ZnGeP2晶体中的晶格振动模拟与光谱分析

ZnGeP₂晶体在9~10 μm的光学吸收限制了其在中远红外波段的应用,该波段吸收与其晶格振动有关。本文通过理论计算与实验相结合的方法,解释了晶体红外截止边和9 μm附近吸收峰的物理机制。通过布里奇曼法生长出ZnGeP₂单晶,并测试生长得到的ZnGeP₂晶体的变温拉曼光谱和变压拉曼光谱,基于第一性原理方法计算了ZnGeP₂布里渊区中心的振动频率,并计算了不同压力下晶体的晶格常数和拉曼位移峰的位置。实验结果与理论计算结果表明:温度升高使得其振动模发生红移,且振动模强度减弱,半峰全宽变大,而压力增大则会引起ZnGeP₂晶体振动模发生蓝移,振动模强度减弱,半峰全宽变大。

Simulation of Lattice Vibration in ZnGeP2 Crystal and Its Spectral Analysis

The optical absorption at 9 μm to 10 μm related to lattice vibration in ZnGeP₂ crystal limited its application in the mid- and far-infrared range. To explain the physical mechanism of the infrared cut-off edge and the absorption peak near 9 μm in ZnGeP₂, a method combining theoretical calculations and experiments was used. Thus, the ZnGeP₂ single crystal was grown by the Bridgman method, and the temperature-dominated and pressure-dominated Raman spectrum of the grown ZnGeP₂ crystal were tested. In addition, the vibration frequency of ZnGeP₂ in the center of the Brillouin zone, the crystal lattice constant and Raman shift peak under different pressures were calculated based on the first-principles method. Experimental and theoretically calculated results reveal that the frequency of the vibration red shifts with temperature increasing, simultaneously, decrease of intensity and wider half-peak width of the vibration are observed. Besides, the frequency of the vibration blue shifts with pressure increasing, simulatenously, decreases of intensity and wider half-peak width of the vibration are observed.