Hokkaido University · 재료과학
Keiji Tanaka 교수의 연구실은 셀레니드 및 텔루라이드 기반의 화학적·구조적 특성을 가진 채르코이드 유리의 광학적, 전자적 성질을 중심으로 연구를 진행하고 있습니다. 특히 광유도 유동성, 광팽창, 가역적 광어두움 현상 등 광자극에 의한 구조적 변화 메커니즘을 원자구조 및 전자구조적 관점에서 규명하고 있으며, 이는 나노리어조 및 광학 소자 응용에 기여합니다. 연구는 X선 회절, 광흡수 특성 분석 및 열역학적 모델링을 융합하여 진행됩니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
The composition dependence of the structural and electronic properties in chalcogenide glasses suggests that there exists a structural phase transition at the average coordination number of 2.67. Materials having smaller coordination numbers are characterized by molecular structures, and otherwise three-dimensional networks govern the properties. The result is discussed in light of topological and percolative arguments.
It was found that chalcogenide glasses can be shaped by stressing the glass under light illumination because light illumination enhances the fluidity of the glass. The mechanism of photoinduced fluidity was found to be photoelectronic, that is, athermal. The process can be applied to microfabrication of optical fibers and glassy films with a typical dimension of 10 to 100 micrometers.
Mechanisms of photoexpansion in chalcogenide glasses have been studied in three respects. A detailed x-ray investigation of ${\mathrm{As}}_{2}{\mathrm{S}}_{3}$ shows that the photoexpansion can be connected with asymmetric broadening of the first sharp diffraction peak. Comparison between radiation-induced volume changes and density ratios of glassy-to-crystalline forms in ${\mathrm{As}}_{2}{\mathrm{S}}_{3}$ and ${\mathrm{SiO}}_{2}$ implies that ${\mathrm{As}}_{2}{\mathrm{S}}_{3}$ can expand sin
Mechanisms of the reversible photodarkening phenomenon have been studied for amorphous S and Se. These materials exhibit smaller photodarkening effects when illuminated with sub-bandgap illumination at 80 K. A configurational model is proposed for interpreting the results, and parameters characterizing the model are estimated. This model is connected with a structural model which assumes photoinduced bond twisting. By using the modified valence-forcefield constants, it is shown that the structur
Shifts in the optical-absorption edges induced by band-gap illumination and annealing under pressure have been studied for ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$ and Se. Both materials, if annealed at 1 atm beforehand, undergo a decrease in the band-gap energy with illumination under pressure. This decrease is accompanied by a similar degree of densification as that induced by annealing. The ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$ specimen annealed under pressure at the glass-transition temperature
