Summary of Research Project Results Under the JSPS FY2000
"Research for the future Program"

1.Research Institution Ritsumeikan University
2.University-Industry Cooperative Research Committee 147th Committee on Amorphous and Nano-Crystalline Materials
3.Term of Project FY1996〜FY2000
4.Project Number 96R14701
5.Title of Project Physics of Nanocrystalline Semiconductors and their Application to New Functional Devices

6.Projetct Leader
Name Institution,Department Title of Position
Yoshihiro Hamakawa Ritsumeikan University Professor

7.Core Members

Names Institution,Department Title of Position
Hiroaki Okamoto Osaka University Professor
Masataka Hirose Hiroshima University Professor
Hideyuki Takakura Ritsumeikan University Professor

8.Cooperating Researchers

Names Institution,Department Title of Position
Fumiko Yonezawa Keio University Professor
Shoji Nitta Gifu University Professor
Seiichi Miyazaki Hiroshima University Associate Professor

9.Summary of Research Results

A series of investigations on physics of nano-crystalline semiconductors and their application to new functional devices have been made. Results are summarized as following:
1) On the fabrication technologies of nano-crystalline silicon, optimum deposition conditions for the best quality of the film are identified and their electrical and opto-electronic properties are characterized.
2) With the detailed parameter control in the initial deposition, homogeneous semispherical nc-Si dots were fabricated successfully. Result of PL spectra measurements are explained by the theory of quantum dot model.
3) Observed EL emission has two distinguished structures centered at 1.3eV and 1.6eV. In the higher energy side structure, one can see dark red visible light due to the broad band emission.
4) On the basis of these experimental results, an attempt has been made on the higher energy gap nanocrystal materials. We have succeeded a strong red light emission from nc-ZnS:Mn.
5) With the tight-binding-approximation, electronic band structure and the electronic density of state in nc-Si are calculated firstly. It has been shown that experimentally observed light emission could be explained by the deviation of the crystal symmetry including bond length and tilt angles in the system.
6) Utilizing the excellent photoconductive and electrical properties in the nc-Si, high efficiency low cost a-Si//nc-Si tandem type solar cells are proposed and both experimentally and theoretically verified.

10.Key Words

(1)nanocrystalline semiconductor、(2)amorphous silicon、(3)valency control
(4)band gap energy control、(5)self-assembling、(6)quantum dot
(7)thin film light emitting device、(8)tandem type solar cell、(9)OEIC


[Reference Articles]
Author Title of Article
J. Koga, K. Nishio, H. Ohtani, T. Yamaguchi, and F. Yonezawa Electronic Properties of Low Dimensional Si Nanostructure, I. Local Electronic Probabilities
Journal Volume Year Pages Concerned
J. Phys. Soc. Jpn. 69 2000 2188

Author Title of Article
S. Miyazaki, K. Shiba, N. Miyoshi, K. Etoh, A. Kohno and M. Hirose Luminescence Study of Self-Assembled Silicon Quantum Dots
Journal Volume Year Pages Concerned
Mat. Res. Soc. Symp. Proc. 536 1999 45-50

Author Title of Article
S. Nonomura, T. Gotoh, M. Nishio, T. Sakamoto, M. Kondo Photoinduced Expansion in Hydrogenated Amorphous Silicon
Journal Volume Year Pages Concerned
Mat. Res. Soc. Symp. Proc. 577 1999 337-345

Author Title of Article
T. Toyama, Y. Kotani, H. Okamoto, and H. Kida Light Emission from Nanocrystalline Si Thin-Film Light Emitting Diodes due to Tunneling Carrier Injection
Journal Volume Year Pages Concerned
Appl. Phys. Lett. 72 1999 1489-1491

Author Title of Article
Y. Hamakawa and H. Takakura Key issues for the efficiency improvement of silicon basis stacked solar cells
Journal Volume Year Pages Concerned
Conf. Record 28th IEEE PV Spec. Conf.   2000 766-771

[Reference Books]
Author Title of Book
Shoji Nitta et al. Sample Fabrication Technologies -Amorphous Materials-
Publisher Year Pages
Maruzen Pub. Co. 2000 302

Author Title of Book
Y. Hamkawa, H. Okamoto, H. Takakura et al. Solar PV Power Generation -Recent Technologies and Systems-
Publisher Year Pages
CMC 2000 318

Author Title of Book
H. Okamoto, H. Takakura et al. Fundamentals and Application of Thin Film Solar Cells
Publisher Year Pages
OHM-Sha Pub. Co. 2001 265