Crescimento e investigação de fase semicondutora do siliceto de ferro

Abstract

This work deals with the production and investigation of thin films of iron silicides obtained by two different methods: the deposition of iron on silicon crystal surfaces at room temperature followed by the solid state reaction induced by heating (Solid Phase Epitaxy SPE) and deposition of iron in the hot substrates (Reactive Deposition Epitaxy RDE).The aim was find the best conditions to obtain the semiconduting phase b-FeSi2. The films were produced under different annealing conditions and analyzed in-situ and ex-situ by X-ray Photoelectron Spectroscopy (XPS), and ex-situ by Conversion Electron Mössbauer Spectroscopy (CEMS). Films of the e-FeSi and b-FeSi2 phases were obtained as well the mixtures Fe3Si + e-FeSi and e-FeSi + b-FeSi2. It was found that b-FeSi2 forms by conversion of the e-FeSi layer. The phase transformation occurs due the migration of silicon atoms from the substrate to the surface region driven by the annealling conditions. The best thermodynamic conditions for the phase transformation were met between 700 0C and 800 0C for SPE, and between 600 0C and 700 0C for the RDE samples. The most probably the diffusion of silicon through the silicide in case of RDE contrasted to the migration through iron in case of SPE, explains the different best temperature ranges.