Amorphous Ti-Si alloy formed by interdiffusion of amorphous Si and crystalline Ti multilayers

Reactions upon rapid thermal annealing of sputtered Ti-Si multilayers have been studied by cross-section and through-foil transmission electron microscopy, glancing-angle Rutherford backscattering, and x-ray diffraction. The compositions of the samples are 40 at. % Ti, 60 at. % Si and 60 at. % Ti, 40 at. % Si, and the bilayer periodicity is about 10 nm. The silicon layers in the as-deposited films are amorphous; the titanium layers are polycrystalline hcp. After a 30-s anneal at 455 °C, significant interdiffusion occurs and we observed the formation of an amorphous Ti-Si alloy by interfacial reaction. The metastable disilicide, C49 TiSi2, nucleated along with a small amount of TiSi in the sample with higher silicon content (60%) upon annealing at 550 °C for 10 s, but the amorphous alloy remained as the only product of reaction in the 40-at. % Si sample.