Compound formation between polycrystalline iron and boron thin films studied by Auger electron depth profiling

Thin film couples consisting of pure iron and pure boron were evaporated onto substrates of Si(111) and glass. Auger electron depth profiling showed that in the interface region a compound was formed during annealing which was identified by X-ray diffraction techniques as Fe 2B. The growth kinetics of the Fe 2B was investigated in the temperature range 673–773 K. The compound grows according to a parabolic rate law by the diffusion of boron through the already formed Fe 2B layer. An activation energy of 2.9 eV was determined which demonstrates that in our temperature range the usual grain boundary diffusion model is not applicable for the interdiffusion of iron and boron thin films.