the dials": controlling synthesis, structure, composition, and surface chemistry to tailor silicon nanoparticle properties. NANOSCALE 2021; 13:16379-16404. [PMID: 34492675 DOI: 10.1039/d1nr04701a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Silicon nanoparticles (SiNPs) can be challenging to prepare with defined size, crystallinity, composition, and surface chemistry. As is the case for any nanomaterial, controlling these parameters is essential if SiNPs are to realize their full potential in areas such as alternative energy generation and storage, sensors, and medical imaging. Numerous teams have explored and established innovative synthesis methods, as well as surface functionalization protocols to control these factors. Furthermore, substantial effort has been expended to understand how the abovementioned parameters influence material properties. In the present review we provide a commentary highlighting the benefits and limitations of available methods for preparing silicon nanoparticles as well as demonstrations of tailoring optical and electronic properties through definition of structure (i.e., crystalline vs. amorphous), composition and surface chemistry. Finally, we highlight potential opportunities for future SiNP studies.
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Affiliation(s)
- Sarah Milliken
- Department of Chemistry, University of Alberta, Chemistry, Edmonton, Canada.
| | | | - I Teng Cheong
- Department of Chemistry, University of Alberta, Chemistry, Edmonton, Canada.
| | - Kevin M O'Connor
- Department of Chemistry, University of Alberta, Chemistry, Edmonton, Canada.
| | - Ziqi Li
- Department of Chemistry, University of Alberta, Chemistry, Edmonton, Canada.
| | - Riley W Hooper
- Department of Chemistry, University of Alberta, Chemistry, Edmonton, Canada.
| | | | - Jonathan G C Veinot
- Department of Chemistry, University of Alberta, Chemistry, Edmonton, Canada.
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4
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Takada M, Inoue K, Sugimoto H, Fujii M. Solution-processed silicon quantum dot photocathode for hydrogen evolution. NANOTECHNOLOGY 2021; 32:485709. [PMID: 34110304 DOI: 10.1088/1361-6528/ac09e0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 06/09/2021] [Indexed: 06/12/2023]
Abstract
The photoelectrochemical response of a photocathode made from a colloidal solution of boron (B) and phosphorus (P) codoped silicon (Si) quantum dots (QDs) 2-11 nm in diameters is studied. Since codoped Si QDs are dispersible in alcohol and water due to the hydrophilic surface, a photoelectrode with a smooth surface is produced by drop-coating the QD solution on an indium tin oxide substrate. The codoping provides high oxidation resistance to Si QDs and makes the electrode operate as a photocathode. The photoelectrochemical response of a Si QD photoelectrode depends strongly on the size of QDs; there is a transition from anodic to cathodic photocurrent around 4 nm in diameter. Below the size, anodic photocurrent due to self-oxidation of Si QDs is observed, while above the size, cathodic photocurrent due to electron transfer across the interface is observed. The cathodic photocurrent increases with increasing the size, and in some samples, it is observed for more than 3000 s under intermittent light irradiation.
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Affiliation(s)
- Miho Takada
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan
| | - Kosuke Inoue
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan
| | - Hiroshi Sugimoto
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan
| | - Minoru Fujii
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan
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5
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Pavelka O, Dyakov S, Veselý J, Fučíková A, Sugimoto H, Fujii M, Valenta J. Optimizing plasmon enhanced luminescence in silicon nanocrystals by gold nanorods. NANOSCALE 2021; 13:5045-5057. [PMID: 33646226 DOI: 10.1039/d1nr00058f] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The great application potential of photoluminescent silicon nanocrystals, especially in biomedicine, is significantly reduced due to their limited radiative rate. One of the possible ways to overcome this limitation is enhancing the luminescence by localized plasmons of metallic nanostructures. We report an optimized fabrication of gold nanorod - silicon nanocrystal core-shell nanoparticles with the silica shell as a tunable spacer. The unprecedented structural quality and homogeneity of our hybrid nanoparticles allows for detailed analysis of their luminescence. A strong correlation between dark field scattering and luminescence spectra is shown on a single particle level, indicating a dominant role of the longitudinal plasmonic band in luminescence enhancement. The spacer thickness dependence of photoluminescence intensity enhancement is investigated using a combination of experimental measurements and numerical simulations. An optimal separation distance of 5 nm is found, yielding a 7.2× enhancement of the luminescence intensity. This result is mainly attributed to an increased quantum yield resulting from the Purcell enhanced radiative rate in the nanocrystals. The ease of fabrication, low cost, long-term stability and great emission properties of the hybrid nanoparticles make them a great candidate for bio-imaging or even targeted cancer treatment.
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Affiliation(s)
- Ondřej Pavelka
- Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16, Prague, Czech Republic.
| | - Sergey Dyakov
- Photonics & Quantum Materials Center, Skolkovo Institute of Science and Technology, Nobel Street 3, Moscow 143025, Russia
| | - Jozef Veselý
- Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16, Prague, Czech Republic
| | - Anna Fučíková
- Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16, Prague, Czech Republic.
| | - Hiroshi Sugimoto
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan
| | - Minoru Fujii
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan
| | - Jan Valenta
- Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16, Prague, Czech Republic.
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6
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Jingjian Z, Pevere F, Gatty HK, Linnros J, Sychugov I. Wafer-scale fabrication of isolated luminescent silicon quantum dots using standard CMOS technology. NANOTECHNOLOGY 2020; 31:505204. [PMID: 33021208 DOI: 10.1088/1361-6528/abb556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
A wafer-scale fabrication method for isolated silicon quantum dots (Si QDs) using standard CMOS technology is presented. Reactive ion etching was performed on the device layer of a silicon-on-insulator wafer, creating nano-sized silicon islands. Subsequently, the wafer was annealed at 1100 °C for 1 h in an atmosphere of 5% H2 in Ar, forming a thin oxide passivating layer due to trace amounts of oxygen. Isolated Si QDs covering large areas (∼mm2) were revealed by photoluminescence (PL) measurements. The emission energies of such Si QDs can span over a broad range, from 1.3 to 2.0 eV and each dot is typically characterized by a single emission line at low temperatures. Most of the Si QDs exhibited a high degree of linear polarization along Si crystallographic directions [[Formula: see text]] and [[Formula: see text]]. In addition, system resolution-limited (250 μeV) PL linewidths (full width at half maximum) were measured for several Si QDs at 10 K, with no clear correlation between emission energy and polarization. The initial part of PL decays was measured at room temperature for such oxide-embedded Si QDs, approximately several microseconds long. By providing direct access to a broad size range of isolated Si QDs on a wafer, this technique paves the way for the future fabrication of photonic structures with Si QDs, which can potentially be used as single-photon sources with a long coherence length.
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Affiliation(s)
- Zhou Jingjian
- Department of Applied Physics, KTH - Royal Institute of Technology, Kista 164 40, Sweden
| | - Federico Pevere
- Department of Applied Physics, KTH - Royal Institute of Technology, Kista 164 40, Sweden
| | - Hithesh K Gatty
- Department of Applied Physics, KTH - Royal Institute of Technology, Kista 164 40, Sweden
| | - Jan Linnros
- Department of Applied Physics, KTH - Royal Institute of Technology, Kista 164 40, Sweden
| | - Ilya Sychugov
- Department of Applied Physics, KTH - Royal Institute of Technology, Kista 164 40, Sweden
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7
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Fujii M, Minami A, Sugimoto H. Precise size separation of water-soluble red-to-near-infrared-luminescent silicon quantum dots by gel electrophoresis. NANOSCALE 2020; 12:9266-9271. [PMID: 32313916 DOI: 10.1039/d0nr02764b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Gel electrophoresis, which is a standard method for separation and analysis of macromolecules such as DNA, RNA and proteins, is applied for the first time to silicon (Si) quantum dots (QDs) for size separation. In the Si QDs studied, boron (B) and phosphorus (P) are simultaneously doped. Codoping induces a negative potential on the surface of a Si QD and makes it dispersible in water. Si QDs with different B and P concentrations and grown at different temperatures (950 °C-1200 °C) are studied. It is shown that native polyacrylamide gel electrophoresis can separate codoped Si QDs by size. The capability of gel electrophoresis to immobilize size-separated QDs in a solid matrix makes detailed analyses of size-purified Si QDs possible. For example, the photoluminescence (PL) studies of the dried gel of Si QDs grown at 1100 °C demonstrate that a PL spectrum of a Si QD solution with the PL maximum around 1.4 eV can be separated into more than 15 spectra with the PL maximum changing from 1.2 to 1.8 eV depending on the migration distance. It is found that the relationship between the PL peak energy and the migration distance depends on the growth temperature of Si QDs as well as the B and P concentration. For all the samples with different impurity concentrations and grown at different temperatures, a clear trend is observed in the relationship between the full width at half maximum (FWHM) and the peak energy of the PL spectra in a wide energy range. The FWHM increases with the increasing peak energy and it is nearly twice larger than those observed for undoped Si QDs. The large PL FWHM of codoped Si QDs suggests that excitons are further localized in codoped Si QDs due to the existence of charged impurities.
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Affiliation(s)
- Minoru Fujii
- Department of Electrical and Electronic Engineering, Kobe University, 657-8501 Kobe, Japan.
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8
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Shirahata N, Nakamura J, Inoue JI, Ghosh B, Nemoto K, Nemoto Y, Takeguchi M, Masuda Y, Tanaka M, Ozin GA. Emerging Atomic Energy Levels in Zero-Dimensional Silicon Quantum Dots. NANO LETTERS 2020; 20:1491-1498. [PMID: 32046494 DOI: 10.1021/acs.nanolett.9b03157] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Driven by the emergence of colloidal semiconductor quantum dots (QDs) of tunable emission wavelengths, characteristic of exciton absorption peaks, outstanding photostability and solution processability in device fabrication have become a key tool in the development of nanomedicine and optoelectronics. Diamond cubic crystalline silicon (Si) QDs, with a diameter larger than 2 nm, terminated with hydrogen atoms are known to exhibit bulk-inherited spin and valley properties. Herein, we demonstrate a newly discovered size region of Si QDs, in which a fast radiative recombination on the order of hundreds of picoseconds is responsible for photoluminescence (PL). Despite retaining a crystallographic structure like the bulk, controlling their diameters in the 1.1-1.7 nm range realizes the strong PL with continuous spectral tunability in the 530-580 nm window, the narrow spectral line widths without emission tails, and the fast relaxation of photogenerated carriers. In contrast, QDs with diameters greater than 1.8 nm display the decay times on the microsecond order as well as the previous Si QDs. In addition to the five-orders-of-magnitude variation in the PL decay time, a systematic study on the temperature dependence of PL properties suggests that the energy structure of the smaller QDs does not retain an indirect band gap character. It is discussed that a 1.7 nm diameter is critical to undergo changes in energy structure from bulky to molecular configurations.
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Affiliation(s)
- Naoto Shirahata
- International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Japan
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0814, Japan
- Department of Physics, Chuo University, Tokyo 112-8551, Japan
| | - Jin Nakamura
- Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Nagoya 464-8601, Japan
| | - Jun-Ichi Inoue
- International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Batu Ghosh
- Department of Physics, Triveni Devi Bhalotia College, Raniganj, West Bengal 713347, India
| | - Kazuhiro Nemoto
- International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Japan
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0814, Japan
| | - Yoshihiro Nemoto
- Transmission Electron Microscopy Station, NIMS, 1-2-1, Sengen, Tsukuba 305-0047, Japan
| | - Masaki Takeguchi
- Transmission Electron Microscopy Station, NIMS, 1-2-1, Sengen, Tsukuba 305-0047, Japan
| | - Yoshitake Masuda
- National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Shimoshidami, Moriyama, Nagoya 463-8560, Japan
| | - Masahiko Tanaka
- Synchrotron X-ray Station at SPring-8, NIMS, 1-1-1 Kouto Sayo-cho Sayo-gun, Hyogo 679-5148, Japan
| | - Geoffrey A Ozin
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
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9
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Inoue A, Sugimoto H, Fujii M. Silver nanoparticles stabilized with a silicon nanocrystal shell and their antimicrobial activity. RSC Adv 2019; 9:15171-15176. [PMID: 35514861 PMCID: PMC9064261 DOI: 10.1039/c9ra02559f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 05/08/2019] [Indexed: 12/20/2022] Open
Abstract
The antimicrobial activity of a hybrid nanoparticle (NP) composed of a silver (Ag) NP core decorated with silicon (Si) nanocrystals (NCs) on the exterior (Ag/Si NPs) is evaluated. The shell of Si NCs effectively protects the surface of Ag NPs, thus the particles are more stable in water and in air compared to conventional organic-capped Ag NPs. The bacterial growth kinetic analysis reveals that the Si NC shell does not suppress the release of Ag ions from the Ag NP surface due probably to the porous structure. For the antimicrobial coating application, a thin film of the hybrid Ag/Si NPs is produced by drop coating the solution on a cover glass. Thanks to the Si NC shell, agglomeration of Ag NPs in the film is prevented and the film shows a very similar optical absorption spectrum to that of the solution. The film exhibits a larger zone of inhibition in an agar diffusion assay of Escherichia coli compared to a film produced from organic-capped Ag NPs.
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Affiliation(s)
- Asuka Inoue
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University Rokkodai, Nada Kobe 657-8501 Japan
| | - Hiroshi Sugimoto
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University Rokkodai, Nada Kobe 657-8501 Japan
| | - Minoru Fujii
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University Rokkodai, Nada Kobe 657-8501 Japan
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10
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Somogyi B, Bruyer E, Gali A. Photoluminescence, infrared, and Raman spectra of co-doped Si nanoparticles from first principles. J Chem Phys 2018; 149:154702. [PMID: 30342438 DOI: 10.1063/1.5053100] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Co-doped silicon nanoparticles (NPs) are promising for the realization of novel biological and optoelectronic applications. Despite the scientific and technological interest, the structure of heavily co-doped Si NPs is still not very well understood. By means of first principles simulations, various spectroscopic quantities can be computed and compared to the corresponding experimental data. In this paper, we demonstrate that the calculated infrared spectra, photoluminescence spectra, and Raman spectra can provide valuable insights into the atomistic structure of co-doped Si NPs.
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Affiliation(s)
- Bálint Somogyi
- Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary
| | - Emilie Bruyer
- Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary
| | - Adam Gali
- Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary
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11
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Kano S, Tada Y, Matsuda S, Fujii M. Solution Processing of Hydrogen-Terminated Silicon Nanocrystal for Flexible Electronic Device. ACS APPLIED MATERIALS & INTERFACES 2018; 10:20672-20678. [PMID: 29808665 DOI: 10.1021/acsami.8b04072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We demonstrate solution processing of hydrogen-terminated silicon nanocrystals (H-Si NCs) for flexible electronic devices. To obtain high and uniform conductivity of a solution-processed Si NC film, we adopt a perfectly dispersed colloidal H-Si NC solution. We show a high conductivity (2 × 10-5 S/cm) of a solution-processed H-Si NC film which is spin-coated in air. The NC film (area: 100 mm2) has uniform conductivity and responds to laser irradiation with 6.8 and 24.1 μs of rise and fall time. By using time-of-flight measurements, we propose a charge transport model in the H-Si NC film. For the proof-of-concept of this study, a flexible photodetector on a polyethylene terephthalate substrate is demonstrated by spin-coating colloidal H-Si NC solution in air. The photodetector can be bent in 5.9 mm bending radius at smallest, and the device properly works after being bent in 2500 cycles.
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Affiliation(s)
- Shinya Kano
- Department of Electrical and Electronic Engineering, Graduate School of Engineering , Kobe University , Rokkodai, Nada, Kobe 657-8501 , Japan
| | - Yasuhiro Tada
- Department of Electrical and Electronic Engineering, Graduate School of Engineering , Kobe University , Rokkodai, Nada, Kobe 657-8501 , Japan
| | - Satoshi Matsuda
- Department of Electrical and Electronic Engineering, Graduate School of Engineering , Kobe University , Rokkodai, Nada, Kobe 657-8501 , Japan
| | - Minoru Fujii
- Department of Electrical and Electronic Engineering, Graduate School of Engineering , Kobe University , Rokkodai, Nada, Kobe 657-8501 , Japan
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12
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Sugimoto H, Yamamura M, Sakiyama M, Fujii M. Visualizing a core-shell structure of heavily doped silicon quantum dots by electron microscopy using an atomically thin support film. NANOSCALE 2018; 10:7357-7362. [PMID: 29637958 DOI: 10.1039/c7nr09474d] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We successfully visualize a core-shell structure of a heavily B and P codoped Si quantum dot (QD) by transmission electron microscopy using an ultra-thin graphene oxide support film. The enhanced contrast reveals that a codoped Si QD has a highly crystalline Si core and an amorphous shell composed of Si, B and P.
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Affiliation(s)
- Hiroshi Sugimoto
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan.
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13
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Ohata Y, Sugimoto H, Fujii M. Assembling silicon quantum dots into wires, networks and rods via metal ion bridges. NANOSCALE 2018; 10:7597-7604. [PMID: 29638232 DOI: 10.1039/c8nr00631h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Wires and networks of Si quantum dots (QDs) with a length of over 1 μm and a width of ∼30 nm are produced by bridging Si QDs with metal ions in solution. It is shown that the width of the wires is almost independent of the preparation parameters and is always about 30 nm, except for the case when Si QDs larger than 30 nm are used, while the length of the wires depends strongly on the kinds of ions, the amount of ions and the amount of Si QDs in a solution. In addition to the microscopic size assemblies, macroscopic size rods of Si QDs with a width of ∼20 μm are produced by using Zn2+ ions. The XPS analyses reveal that Si QDs are connected to each other via a ZnO layer in the rod. The rods have much higher conductivity and photo-response than Si QD solids produced without metal ions.
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Affiliation(s)
- Yuki Ohata
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan.
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14
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Fujii M, Sugimoto H, Kano S. Silicon quantum dots with heavily boron and phosphorus codoped shell. Chem Commun (Camb) 2018; 54:4375-4389. [DOI: 10.1039/c8cc01612g] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Heavily boron and phosphorus codoped silicon quantum dots (QDs) are dispersible in water without organic ligands and exhibit near infrared luminescence. We summarize the fundamental properties and demonstrate the formation of a variety of nanocomposites.
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Affiliation(s)
- Minoru Fujii
- Department of Electrical and Electronic Engineering
- Graduate School of Engineering
- Kobe University
- Kobe 657-8501
- Japan
| | - Hiroshi Sugimoto
- Department of Electrical and Electronic Engineering
- Graduate School of Engineering
- Kobe University
- Kobe 657-8501
- Japan
| | - Shinya Kano
- Department of Electrical and Electronic Engineering
- Graduate School of Engineering
- Kobe University
- Kobe 657-8501
- Japan
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15
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Derian R, Tokár K, Somogyi B, Gali Á, Štich I. Optical Gaps in Pristine and Heavily Doped Silicon Nanocrystals: DFT versus Quantum Monte Carlo Benchmarks. J Chem Theory Comput 2017; 13:6061-6067. [PMID: 29083915 DOI: 10.1021/acs.jctc.7b00823] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present a time-dependent density functional theory (TDDFT) study of the optical gaps of light-emitting nanomaterials, namely, pristine and heavily B- and P-codoped silicon crystalline nanoparticles. Twenty DFT exchange-correlation functionals sampled from the best currently available inventory such as hybrids and range-separated hybrids are benchmarked against ultra-accurate quantum Monte Carlo results on small model Si nanocrystals. Overall, the range-separated hybrids are found to perform best. The quality of the DFT gaps is correlated with the deviation from Koopmans' theorem as a possible quality guide. In addition to providing a generic test of the ability of TDDFT to describe optical properties of silicon crystalline nanoparticles, the results also open up a route to benchmark-quality DFT studies of nanoparticle sizes approaching those studied experimentally.
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Affiliation(s)
- R Derian
- Center for Computational Materials Science, Institute of Physics, Slovak Academy of Sciences , 84511 Bratislava, Slovakia
| | - K Tokár
- Center for Computational Materials Science, Institute of Physics, Slovak Academy of Sciences , 84511 Bratislava, Slovakia
| | - B Somogyi
- Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, Hungarian Academy of Sciences , Budapest, Hungary
| | - Á Gali
- Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, Hungarian Academy of Sciences , Budapest, Hungary.,Department of Atomic Physics, Budapest University of Technology and Economics , Budafoki út 8., H-1111 Budapest, Hungary
| | - I Štich
- Center for Computational Materials Science, Institute of Physics, Slovak Academy of Sciences , 84511 Bratislava, Slovakia.,Department of Natural Sciences, University of Ss. Cyril and Methodius , 91701 Trnava, Slovakia
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Silicon Nanocrystals with pH-Sensitive Tunable Light Emission from Violet to Blue-Green. SENSORS 2017; 17:s17102396. [PMID: 29053627 PMCID: PMC5677222 DOI: 10.3390/s17102396] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 10/12/2017] [Accepted: 10/20/2017] [Indexed: 02/02/2023]
Abstract
We fabricated a silicon nanocrystal (NC) suspension with visible, continuous, tunable light emission with pH sensitivity from violet to blue-green. Transmission electron microscopy (TEM) images and X-ray diffraction (XRD) pattern analysis exhibit the highly crystalline nanoparticles of silicon. Photoluminescence (PL) spectra and photoluminescence excitation (PLE) spectra at different pH values, such as 1, 3, 5, 7, 9, and 11, reveal the origins of light emission from the silicon NC suspension, which includes both the quantum confinement effect and surface bonding. The quantum confinement effect dominates the PL origins of silicon NCs, especially determining the tunability and the emission range of PL, while the surface bonding regulates the maximum peak center, full width at half maximum (FWHM), and offsets of PL peaks in response to the changing pH value. The peak fitting of PLE curves reveals one of the divided PLE peaks shifts towards a shorter wavelength when the pH value increases, which implies correspondence with the surface bonding between silicon NCs and hydrogen atoms or hydroxyl groups. The consequent detailed analysis of the PL spectra indicates that the surface bonding results in the transforming of the PL curves towards longer wavelengths with the increasing pH values, which is defined as the pH sensitivity of PL. These results suggest that the present silicon NCs with pH-sensitive tunable light emission could find promising potential applications as optical sources, bio-sensors, etc.
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Kano S, Kim K, Fujii M. Fast-Response and Flexible Nanocrystal-Based Humidity Sensor for Monitoring Human Respiration and Water Evaporation on Skin. ACS Sens 2017; 2:828-833. [PMID: 28723119 DOI: 10.1021/acssensors.7b00199] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We develop a fast-response and flexible nanocrystal-based humidity sensor for real-time monitoring of human activity: respiration and water evaporation on skin. A silicon-nanocrystal film is formed on a polyimide film by spin-coating the colloidal solution and is used as a flexible and humidity-sensitive material in a humidity sensor. The flexible nanocrystal-based humidity sensor shows a high sensitivity; current through the nanocrystal film changes by 5 orders of magnitude in the relative humidity range of 8-83%. The response/recovery time of the sensor is 40 ms. Thanks to the fast response and recovery time, the sensor can monitor human respiration and water evaporation on skin in real time. Due to the flexibility and the fast response/recovery time, the sensor is promising for application in personal health monitoring as well as environmental monitoring.
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Affiliation(s)
- Shinya Kano
- Department of Electrical
and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan
| | - Kwangsoo Kim
- Department of Electrical
and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan
| | - Minoru Fujii
- Department of Electrical
and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan
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Sugimoto H, Ozaki Y, Fujii M. Silicon Quantum Dots in Dielectric Scattering Media: Broadband Enhancement of Effective Absorption Cross Section by Light Trapping. ACS APPLIED MATERIALS & INTERFACES 2017; 9:19135-19142. [PMID: 28513134 DOI: 10.1021/acsami.7b04292] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report strong enhancements of the effective absorption cross section and photoluminescence (PL) intensity of silicon quantum dots (Si QDs) with 2.8-6.8 nm in diameter in a highly scattering dielectric medium. The scattering medium is a polymer thin film with submicrometer size pores inside, supporting the resonant cavity modes in the visible range. By the scattering associated with the cavity modes, efficient light trapping into a polymer film with ∼1 μm in thickness is achieved, which leads to 30-40 times enhancement of the effective absorption cross section of embedded Si QDs in a green-red wavelength range. The scattering medium can also enhance up to 40 times the PL of QDs. Detailed analysis reveals that the enhancements of the extraction efficiency as well as the excitation efficiency contribute to the PL enhancement.
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Affiliation(s)
- Hiroshi Sugimoto
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University , Rokkodai, Nada, Kobe 657-8501, Japan
| | - Yusuke Ozaki
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University , Rokkodai, Nada, Kobe 657-8501, Japan
| | - Minoru Fujii
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University , Rokkodai, Nada, Kobe 657-8501, Japan
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Sychugov I, Valenta J, Linnros J. Probing silicon quantum dots by single-dot techniques. NANOTECHNOLOGY 2017; 28:072002. [PMID: 27980232 DOI: 10.1088/1361-6528/aa542b] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Silicon nanocrystals represent an important class of non-toxic, heavy-metal free quantum dots, where the high natural abundance of silicon is an additional advantage. Successful development in mass-fabrication, starting from porous silicon to recent advances in chemical and plasma synthesis, opens up new possibilities for applications in optoelectronics, bio-imaging, photovoltaics, and sensitizing areas. In this review basic physical properties of silicon nanocrystals revealed by photoluminescence spectroscopy, lifetime, intensity trace and electrical measurements on individual nanoparticles are summarized. The fabrication methods developed for accessing single Si nanocrystals are also reviewed. It is concluded that silicon nanocrystals share many of the properties of direct bandgap nanocrystals exhibiting sharp emission lines at low temperatures, on/off blinking, spectral diffusion etc. An analysis of reported results is provided in comparison with theory and with direct bandgap material quantum dots. In addition, the role of passivation and inherent interface/matrix defects is discussed.
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Affiliation(s)
- Ilya Sychugov
- Materials and Nano Physics Department, KTH-Royal Institute of Technology, Kista, Stockholm, SE-16440, Sweden
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Ni Z, Jia H, Pi X, Yang D. Density functional theory study on the boron and phosphorus doping of germanium quantum dots. RSC Adv 2017. [DOI: 10.1039/c7ra09008k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Doping is a crucial way of tuning the properties of semiconductor quantum dots (QDs). The current theoretical work explained the experimental findings on the doping of germanium (Ge) QDs and predicted the properties of doped Ge QDs.
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Affiliation(s)
- Zhenyi Ni
- State Key Laboratory of Silicon Materials
- School of Materials Science and Engineering
- Zhejiang University
- Hangzhou
- China
| | - Hui Jia
- State Key Laboratory of Silicon Materials
- School of Materials Science and Engineering
- Zhejiang University
- Hangzhou
- China
| | - Xiaodong Pi
- State Key Laboratory of Silicon Materials
- School of Materials Science and Engineering
- Zhejiang University
- Hangzhou
- China
| | - Deren Yang
- State Key Laboratory of Silicon Materials
- School of Materials Science and Engineering
- Zhejiang University
- Hangzhou
- China
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