Structural stability and Raman scattering of ZnSe nanoribbons under high pressure

Abstract The high-pressure in situ angular dispersive x-ray diffraction (ADXD) study on the zinc blende (ZB) type ZnSe nanoribbons were implemented using image-plate technique and diamond-anvil cell up to about 32 GPa. The pressure-induced structural transition from the ZB to a rocksalt (RS) type phase occurs at about 12.6 GPa, and the relative volume reduction at the transition point is close to 13%. Moreover, the variation in the relative volume with pressure seems discontinuous at about 5.5 GPa, which indicates an unidentified transition. The bulk modulus B 0 for the ZB and RS phases were determined through fitting the relative volume–pressure experimental data by Birch–Murnaghan equation of states. High-pressure Raman scattering experiments revealed that the transverse optical (TO) phonon mode splits into two peaks at about 5.5 GPa, which is compatible with the result of ADXD. The disappearance of the longitudinal optical peak above 13 GPa is due to the semiconductor–metal transition. Surprisingly, all Raman scattering peaks begin to become broad from the lower pressure (5–6 GPa) relative to the bulk ZnSe (normally ∼11 GPa), and the corresponding TO phonons become invisible beyond 14.7 GPa. Using the values of the bulk modulus from ADXD experiments, the corresponding mode Gruneisen parameters can be obtained for the ZB phase.