Electrodeposition and Characterization of p-type Sb_xTe_y Thermoelectric Thin Films

Abstract

The electro-deposition of compound semiconductors has been attracting more attention because of its ability to rapidly deposit nanostructured materials and thin films with controlled morphology, dimensions, and crystallinity in a costeffective manner (1). In particular, low band-gap <TEX>$A_2B_3$</TEX>-type chalcogenides, such as <TEX>$Sb_2Te_3$</TEX> and <TEX>$Bi_2Te_3$</TEX>, have been extensively studied because of their potential applications in thermoelectric power generator and cooler and phase change memory. Thermoelectric <TEX>$Sb_xTe_y$</TEX> films were potentiostatically electrodeposited in aqueous nitric acid electrolyte solutions containing different ratios of <TEX>$TeO_2$</TEX> to <TEX>$Sb_2O_3$</TEX>. The stoichiometric <TEX>$Sb_xTe_y$</TEX> films were obtained at an applied voltage of -0.15V vs. SCE using a solution consisting of 2.4 mM <TEX>$TeO_2$</TEX>, 0.8 mM <TEX>$Sb_2O_3$</TEX>, 33 mM tartaric acid, and 1M <TEX>$HNO_3$</TEX>. The stoichiometric <TEX>$Sb_xTe_y$</TEX> films had the rhombohedral structure with a preferred orientation along the [015] direction. The films featured hole concentration and mobility of <TEX>$5.8{\times}10^{18}/cm^3$</TEX> and <TEX>$54.8\;cm^2/V{\cdot}s$</TEX>, respectively. More negative applied potential yielded more Sb content in the deposited <TEX>$Sb_xTe_y$</TEX> films. In addition, the hole concentration and mobility decreased with more negative deposition potential and finally showed insulating property, possibly due to more defect formation. The Seebeck coefficient of as-deposited <TEX>$Sb_2Te_3$</TEX> thin film deposited at -0.15V vs. SCE at room temperature was approximately 118 <TEX>${\mu}V/K$</TEX> at room temperature, which is similar to bulk counterparts.