Direct epitaxial growth of semiconducting β-FeSi₂ thin films on Si(111) by facing targets direct-current sputtering

Semiconducting Β-Fe Si2 thin films were epitaxially as-grown on Si(111) substrates at a substrate temperature of 600 °C, which is at least 200 °C lower than ordinary annealing temperatures, by using the facing targets direct-current sputtering (FTDCS) method using an Fe Si2 target without annealing. The deposited film exhibits a smooth surface with a surface roughness root mean square of 1.47 nm. The direct and indirect optical band gaps estimated from the experiment were in agreement with those of the single crystalline bulk. Temperature dependence of the electrical conductivity implied Co incorporation from the Fe Si2 targets with a purity of 3N. The FTDCS method, in which a substrate is free of plasma and energetic neutral atoms diffused into the substrate owing to low Ar pressure sputtering, is effective for the direct epitaxial growth of Β-Fe Si2 thin films with smooth surfaces.