Influence of Ti on CoSi2 nucleation

Evidence is presented that impurities present in the precursor phase may influence the nucleation of a new phase. In case of the ${\mathrm{CoSi\to CoSi}}_{\mathrm{2}}$ transition, it is found that the presence of small amounts of Ti (originating from either a Ti capping layer or interlayer) causes an increase in the ${\mathrm{CoSi}}_{\mathrm{2}}$ nucleation temperature. Moreover, for an increasing amount of Ti, we observed a transition from polycrystalline ${\mathrm{CoSi}}_{\mathrm{2}}$ over preferential (220) orientation towards epitaxial (400) ${\mathrm{CoSi}}_{\mathrm{2}}.$ The model that we propose entails a new point of view on the mechanism of Ti interlayer mediated epitaxy.