| Budget Amount *help |
¥7,700,000 (Direct Cost: ¥7,700,000)
Fiscal Year 1997: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1996: ¥6,300,000 (Direct Cost: ¥6,300,000)
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| Research Abstract |
Luminescence hole-burning phenomena were observed in CuCl quantum dots embedded in a NaCl crystal.As a result of the selective excitation, a resonantly burned hole and monreover its sidebands appear in the luminescence spectrum. The Stokes shift of the sidebands is explained by the quantum size effect of the negatively charged excition X^- and the positively charged exciton X_2^+. New exciton complexes, X^- and X_2^+, confined in quantum dots were first observed by the luminescence hole burning.
A persistent spectral-hole-burning (PSHB) phenomenon was successfully applied to the precise site-selective spectroscopy of CuCl quantum dots embedded in NaCl crystals. In the PSHB spectra of CuCl quantum dots, a resonantly burned hole and lower-energy satellite holes were observed. Energy relation between the resonantly burned hole and each satellite hole is well explained by the simple concept of a particle in a quantum cube with an infinitely high potential barrier.
Formation efficiencies of the persistent hole in cuprous halides quantum dots, CuCl, CuBr and CuI quantum dots embedded in glass or alkali halide crystals, were measured. The highest quantum efficiency of 0.009 was obtained at 2 K for CuCl quantum dots in glass. This high sensitivity shows the PSHB phenomenon in semiconductor quantum dots is very hopeful for the multiple optical memory device.
At 2 K,the hole spectrum in CuCl quantum dots consists of a zero-phonon line (linewidth=0.14meV) and its acoustic phonon wing, and they are well separated from each other. With increasing the temperature T,the zero-phonon hole and its phonon sideband are merged to each other and finally the hole spectrum shows broadening. Contrary to the usual exciton broadening of the linear temperature dependence, the broadening is proportional to 1/ [exp (delta/kT) -1] at low temperature, where delta is the confined acoustic phononenergy in quantum dots.
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