Evaluation of phase and thermoelectric properties of thin film SrSi₂

Abstract

We firstly prepared SrSi₂ thin films on insulating substrates and measured their thermoelectric properties. Thin films of Sr–Si system were deposited on (0001) Al₂O₃ substrates by radio frequency magnetron sputtering method at various deposition temperatures and under various total deposition pressure. Constituent phases primary depend on the deposition temperature. The films deposited below 600°C consisted of amorphous or the metastable CaSi₂ structure phase. CaSi₂ structure phase was obtained at 600°C irrespective of the pressure and finally stable α-SrSi₂ (α-phase) above 700°C. The films with CaSi₂ structure phase had low power factor below 10 µW m⁻¹ K⁻² for the temperature range between 100 and 400°C. On the other hand, the film with α-phase showed p-type conduction and good thermoelectric power factor beyond 700 µW m⁻¹ K⁻² at room temperature. This value is larger than the reported value of (111) one-axis-oriented Mg₂Si films prepared by the same deposition process, maximum 130 µW m⁻¹ K⁻² at 300°C. The present result shows that α-phase is one of the promising candidates as thermoelectric materials.