THE FE/SI(100) INTERFACE

The formation of iron silicides has been monitored by a variety of surface sensitive techniques spectroscopy, and low energy electron diffraction (LEED). The deposition of Fe onto Si(100) at room temperature results in layer-by-layer growth of polycrystalline Fe with some Si interdiffused into the growing film. The extent of the reaction of silicide formation is very limited at room temperature. These two observations contradict previous reports. Formation of iron silicide by solid phase epitaxy occurs at low temperature (325-degrees-C). The first compound formed can be identified as FeSi - with an additional Si layer at the surface. At 450-degrees-C the silicide film transforms to FeSi2, maintaining a layer of Si at the outer surface. In view of the low formation temperature and some LEED observations the disilicide is probably in the beta-phase. We have determined the temperature range of stability of the FeSi2 film. Thermal treatments at temperatures around 600-degrees-C produce the lateral disruption of the FeSi2 film. Iron disilicide can also be grown by evaporating Fe onto a Si substrate maintained at 350-degrees-C.