Nanoscale thermoelectric properties of Bi2Te3 - Graphene nanocomposites: Conducting atomic force, scanning thermal and kelvin probe microscopy studies

In the present study, the effect of the presence of monolayer graphene (G) on the nanoscale electrical and thermal conductivities of Bi2Te3 has been investigated. Atomic force and conducting atomic force microscopic studies show that G incorporation results in lower electrical conductivity at Bi2Te3: Graphene (Bi2Te3: G) interfaces. The Kelvin probe and scanning thermal images show that Bi2Te3 composites have different work function and thermal conductivity values compared to Bi2Te3 sample. The decrease in the value of thermal conductivity was further confirmed by measuring the thermoelectric properties of Bi2Te3 and its composites in the temperature range 300-480 K. The simultaneous increase in the value of power factor and decrease in the value of thermal conductivity of the Bi2Te3/G composite sample led to enhanced value of ZT - 0.92. This increase in the value of ZT is attributed to increased phonon scattering, and limited effect on the electron transport due to large interface area and 2D nature of G. The present study provides an insight into a new path for direct nanoscale measurements of topographical, electrical and thermally conducting characteristics of nanocomposite samples which is important for establishing the role of 2D materials for improving thermoelectric properties. (C) 2016 Elsevier B.V. All rights reserved.