KPFM based investigation on the nature of Sb2Te3:MoS2 and Bi2Te3:MoS2 2D interfaces and its effect on the electrical and thermoelectric properties

Abstract

In this study, the effect of incorporation of 2D nanoflakes on an n type and a p type thermoelectric matrixes, Bi2Te3 and Sb2Te3, respectively, has been studied. MoS2 has been used to prepare nanocomposite bulk samples having n-n or n-p 2D interfaces. Kelvin probe force microscopy based measurements were used to characterize nanocomposite samples which revealed a difference in potentials barrier at the 2D interface for Bi2Te3:MoS2 and Sb2Te3:MoS2 samples, respectively. The electrical conductivity of Bi2Te3:MoS2 was observed to be lower as compared to the pristine Bi2Te3 due to increased electron scattering at 2D interfaces, whereas in the case of Sb2Te3:MoS2, the incorporation of MoS2 led to the increase in the value of electrical conductivity due to higher carrier mobility. In Bi2Te3:MoS2, a large decrease in thermal conductivity due to reduced electronic contribution is observed in contrast to no change in the case of the Sb2Te3:MoS2 nanocomposite sample. The Seebeck coefficient is observed to increase in both the types of nanocomposite samples but owing to different mechanisms. The presence of potential barrier for electrons restricts the flow of majority carriers in the Bi2Te3:MoS2 nanocomposite, whereas in the case of Sb2Te3:MoS2 nanocomposite samples, the increased potential barrier helps in assisting the flow of holes, thereby increasing the mobility of carriers in the case of Sb2Te3:MoS2.