Effect of Initial Bulk Material Composition on Thermoelectric Properties of Bi^sub 2^Te^sub 3^ Thin Films

Issue Title: 2012 International Conference on Thermoelectrics. Guest Editors: Ryoji Funahashi, Donald Morelli, Lasse Rosendahl, and Jihui Yang V^sub 2^VI^sub 3^ compounds and solid solutions based on them are known to be the best low-temperature thermoelectric (TE) materials. The predicted possibility of enhancement of the TE figure of merit in two-dimensional (2D) structures has stimulated studies of the properties of these materials in the thin-film state. The goal of the present work is to study the dependences of the Seebeck coefficient S, electrical conductivity σ, Hall coefficient R ^sub H^, charge carrier mobility [mu] ^sub H^, and TE power factor P = S ^sup 2^ σ of Bi^sub 2^Te^sub 3^ thin films on the composition of the initial bulk material used for preparing them. Thin films with thickness d = 200 nm to 250 nm were grown by thermal evaporation in vacuum of stoichiometric Bi^sub 2^Te^sub 3^ crystals (60.0 at.% Te) and of crystals with 62.8 at.% Te onto glass substrates at temperatures T ^sub S^ of 320 K to 500 K. It was established that the conductivity type of the initial material is reproduced in films fairly well. For both materials, an increase in T ^sub S^ leads to an increase in the thin-film structural perfection, better correspondence between the film composition and that of the initial material, and increase in S, R ^sub H^, [mu] ^sub H^, σ, and P. The room-temperature maximum values of P for the films grown from crystals with 60.0 at.% and 62.8 at.% Te are P = 7.5 × 10^sup -4^ W/K^sup 2^ m and 35 × 10^sup -4^ W/K^sup 2^ m, respectively. Thus, by using Bi^sub 2^Te^sub 3^ crystals with different stoichiometry as initial materials, one can control the conductivity type and TE parameters of the films, applying a simple and low-cost method of thermal evaporation from a single source.[PUBLICATION ABSTRACT]