Growth mechanism and morphology of semiconducting FeSi2 films

Semiconducting β-FeSi2 films grown on (100)-oriented Si and on (11̄02)-sapphire substrates are investigated by x-ray diffraction, Nomarski optical microscopy, stress, and surface roughness measurements. As a result of an exothermic, nucleation controlled reaction, we observe a characteristic ring-shaped surface pattern of the silicide. Surface roughness and stress in β-FeSi2 are less pronounced for films grown at lower temperatures and cooling rates. Sapphire substrates result in smoother surfaces than Si due to the match of the thermal expansion coefficient of sapphire to the silicides.