| Budget Amount *help |
¥5,900,000 (Direct Cost: ¥5,900,000)
Fiscal Year 2000: ¥5,900,000 (Direct Cost: ¥5,900,000)
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| Research Abstract |
We have fabricated assembled semiconductor nanocrystals by ion-implantation, colloid, and vacuum-deposition techniques and studied their optical properties. The a-Si/SiO_2 multilayer structures on (001) Si substrates were formed by an electron beam deposition technique. The size dependence of the luminescence spectrum and lifetime showed that high-quality two-dimensional a-Si layers were formed between SiO_2 layers. After thermal annealing of a-Si/SiO_2 multilayers, arranged Si nanocrystals were formed between SiO_2 layers and the size of Si nanocrystals were determined by the thickness of the a-Si layer. The Ge nanocrystals samples were synthesized by multi-energy or low-energy ion-implantation techniques. This multi-energy ion implantation gave a uniform Ge concentration profile in SiO_2 glasses. The transmission electron microscopy (TEM) observations showed that the size fluctuation of Ge nanocrystals was very small. In addition, the low-energy ion implantation produced Ge nanocrystal in the very narrow region in SiO_2 matrices. The TEM observation showed that the Ge nanocrystals were lined up near the surface. The size fluctuation of nanocrystals in this work is much smaller than that of prepared by conventional ion-implantation and rf co-sputtering techniques. Moreover, we have developed new fabrication methods of compound semiconductor nanocrystals in SiO_2 or Al_2O_3 films by sequential ion implantation. ZnS and CdS nanocrystals in Al_2O_3 matrices were faced and aligned with the Al_2O_3 lattice. In GaAs, ZnS, and CdS nanocrystals, efficient photoluminescence due to free excitons appeared near the absorption edge. Spectroscopic analysis showed that high-quality compound semiconductor nanocrystals were formed by sequential ion implantation techniques. It is demonstrated that ion implantation synthesis is one of the most versatile methods for the fabrication of assembled semiconductor nanocrystals.
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