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

Abstract In the present study, the effect of the presence of monolayer graphene (G) on the nanoscale electrical and thermal conductivities of Bi 2 Te 3 has been investigated. Atomic force and conducting atomic force microscopic studies show that G incorporation results in lower electrical conductivity at Bi 2 Te 3 :Graphene (Bi 2 Te 3 :G) interfaces. The Kelvin probe and scanning thermal images show that Bi 2 Te 3 composites have different work function and thermal conductivity values compared to Bi 2 Te 3 sample. The decrease in the value of thermal conductivity was further confirmed by measuring the thermoelectric properties of Bi 2 Te 3 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 Bi 2 Te 3 /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.