Composition Dependence of Crystal Structures and Electrical Properties of Ca-Mg-Si Films Prepared by Sputtering

Ca-Mg-Si ternary films were deposited at 300–335°C on (001)Al 2 O 3 substrates by a radio-frequency magnetron sputtering. Amorphous films were obtained for a wide range of compositions but not for single-phase CaMgSi. For all compositions, the electrical conductivity of the as-deposited films increased with the increase in temperature up to 400°C. The conduction type was controlled mainly by changing the Si/(Ca + Mg + Si) ratios of the films, and films with p - and n -type conductions were observed respectively with Si/(Ca + Mg + Si) ratios below 0.6 and above 0.7 along a fixed Ca/(Ca + Mg) ratio of about 0.50. A high thermoelectric power factor above 140 μW/(m K 2 ) with p -type conduction was obtained at 400°C for an amorphous-phase film.