Structural Investigation of Gold Induced Crystallization in Hydrogenated Amorphous Silicon Thin Films

Thin bilayers of glow discharge produced hydrogenated amorphous silicon (a-Si:H) and vacuum evaporated gold were annealed at different temperatures to investigate the metal induced crystallization of a-Si:H. The process of crystallization was studied by Transmission Electron Microscopy and Electron Diffraction, Auger electron spectroscopy (AES), glancing angle X-ray diffraction (XRD) and Raman spectroscopy. The results indicate that the crystallization of silicon is mediated via formation of two randomly dispersed metastable phases of gold silicide in the host matrix. Both the silicides were found to have cubic symmetry with the same lattice constant of 6.52 Å. These silicides first appear at 130° C and are stable up to 170° C. Between 170-200° C the silicides dissociate to form polycrystalline silicon.