We have measured the kinetic rate of formation of CrSi2 using 2.0-MeV 4He + backscattering spectrometry. CrSi2 was formed on single-crystal 100- and 111-oriented Si and on Pd2Si grown on 100 Si. For both Si-Cr and Si-Pd2Si-Cr samples the rate of growth of CrSi2 is linear in time with an activation energy of 1.7±0.1 eV and a value of 0.7 Å/sec at 450°C. For all annealing temperatures, the growth becomes nonlinear at long annealing times. The nonlinearity is attributed to a contaminant, probably oxygen. On Pd2Si, CrSi2 starts to form at about 400°C, while on Si, CrSi2 formation is observed at 450°C and above. The difference in formation temperatures is due to contamination at the Si-Cr interface, quite probably a thin oxide layer. The growth rate of CrSi2 in the Si-Pd2Si-Cr samples is independent of the thickness of Pd2Si
