Metal thin-film nanophases and their interface with silicon

Abstract

Composition, electron density and morphology of metal thin-film nanophases were studied by AES, EELS, AFM and conductivity measurements during MBE deposition of Fe and Co on Si(100) and (111), respectively. AES data demonstrated a layer by layer growth of Fe with a segregation of submonolayer coverage of Si at T = 20 °C and, after annealing at T = 250 °C, a fixed and increased value of the Si-to-Fe Auger-peak ratio in the ranges of d = 0.03−0.12 or 1.2 nm and 0.3−0.6 nm, respectively. EELS spectra indicated a redistribution of valence electrons at the Fe/ Si(100) interface at d = 0.03−0.12 nm. With further increase of Fe thickness, EELS spectra showed transitions to Fe nanophases with lowered concentration of valence electrons near d = 0.12−0.3 nm and d = 0.6−1.2 nm. After annealing AFM images showed the relief stability of stepped Si(100) surface in the range of d = 0.03−0.3 nm, the disappearance of the stepped relief type after 0.3 nm and formation ridge-like islands in Fe film at d = 1.2 nm. Auger peak intensity and conductivity versus the thickness for nanophases of Co on Si(111) showed variations of growth mechanism in accordance with variations of interface layer state.