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We are researching semiconductor materials with potential applications in photonics by making full use of film formation methods that enable the fabrication of high-quality semiconductor crystals.

In particular, we are studying the physical properties of metal halide perovskite semiconductors, which are promising materials for high-efficiency, large-area thin-film solar cells, with the aim of understanding high-quality crystal growth and power generation mechanisms.

Preparation of Metal Halide Perovskite and Heterostructured Thin Films by Multi-source Co-Deposition

Study of photophysical properties of metal halide perovskite mixed crystals

Solar cells based on metal halide perovskite thin films

Nonlinear optical effects and quantum mechanical photocurrent in perovskite ferroelectric semiconductors

Terahertz wave generation from organic ferroelectrics and ferroelectric domain visualization

These are the main themes of our student-driven research.

[Ongoing Research Topics...]

Research on heteroepitaxial film fabrication

　We are studying heteroepitaxial thin films of halogenated perovskite thin films deposited on single crystals, which are expected to be used for light emitting and light receiving devices.

T. Matsushita, S. Takashima, Y. Nakamura, and T. Kondo, “Fabrication of CH₃NH₃PbI₃/CH₃NH₃PbCl₃ Heterostructure using Vacuum Evaporation,” 2018 International Conference on Solid State Devices and Materials (SSDM2018), September 9–13, 2018, The University of Tokyo, Tokyo,Japan (PS-6-11, Poster). etc.

Study of all-inorganic perovskite semiconductor thin film fabrication

　We are conducting research on the fabrication of high-quality thin films of all-inorganic halogenated perovskite CsSnBr₃ films, which are expected to have long-time stability and high environmental compatibility, by vacuum co-evaporation.

Z. Liu, H. Jung, M. Sotome, and T. Kondo, "Substrate temperature dependence of vapor phase deposition of all-inorganic lead-free CsSnBr₃ perovskite thin films." Japanese Journal of Applied Physics, 63, 01SP23 (2024). DOI: 10.35848/1347-4065/ad1196

Study of all-inorganic perovskite mixed crystal thin film fabrication

We are studying the fabrication of high-quality thin films of Zn-doped all-inorganic halide perovskite CsSnBr₃ films, which are expected to have long-time stability and high environmental compatibility, by vacuum co-evaporation and their application to solar cells.

H. Jung, Z. Liu, M. Sotome, and T. Kondo, "Vapor phase deposition of lead-free halide perovskite alloy CsSn_1-xZn_xBr₃." Japanese Journal of Applied Physics, 63, 01SP24 (2024). DOI: 10.35848/1347-4065/acfdb3

Perovskite semiconductor double heterostructure thin film films

We are conducting research to realize thin films with a tabular heterostructure, which is expected to be applied to light-emitting devices.

Shohei Toyota et al., "Fabrication of CsPbBr₃/CsSnBr₃/CsPbBr₃ double heterostructure by vacuum co-deposition",. , The 83th JSAP Spring Meeting, 24p-22C-9 (2024).

T. Matsushita, S. Takashima, Y. Nakamura, and T. Kondo, “Fabrication of CH₃NH₃PbI₃/CH₃NH₃PbCl₃ Heterostructure using Vacuum Evaporation,” 2018 International Conference on Solid State Devices and Materials (SSDM2018), September 9–13, 2018, The University of Tokyo, Tokyo,Japan (PS-6-11, Poster). etc.

Terahertz wave generation from organic ferroelectrics and ferroelectric domain visualization

We are studying terahertz wave generation by femtosecond laser irradiation and ferroelectric domain visualization using it in organic ferroelectrics, which are expected to be applied to next-generation electronics and photonics devices.

M. Sotome et al., "Three-dimensional visualization of the domain structure of molecular ferroelectrics [Hdabco][ReO₄] by terahertz electromagnetic wave generation", The 84th JSAP Autumn Meeting, 20a-B203-6 (2023).

[History]

Study of spoontaneous hybridization and photoinduced spinodal decomposition

We found that sequential stacking of lead halide perovskite polycrystalline thin films of CH₃NH₃PbI₃ (iodine-based) and CH₃NH₃PbBr₃ (bromine-based) spontaneously hybridizes, while photo-induced spinodal decomposition occurs, separating the two compositions upon light absorption.

Y. Nakamura, N. Shibayama, A. Hori, T. Matsushita, H. Segawa, and T. Kondo, “Crystal systems and lattice parameters of CH₃NH₃Pb(I_1-xBr_x)₃ determined using single crystals: Validity of Vegard’s law,” Inorg. Chem. 59, 6709–6716 (2020). DOI: 10.1021/acs.inorgchem.9b03421　 etc..

Sublattice-exchanged GaAs superlattice growth and wavelength conversion devices

　 We have researched the high-performance wavelength conversion devices that are expected to be applied to large-capacity optical communications and spectroscopy.

J. Ota, W. Narita, I. Ohta, T. Matsushita, and T. Kondo: “Fabrication of Periodically-Inverted AlGaAs Waveguides for Quasi-Phase-Matched Wavelength Conversion at 1.55 µm,” Jpn. J. Appl. Phys. 48, 04C110-1–4 (2009). DOI: 10.1143/JJAP.48.04C110. etc.

Waveguide type pseudo-phase matching wavelength conversion element

We researched the compound semiconductor crystal growth technology for wavelength conversion devices. Since compound semiconductors have extremely large nonlinear optical constants, they are excellent as wavelength conversion materials. We have independently developed and researched sub-lattice exchange epitaxy that controls the orientation of compound semiconductor crystals at the atomic level.

R. Narasaki, T. Matsushita, and T. Kondo, “Corrugation reduction in periodically inverted GaAs by molecular beam epitaxy growth using arsenic dimers,” Appl. Phys. Express 8, 025601-1–4 (2015). DOI: 10.7567/APEX.8.025601.　 etc.

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