Growth and thermal stability studies of layered GaTe single crystals in inert atmospheres

Abstract

In this study, we investigated the thermal stability properties in inert atmospheres of GaTe single crystals fabricated by a temperature gradient technique. The obtained crystals possess a monoclinic layered structure with high crystalline quality. To explore the thermal stability of GaTe, the differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed up to 1173 K in N2 and Ar atmospheres. GaTe crystals are thermally stable up to 700 K in Ar and stable up to 935 K in N2 due to the protective role of the physically adsorbed N2 molecules on GaTe surface. Annealing effect on the structural and optical properties of GaTe were examined after thermal treatment in N2 atmosphere at different temperatures; 573, 673, 773, and 873 K. Three prominent Raman modes at 97 cm1 (Ag), 145 cm1 (Ag), and 158 cm1 (Bg) corresponding to the monoclinic GaTe phase almost remained, suggesting no structural damage at elevated temperatures. Especially, the photoluminescence (PL) intensity is improved as the annealing temperature increases and reaches a maximum at 673 K owing to the enhancement in the GaTe crystallinity. Above 873 K, we observed a significant reduction in the PL intensity, which is attributed to the vacancies induced by tellurium evaporation.