Microdisperse iron silicide structures produced by implantation of iron ions in silicon

Iron implanted and subsequently annealed n-type Si(lll) was studied by conversion electron Mossbauer spectroscopy for phase analysis and Auger electron spectroscopy for sputter depth profiling and element mapping. During implantation (200 keV, 3 x 10(17)cm(-2), 350 degrees C) a mixture of beta- and alpha-FeSi2 is firmed and after the subsequent annealing (900 degrees C for 18 h and 1150 degrees C for 1 h) a complete transition to the beta- and the alpha-phase can be detected. The as-implanted profile has Gaussian shape and is broadening during annealing at 900 degrees C to a plateau-like profile and shows only a slight broadening and depth depending fluctuations of the iron concentration after the 1150 degrees C annealing. With scanning Anger electron spectroscopy the lateral iron and silicon distribution were investigated and show for the sample annealed at 900 degrees C large separated beta-FeSi2 precipitates which grow due to the process of Ostwald ripening. At 1150 degrees C additionally coalescence of the precipitates occur and a wide extended penetration alpha-FeSi2 network structure is formed.