In-situ micro-Raman study of SnSe single crystals under atmosphere: Effect of laser power and temperature

Single crystal of tin selenide (SnSe) was studied by micro-Raman spectroscopy under atmosphere conditions. The effect of varying the incident laser power on the sample up to 2 mW was analyzed. The Raman spectra showed that the number of all vibrational modes have not decreased or increased, but all peaks red-shifted and softened obviously as the laser power increased to the threshold value. The temperature-dependent micro-Raman study of the single crystal was carried out for illustrating thermal effect due to the high incident laser power. A new SnSe₂ phase appeared at high temperature without vacuum and become the dominant phase at the surface of the crystal gradually because of oxidation. Detecting few amounts of SnSe₂ crystals on the surface of single crystal shows the high sensitivity of Raman spectroscopy. High resolution transmission electron microscopy (HRTEM) was also used to confirm that the newly generated SnSe₂ phase is precipitated by SnSe under high temperature oxidation conditions. To study the Raman spectra of low thermal conductivity materials under high temperature and non-vacuum conditions, lower incident laser power should be used to avoid the influence of additional thermal effects.