退火温度对a-Se0.70Ge0.15Sb0.15薄膜的结构和光学性质的影响

摘要

Thin films of amorphous bulk Se0.70 Ge0.15 Sb0.15 system are deposited on a quartz and glass substrates at 300K by the thermal evaporation technique. The amorphous films were annealed at 370 and 470K in vacuum ～ 10-4Pa for 1h. The as-deposited and annealed films were checked by X-ray diffraction. On annealing at 470K(in the same time and vacuum), the films revealed crystalline nature. The optical constants such as refractive index( n ), absorption coefficient (α) and extinction coefficient (k) were determined from the measured transmittance and reflectance at normal incidence of light in the wavelength range 300～2 500nm. It was found that both( n ) and (k) depend markedly on the temperature of heat treatment. The analysis of the optical data gave non-direct band gaps(Enong)of 1.715 + 0.021, 1,643 + 0.021 and 1.572 + 0.021eV for as-deposited, 370K and 470K annealed samples respectively. The annealing temperatures are decreased the band gap(Enong)and increasing the band-tail(Ee). This effect is interpreted in terms of the density of state model in amorphous solids proposed by Mott and Davis. The Wemple-DiD omenico single oscillator model parameterizes for as-deposited and annealed films are determined.%研究了退火温度对Se0.70Ge0.15Sb0.15薄膜的影响.通过热蒸发技术,在300K温度下将大块无定形Se0.70Ge0.15Sb0.1s沉积在石英和玻璃衬底上.研究发现,未经过退火处理的薄膜结构和在300K,1.33×10-5Pa下退火1小时后的薄膜结构都是无定形结构,而在同样气压470K温度下退火1小时的薄膜有结晶现象.通过在300 2 500nm范围内垂直入射光方向上透射率和反射率的测试,研究了薄膜的一些光学参数,如消光系数(k),折射系数(n)和吸收系数(a).研究发现,n和k同热处理温度有关.通过光学数据的分析,得到了不同条件下薄膜的间接带隙宽度(Enong),未经过热处理薄膜的Enong是1.715±0.021eV,300K下退火薄膜的Enong是1.643±0.021eV,470K下退火的Enong是1.527±0.021eV.退火温度降低了带隙宽度Enong,但增加了带尾eo这种效应可以根据Mott和Davis提出的多晶体系中态密度来解释.