RBS/simulated annealing analysis of silicide formation in Fe/Si systems

Thin Fe films were deposited by de sputtering onto Si to thicknesses between 50 and 120 nm. This was followed by implantation of 350 keV As to doses between 5 x 10(15) and 2.5 x 10(16) cm(-2), or 300 keV Xe to doses between 5 x 1015 and 1 x 10(16) cm(-2). Some of the samples were subsequently annealed at 900 degrees C for 2.5 h. The mixing between the Si and Fe was studied with Rutherford backscattering (RBS). The analysis of the RES data was done with the combinatorial optimisation simulated annealing (SA) algorithm. Although a homogeneous silicide layer is not formed, the superposition of the Si and Fe profiles after annealing leads to the formation of regions of beta-FeSi2, as is demonstrated by temperature dependent photoabsorption experiments which show the existence of a band gap of 0.87 eV at room temperature. (C) 1998 Elsevier Science B.V.