Low-Temperature Growth of Iron Silicide Thin Films on Silicon Substrate by Molecular Beam Epitaxy

In this work, iron silicide thin films were deposited on Si (100) substrates by molecular beam epitaxy method at 500°C. The iron silicide structures were grown with nominal thicknesses of 2 nm, 4 nm, and 6 nm. The surface morphology indicates an initial island growth mode, where nominal 2 nm and 4 nm deposits form discrete clusters with peak-to-valley heights exceeding 40 nm, before coalescing into a more continuous film at 6 nm. The crystal structure, surface morphology, local current distribution, and electrical properties were characterized using X-ray diffraction, Conductive-Atomic Force Microscopy, and four-point probe station. The 4-nm-thick α-FeSi2 thin films exhibits a tetragonal structure with a preferred (111) orientation. As the thin film thickness increased, additional α-FeSi2 (003) and cubic-Fe3Si (222) phases appeared. The surface roughness significantly decreases from 5.09 ± 0.72 nm to 1.73 ± 0.35 nm, accompanied by a more uniform current distribution. The α-FeSi2 phase formed an Ohmic contact with the Si substrate. The resistivities of iron silicide are 222.7–258.9 µΩ·cm at 77 K and 308.0–323.5 µΩ·cm at 300 K. These findings suggest that FeSi2 thin films are promising materials for stable Ohmic contacts and electrode integration on Si- and FeSi2-based semiconductor devices.