Characterization of Bi₂Te₃ thin films for application in micro-thermo electric coolers

In this study we have characterized the mechanical and electrical properties of Bi₂Te₃ thin films prepared by co-sputtering method. The film structure and morphology were revealed using the X-ray diffraction and scanning electron microscopy (SEM). Thickness of the deposited films was measured using SEM observation after FIB (Focused Ion Beam) milling, and the surface roughness of the films was analyzed using AFM (atomic force microscopy). Electrical transport properties were measured with a Hall effect measurement system, while the mechanical properties were evaluated using nanoindentation test method. Results showed that Bi₂Te₃ thin films have amorphous structure at lower film thicknesses, but as the thickness increases the structure becomes polycrystalline. Surface roughness and crystal size of the films increased with increase in substrate temperature. Films showed higher elastic modulus and hardness values compared to those of the bulk Bi₂Te₃ alloy. The electrical transport properties of the films were also affected by the substrate temperature.