Simultaneous improvement in electron transport and phonon scattering properties in Bi2Te3:Si nanocomposite thin films: Role of a conducting secondary phase

Abstract

In the present study, thin films of Bi2Te3 and Bi2Te3:Si nanocomposites, with varying concentration of Si, have been synthesized using co-sputtering technique. The effect of concentration of Si secondary phase segregated along Bi2Te3 crystallite boundaries on electrical and thermal properties of Bi2Te3:Si nanocomposite thin films has been investigated. Structural and morphological studies were carried out using X-ray diffraction and scanning electron microscopy. X-ray diffraction revealed the effect of Si incorporation on orientation and structural changes of the deposited composite thin films. Hall measurements were carried out in the temperature range 100–300 K and value of ZT was determined at room temperature using Harman's four probe technique. The obtained values of ZT were correlated with the changes in the carrier concentration and mobility of the deposited samples. The effect of Si concentration on the thermal conductivity of Bi2Te3:Si nanocomposites at nanoscale level was investigated using scanning thermal microscopic studies. Incorporation of optimized concentration of Si (4%) results in change in electronic properties due to modification in crystallite orientation, and the presence of a secondary conducting phase along Bi2Te3 crystallites, which results in higher electron transport and increased phonon scattering.