Lattice vibration of layered GaTe single crystals

The effect of interlayer interaction on in-layer structure of laminar GaTe crystals was studied according to the lattice vibration using micro-Raman analysis. The results were also confirmed by the first principle calculations. Accordingly, the relationship between lattice vibration and crystal structure was established. Ten peaks were observed in the micro-Raman spectra from 100 cm⁻¹ to 300 cm⁻¹. Eight of them fit Raman-active vibration modes and the corresponding displacement vectors were calculated, which proved that the two modes situated at 128.7 cm⁻¹ and 145.7 cm⁻¹ were related to the lattice vibration of GaTe, instead of impurities or defects. Davydov splitting in GaTe was identified and confirmed by the existence of the other two modes, conjugate modes, at 110.7 cm⁻¹ (∆ω = 33.1 cm⁻¹) and 172.5 cm⁻¹ (∆ω = 49.5 cm⁻¹), indicates that the weak interlayer coupling has a significant effect on lattice vibrations in the two-layer monoclinic unit cell. Our results further proved the existence of two layers in each GaTe unit cell.