用高压显微光谱系统测量流体静压力对非晶态As_2S_3光学吸收边的影响

MEASUREMENT OF HYDROSTATIC PRESSURE EFFECT ON OPTICAL ABSORPTION EDGE OF AMORPHOUS As_2S_3 USING HIGH-PRESSURE MICROSPECTROSCOPIC SYSTEM

用金刚石对顶砧高压显微光谱系统在0—66 kbar的流体静压力范围内测量了a-As_2S_3的光学吸收达随压力的移动特性。发现a-As_2S_3的光学吸收边随压力的增加而迅速红移。在计算机上用最小二乘法对实验点进行了拟合,结果得出吸收边和压力之间的关系为:E_g(P)=E_g(0)-1.31×10^(-3)P-3.91×10^(-4)P^2+4.04×10^(-6)P^3值得注意的是|dE_g/dP|和压力之间的关系经历了一个先是增大,然后再减小以至于趋于饱和的过程。这和Weinstein等人先前的实验结果是有所不同的。

Shift of optical absorption edge of amorphous As2S3 with increasing hydrostatic pressures up to 66 kbar has been quantitatively measured by means of high-pressure mic-rospectroscopic system in conjunction with gasketed diamond anvil cell under room-temperature. The method of ruby fluorescence shift technique was adopted for pressure calibration. Amorphous As2S3 thin film samples a few micrometers in thickness were prepared by vacuum evaporation. Under our experimental conditions, neither the light of 4416 A He-Cd laser used for excitation of the ruby gauge, nor that of the Br-W lamp for measurement of light transmission, showed any detactable influence on the optical properties of the sample. Rapid red-shift of optical absorption edge with increasing pressure was observed, Eg dropped from 2.58 eV to 1.95 eV between 1 bar and 66 kbar. An empirical formula of experimental data was obtained. The relationship of absorption edge and pressure is as follows:Eg (P) = Eg(0)- 1.31 × 10-3P- 3.91 × 10-4P2 + 4.04 × 10-6P3.It is noteworthy that the dependence of |dEg/dP| upon pressure was increasing at first and then decreasing gradually to saturation at high pressure. This result shows something different from privious one obtained by Weinstein et al. The origin of the difference was discussed.