Raman Spectroscopy and In Situ XRD Probing of the Thermal Decomposition of Sb2Se3 Thin Films

Sb2Se3 thin films have received increasing interest for their applications in optoelectronics. However, technological intervention demands a material-specific understanding of the reactivity to different environments. Both thermal annealing and laser irradiation carried out in an ambient atmosphere are expected to induce changes in the pristine crystallographic phase of Sb2Se3, causing the creation of additional secondary phases. Here, we investigate by means of Raman spectroscopy the effect of thermal annealing and laser irradiation at different fluencies on the structural and vibrational properties of Sb2Se3 thin films. The vacuum-annealed Sb2Se3 thin films at 290 °C and subjected to laser excitation power above 2 mW exhibit a secondary phase, revealing the occurrence of selenization. Further, in situ X-ray diffraction over a broad range of annealing temperatures in N2 and ambient atmospheres was employed to study the structural properties of the Sb2Se3 thin films. In situ XRD performed in a N2 atmosphere does not show the formation of the Sb2O3 cubic phase upon annealing until 500 °C. Conversely, a thermally activated systematic crystallization was observed upon annealing in an ambient atmosphere with the formation of the Sb2O3 phase in the temperature range between 280 and 420 °C, until the complete decomposition of the material at 500 °C. Further, the orientation of vertically stacked (hk1) planes remains unchanged under a N2 atmosphere, while horizontally stacked (hk0) planes dominate the (hk1) planes under ambient atmospheres.