Grant-in-Aid for General Scientific Research (B)
|Allocation Type||Single-year Grants|
|Research Institution||The University of Tokyo|
ITO Ryoichi UNIV. OF TOKYO, FAC. OF ENGINEERING, PROFESSOR, 工学部, 教授 (40133102)
KONDO Takashi UNIV. OF TOKYO, FAC. OF ENGINEERING, RESEARCH ASSOCIATE, 工学部, 助手 (60205557)
OGASAWARA Nagaatsu UNIV. OF ELETRO-COMMUNICATIONS, FAC. OF ENGINEERING, ASS. PROFESSOR, 電気通信学部, 助教授 (90134486)
GONOKAMI Makoto UNIV. OF TOKYO, FAC. OF ENGINEERING, ASS. PROFESSOR, 工学部, 助教授 (70161809)
ONABE Kentaro UNIV. OF TOKYO, FAC. OF ENGINEERING, ASS. PROFESSOR, 工学部, 助教授 (50204227)
HANAMURA Eiichi UNIV. OF TOKYO, FAC. OF ENGINEERING, PROFESSOR, 工学部, 教授 (70013472)
|Project Period (FY)
1990 – 1991
Completed(Fiscal Year 1991)
|Budget Amount *help
¥5,700,000 (Direct Cost : ¥5,700,000)
Fiscal Year 1991 : ¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1990 : ¥3,500,000 (Direct Cost : ¥3,500,000)
|Keywords||quantum-well / layered material / low-dimensional material / perovskite / nonlinear optics / structural phase transition / exciton / ペロブスカイト型構造 / 室温励起子|
Properties of new layered perovskite materials, especially (C_<10>H_<21>NH_3)_2PbI_4 (abbreviated to C_<10>PbI_4) and related compounds, have been studied with emphasis placed on their optical properties. Some very interesting phenomena, which are believed to stem from the two-dimensional character of these materials, have been found, including the determination of the third-order nonlinear optical coefficient of C_<10>PbI_4 ; its peak value is estimated to be 0.7 X10^<-9>esu, which is as large as those of polydiacetylenes, well-known one-dimensional materials.
1. The crystal structure of C_<10>PbI_4 has been analyzed over a temperature range of 70ﾟC to -40ﾟC. Three structural phase transitions have been identified.
2. Optical properties, including absorption, reflection and luminescence spectra, of C_<10>PbI_4 have been studied in detail. The lowest-energy transition due to excitons shifts appreciably around 0ﾟC upon a phase transition.
3. The electro-absorption studies of C_<10>PbI_4 in
dicate a very strong two-dimensional character of the exciton, its binding energy being possibly as large as 590 meV.
4. Magneto-absorption spectra of C_<10>PbI_4 have been taken up to magnetic fields as high as 40 T. Diamagnetic shifts in the Faraday configuration yield an exciton binding energy of 360 meV. No peak shifts are observed in the Voigt configuration, probably owing to the two-dimensional confinement of the exciton.
5. Optical third-harmonic generation has been observed on C_<10>PbI_4 over the wavelength range 1.77-1.50mum. The largest value of chi^<(3)> is 0.7X10^<-9>esu for lambda= 1.53mum, which is three-photon resonant with the exciton transition.
6. Photo-conductivity of C_<10>PbI_4 has been observed. Carriers generated by exciton dissociation are believed to be transported within the [PbI_4] layers. This is probably the first observation of carrier transport in strictly two-dimensional structures.
7. Optical properties of C_<10>PbI_4 are being studied. Since this compound does not undergo phase transitions below room temperature, it reveals exciton features at low temperatures which are mudi better resolved than C_<10>PbI_4.
From the above results, it has become established that C_<10>PbI_4, a perovskite material with a natural quantum-well structure, is an ideally two-dimensional substance. Very strong anisotropies due to this two-dimensional structure have been observed in its electrical and optical properties. Plans are under way to further study this and other related compounds, focusing on their nonlinear optics and exciton dynamics. Less