| Co-Investigator(Kenkyū-buntansha) |
YAMAGUCHI Hiroyuki Gunma University, Department of Electronic Engineering, Research Associate, 工学部, 助手 (80261866)
MINAMI Hidetoshi University of Tsukuba, Institute of Applied Physics, Lectuer, 物理工学系, 講師 (00190702)
ITOH Fumitake Gunma University, Department of Electronic Engineering, Professor, 工学部, 教授 (60005907)
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| Research Abstract |
1.Refining by Floating Zone Technique and Evaluation of Oxide Materials ; High-purity specimens of Cu_2O and CuO have been studied as the basic substances towards the Cu-O network in the Cuprate superconductive Oxides by spectrochemical analysis, X-ray diffraction, optical absorption, photoluminescence, and Raman scattering. These results revealed remakably new results both on Cu_2O and especially on CuO.
2.A Trial Study of Phase Transition in Insulating Oxides by using the Anomalous Compton Scattering ; We have tried to pursue a potential existence of phase transitions of the valence electronic system in Cu_2O via studying the temperature dependence (T=15-300K) of the momentum distribution and spin polarization in the anomalous Compton scattering. Unfortunately, clear results have not been obtained because of lack of machine time available in the Synchrotron Oribit Radiation (SOR) Facilities in the High Energy Physics Laboratory (KEK).
3.Studies of the Correlation between Phase Transiti
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ons and Occurrences of Anomalies in Photoconductivity ; With a wider view than ever, we extended our studies on the correlation between phase transitions and occurrences of anomalies in photoconductivity by studying the temperature dependence of pulsed photoconductivity in various substance, especially unexpectedly emerging photosignals with decreasing temperature in details, at wider electric and magnetic fields, wavelength and intensity of photoexcitation. Particularly, besides Cu_2O,we have extended studies to cover CuO,Sm_2CuO_4, etc.and obtained results remarkably similar to those in Cu_2O.We are approaching the Cu-O based superconductors by photodoping.
4.Nonlinear Photomagnetism-Optical-Microwave Cyclotrone Double Resonance ; We have investigated intensively the nonlinear optical-microwave double cyclotron resonance of Cu_2O due to polarons with excitons in details. Besides, on the problem of an existence of the mid-gap states in Cu_2O,we newly studied the temperature dependence of microwave photoconductivity signals between T=4.2K and 300K similar to pulsed photoconductivity signals in a view of dynamical aspects of photoresponses at 35GHz. We have observed a resonant enhancement of microwave photoconductivity at lambda=614nm and around T=60K.
5.Search for Superconductive-Conjugate Photoconductive Substance and Dynamics of Photoresponses ; We have examined the optical absorption, photoconductivity, photoluminescence of single or polycrystals and thin film of CuO,Sm_2CuO_4, etc.. and newly confirmed that CuO and Sm_2CuO_4 exhibit superconductive-conjugate photoconductivity. We have also studied the optical absorption of Ba_<1-x>K_xBiO_3 and light-irradiated effect on reduced Y-Ba_2-Cu_3-O_<7-delta>.
6.Basic Studies of Superconductive Optoelectronic Devices ; By adopting a combination of the Cu-O based high-Tc Superconductor pairs and the insulator Cu_2O of superconductive-conjugate photoconductivity, we have pursued a possibility to build a superconductive optoelectronic device and of their application. In a basic aspect, we discovered a resonant shift of temperature dependence of photoconductivity of Cu_2O at the gate region with the occurrence of superconductive transitions of the Y-Ba-Cu-O,La-Sr-Cu-O,or La-Ba-Cu-O at the source and drain regions. In an aspect for applications, we confirmed a possibility of basic operation as a photo-transistor including three terminal FET-like arrangements. These results reveal a possibility to develop an integrated array of photoelectric devices at high density and high speed operations. Less
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