High electron mobility in randomly oriented polycrystalline BaSi2 films formed through radio-frequency sputtering

Semiconducting barium disilicide (BaSi2) is a promising material for solar cell and thermoelectric applications; hence, high-mobility films are of great importance. In this study, we achieved substantially high electron mobilities exceeding 103 cm2 V−1 s−1 at 300 K in randomly oriented polycrystalline BaSi2 films formed on Si3N4 insulating films at 600 °C through radio-frequency sputtering. The BaSi2 films consisted of small grains (<0.5 µm in diameter), and the electron concentration was in the order of 1015–1016 cm−3. Kelvin probe force microscopy revealed that the root-mean-square surface potential values were lower than 31 mV, indicating that the grain boundaries did not hinder electron transport. The potential barrier height across positively charged cracks on the surface of the BaSi2 films, wherein oxidation proceeded, was as small as 30–40 mV. These results indicate that polycrystalline BaSi2 films/insulating films with high electron mobilities are useful for various electronic device applications.