Effects of substitution, pressure, and temperature on the phonon mode in layered-rocksalt-type Li(1-x)/2Ga(1-x)/2ZnxO (x=0.036-0.515) alloys

摘要

ZnO-based semiconductor alloys, Li(1-x)/2Ga(1-x)/2ZnxO (x = 0.036-0.515) with a layered-rocksalt-type structure, have been prepared under high pressure. The composition, pressure, and temperature dependence of phonons have been studied by Raman spectroscopy. We observe two disorder-activated Raman (DAR) modes when the Zn composition x increases: a broad Raman peak at ca. 400 cm(-1) and a left-shoulder peak at ca. 530 cm(-1) on the low-frequency side of A(1g) mode at ca. 580 cm(-1), which can be explained by reference to the phonon density of states for rocksalt-type ZnO. With the increase of the pressure and temperature, the left-shoulder DAR mode induced by substitution does not change at the same pace with the A1g mode at Brillouin-zone center. We find that ion substitution can be seen as a kind of chemical pressure, and the chemical pressure caused by internal substitution and the physical pressure caused by external compression have equivalent effects on the shortening of correlation length, the distortion of crystal lattice, and the change of atomic occupation. (C) 2015 AIP Publishing LLC.