Enhanced thermoelectric properties of SnSe thin films grown by pulsed laser glancing-angle deposition

摘要

SnSe single crystals have been demonstrated to possess excellent thermoelectric properties. In this work, we demonstrate a grain size control method in growing nanocrystalline SnSe thin films through a glancing angle pulsed-laser deposition approach. Structural characterization reveals that the SnSe film deposited at a normal angle has a preferred orientation alongaaxis, while by contrast, the SnSe film deposited at an 80° glancing angle develops a nanopillar structure with the growth direction towards the incident atomic flux. The glancing angle deposition greatly reduces the grain size of the thin film due to a shadowing effect to the adatoms, resulting in significantly increased power factor for more than 100%. The maximum Seebeck coefficient and power factor are 498.5μV/Kand 18.5μWcm?1K?2, respectively. The enhancement of thermoelectric property can be attributed to the potential barrier scattering at grain boundaries owing to the reduced grain size and increased grain boundaries in the film. Given this enhanced power factor, and considering the fact that the nanopillar structure should have much lower thermal conductivity than a plain film, thezTvalue of such made SnSe film could be significantly larger than the corresponding single crystal film, making it a good candidate for thin film-based thermoelectric device.Graphical abstractDisplay OmittedHighlights?Orthorhombic SnSe films are deposited using pulsed laser deposition.?Optimized deposition temperature of SnSe film is 330?°C.?Nanopillar structure observed on sample deposited at a glancing angle.?TE performance of film deposited at a glancing angle is greatly enhanced.?Enhancement can be attributed to potential barrier scattering at grain boundaries.