Effect of doping on the thermoelectric properties of iridium silicide thin films

Starting from the phase formation process analysed at the binary Ir-Si system the structure formation process and the thermoelectric properties of Fe doped Ir₃Si₅ thin films have been investigated. The films were prepared in the vicinity of the stoichiometric chemical composition, Ir₃Si₅, by means of different physical vapour deposition techniques particularly magnetron co-sputtering and electron beam co-evaporation. The amount of Fe dopant was varied between 0 and 2.5 at.%. For analysis of doping level and impurity concentration the chemical composition of the as-deposited films was investigated by means of Rutherford backscattering spectroscopy (RBS), energy dispersive X-ray analysis (EDX), and spark source mass spectrometry (SS-MS). The annealing process was studied in-situ by means of high temperature X-ray diffraction (HT-XRD) as well as by measurements of the electrical resistivity ρ and the thermopower S. The phase formation process depends very sensitively on the volume fractions of the major components Ir and Si, whereas the small concentrations of dopant did not change the sequence of formed crystalline phases. On the other hand, the thermoelectric transport properties correlate strongly with both, the structure formation process and the chemical composition of the films