Thermoelectric properties of Bi2Te3/Sb2Te3 superlattice structure

摘要

Recently, it has been proposed that the use of superlattice structure is effective for reduction of lattice thermal conductivity in the direction perpendicular to superlattice interfaces which can lead to improvement of figure of merit. In thiswork, we have evaluated the thermal conductivity of Bi{sub}2Te{sub}3 and Sb{sub}2Te{sub}3 superlattice structure films. Pulsed laser deposition (PLD) has been employed as film formation method because it can easily make superlattice structure by ablatingtargets alternately. Bi2Te3 and Sb2Te3 films were grown respectively and effects of substrate temperature and laser power density on crystallinity, morphology and composition were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM) and energy dispersive X-ray analysis (EDX). Bi2Te3/Sb2Te3 superlattice structure films were grown with superlatticeperiods of lOnm, 2Onm and 8Onm. Thermal conductivities were measured in the direction perpendicular to superlattice interfaces by anovel method specially developed by our group. We compared the thermal conductivities of Bi{sub}2Te{sub}3/Sb{sub}2Te{sub}3 superlattice structure films with that of Bi{sub}2Te{sub}3 single film. The results indicates that the involvement of superlatticestructure into thermoelectric film is effective for the reduction of thermal conductivity and moreover, thermal conductivity becomes smaller as superlattice-period becomes shorter as predicted.