Investigations on morphology and thermoelectric transport properties of Cu+ ion implanted bismuth telluride thin film

Abstract

Present study reports the effect of copper (Cu+) ion implantation (with different Cu concentrations of 0.5 at%, 1 at%, 1.5 at%, and 2 at%) on thermoelectric transport properties of bismuth telluride thin films. The field emission-scanning electron microscopy and atomic force microscopy results reveal the coalescence of columnar grains with the formation of pinholes in the Cu+ ion implanted samples and the evolution of morphology was explained successfully in the framework of spherical thermal spike model. X-ray diffraction and Raman scattering experiments revealed the reduction in the crystalline nature of Bi2Te3 thin films upon Cu+ ion implantation. The depth profiles for the atomic concentration of Bi, Te, and Cu were determined using Rutherford backscattering spectrometry. As a function of Cu+ ion fluences, the Bi atomic concentration gradually decreases across the Bi2Te3 thin films. The Hall-effect and Seebeck coefficient measurements demonstrate the n-type to p-type charge carrier conversion upon ion implantation. The charge carrier conversion is attributed to the high density of defect complexes in addition to implanted Cu atoms. These results show the possibility of fabricating TE micro-modules that comprises of n- and p-type semiconductors using ion implantation.