Metal thin-film nanophases and their interface with silicon

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 degrees C and, after annealing at T=250 degrees 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.