RAMAN-SPECTROSCOPY STUDY OF ZNSE AND ZN0.84FE0.16SE AT HIGH-PRESSURES

The ZnSe powder and Zn0.84Fe0.16Se crystal were studied by Raman scatt ering spectroscopy at pressures up to 36.0 and 32.0 GPa, respectively. For ZnSe powder at 4.7 and 9.1 GPa, two phase transitions were observ ed. However, the resulted phases have not been identified yet. As the pressure was increased to 14.4 GPa, the LO phonon peak disappeared whi le the TO phonon peak was still visible until the metallization pressu re, 17.0 GPa was reached. In addition, three unidentified Raman peaks were still observable above the metallization pressure. For Zn0.84Fe0. 16Se crystal, the structure transition from possible zinc blende to so dium chloride phase (B-1) was identified by the disappearance of Fe lo cal mode and longitudinal optical (LO) phonon mode at 10.9 GPa. In add ition, an unidentified phase transition at 4.7 GPa was observed. The T O phonon and the split TO phonons were still observable at a pressure above the phase transition pressure up to 32.0 GPa. The existence of F e impurity in the ZnSe up to a concentration of 0.16 reduced the semic onductor-metal phase transition pressure to 10.9 GPa. According to the calculation of Gruneisen parameters, Zn0.84Fe0.16Se was found to have a higher ionicity than ZnSe. Reasons for the observation of Raman pea ks at a pressure above the metallization pressure are still unknown.