Realizing the giant seebeck coefficient and electrical conductivity in SnTe thin films by grain engineering

In this work, we have modulated the film growth parameter (post growth annealing) of SnTe-based thin films to enhance the charge carrier transport by controlling the morphology and microstructure. The samples under investigation were prepared by a vacuum tube furnace on a glass substrate using following growth conditions; growth temperature 700 degrees C, pressure in the tube 180 mTorr, source to substrate distance 7 cm. Grain engineering was performed by annealing the samples at different temperatures (200-500 degrees C) which was used as a powerful tool to enhance the mobility of charge carriers (7-13 cm2/V-Sec). SEM images demonstrated that a representative sample annealed at 300 degrees C has a layered structure, therefore the carriers in this sample possessed the highest value of mobility. This encouraging value of carrier mobility resulted in the enhancement of the Seebeck coefficient (7600 mu V/K) and electrical conductivity (5S/cm) simultaneously. XRD and Raman spectroscopy measurements were also performed to crystal structure and vibrational modes of annealed SnTe thin films. In conclusion, it is reported that the annealing temperature of 300 degrees C is supposed to be the optimal value for required grain engineering in order to realize the highest value of the Seebeck coefficient and electrical conductivity.