Electrical and thermal transport properties of electrically stressed Bi–Sb–Te nanocrystalline thin films

• Published in: Thin solid films 2011-04, Vol.519 (13), p.4394-4399
• Main Authors: Liao, Chien-Neng, Su, Xiao-Wei, Liou, Kuen-Ming, Chu, Hsu-Shen
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deposition by sputtering; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport phenomena in thin films and low-dimensional structures; Exact sciences and technology; Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects); Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Nanocrystalline film; Nanoscale materials and structures: fabrication and characterization; Other topics in nanoscale materials and structures; Physical properties of thin films, nonelectronic; Physics; Sputtering; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thermal stability; thermal effects; Thermoelectric properties
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2011.02.066

Nanoscale size effect is beneficial for enhancing thermoelectric figure-of-merit of Bi–Sb–Te compounds due to the decrease of thermal conductivity. Bi–Sb–Te nanocrystalline thin films prepared by sputtering at room temperature, in general, require a post-deposition treatment to improve their electrical transport properties by eliminating residual crystal defects. In this study we present an electric current stressing treatment to effectively eliminate crystal defects in sputtered Bi–Sb–Te films at low temperature. By maintaining a low thermal conductivity of 0.6–0.7 W/mK, the electrically stressed Bi–Sb–Te nanocrystalline films possess highly enhanced Hall mobility and moderately reduced carrier concentration as compared to the films thermally treated at the same temperature. Carrier concentration, mobility and Seebeck measurement results suggest that the change of electrical transport properties involves the elimination of Sb Te antisite defects as supported by the observation of some Sb-rich precipitates in the thermally/electrically treated Bi–Sb–Te films. Besides, crystal defects are also suggested to be preferentially removed in the (00 l)-oriented grains due to anisotropic diffusion and electrical transport properties in the electrically stressed Bi–Sb–Te films.