Electrical Properties of (110)-Oriented Nondoped Mg2Si Films with p-Type Conduction Prepared by RF Magnetron Sputtering Method

Magnesium silicide (Mg2Si) thick films with (110) orientation were fabricated on (001) sapphire substrate using radiofrequency magnetron sputtering. Stoichiometric Mg2Si films with composition Si/(Mg + Si) = 0.33 were achieved over a range of vacuum from 10 mTorr to 140 mTorr and 300°C. On postannealing the film at 500°C, the out-of-plane lattice parameter shifted to lower values and the electrical conductivity increased by two orders of magnitude. A room-temperature Seebeck coefficient of 517 μV K−1 was observed and found to decrease with increasing temperature; the Seebeck coefficient remained at a constant positive value of 212 μV K−1 at 500°C. This can be related to the possibility of p-type conduction in this temperature range.