High Pressure Raman Study of Layered Semiconductor Tlgase₂

Raman spectroscopy measurements of a monoclinic layered semiconductor TlGaSe₂were performed in a pressure range up to 10.24 GPa. The pressure-induced first-order phase transition accompanied by reconstruction of the layer structure was observed at the pressure P ~ 0.9 GPa. The mode-Grüneisen parameters of intralayer bonds were calculated for TlGaSe₂. The contribution of thermal expansion to temperature changes of phonon frequencies was defined. The type of intralayer bonds and their pressure transformation were analyzed in layered TlGaSe₂. It was shown that the nature of intramolecular forces in molecular crystals and intralayer forces in layered GaS, GaSe and TlGaSe₂is similar