SHI induced enhancement in conductivity of PbTe thin film for thermoelectric applications

PbTe thin film were synthesized using thermal evaporation and irradiated by 100 MeV Ag ions at different fluences ranging from 3x1013 and 1x1014 ions/cm2. Pristine films annealed under Ar atm at 250 deg. C for 1 hr. X-ray Diffraction (XRD) of pristine and irradiated films reveals the improvement of PbTe phase with increasing fluence. The thickness of the film is decreased from 195 nm to 150 nm after ion irradiation as indicated by Rutherford backscattering spectrometry (RBS) analysis due to the sputtering. Resistivity measurement using four probe techniques of these films shows the conductivity enhancement with ion fluence. The conductivity is found to be ∼ 6 fold at fluence 3x1013 ions/cm2 whereas it decreases to 3 fold after annealing in comparison to pristine sample. On further increasing the fluence from 3x1013 ions/cm2, the properties of the film begin to deteriorate. SHI induced modification may be explained on the basis of oxygen desorption and change in stochiometry of film during irradiation.