Impact of Annealing Temperature and Carbon Doping on the Wetting and Surface Morphology of Semiconducting Iron Disilicide Formed via Radio Frequency Magnetron Sputtering

Abstract Iron disilicide (FeSi2) films were formed onto Si(111) substrates via radio-frequency magnetron sputtering at room temperature (RT) and 560°C. The effects of annealing temperature and carbon (C) doping concentration on the physical properties of FeSi2 films were investigated. For annealing conditions, the crystallinity of the unannealed FeSi2 films was enhanced after annealing. The surface of unannealed FeSi2 films consisted of many small crystallites, which were clustered after annealing at 500°C. The root mean square roughness (Rrms) of the unannealed FeSi2 films increased from 0.94 nm to 5.32 nm after air-annealing at 500°C. The surface of the unannealed FeSi2 films exhibited an average contact angle (θCA) of 102.35°, which decreased to 41.70° after annealing at 500°C. For C-doping conditions, the X-ray diffraction patterns for the undoped and C-doped FeSi2 revealed β(202/220) and β(404/440) peaks. The undoped FeSi2 film surfaces presented many small grains with grain boundaries, where the C-doped FeSi2 films displayed a finer surface. Rrms of the undoped FeSi2 film surface was 15.71 nm, which decreased to 10.59 nm for 3.0 at.% C-doped FeSi2 films. The average θCA of the undoped FeSi2 films was 108.35°, and this reduced slightly to 103.65° for 3.0 at.% C-doped films. Based on the obtained results, it was shown that the as-formed FeSi2 and FeSi2 films, after annealing at 100 and 300°C formed at Tsub of RT, together with the undoped and C-doped FeSi2 films formed at Tsub of 560°C, could potentially be employed for hydrophobic coating applications.