TiSi mixing at room temperature: A high resolution ion backscattering study

Very thin Ti films (0–20 Å) have been deposited in ultra-high vacuum on atomically clean Si(111) surfaces. The films have been analyzed with Medium Energy Ion Scattering using the high depth resolution of this technique in combination with ion shadowing and blocking. The measurements show that mixing of Ti and Si already occurs at room temperature, for coverages below 2.8 × 10¹⁵ Ti atoms/cm². The composition of the uniformly mixed film is close to TiSi. For higher coverages no further mixing takes place and pure Ti is present on top of the ultrathin mixed film. The implications of these results for current silicide formation models are discussed.