Transmission electron microscopy of silicides nucleated in Y-Si reaction system

The nucleation of silicides was examined by transmission electron microscop y in a Y-Si reaction system, in which the Y layer was deposited on the Si s ubstrate at 330 degrees C. It was revealed that the amorphization due to al loying took place and the concentration gradient was formed over the alloyi ng layer during deposition. A hexagonal YSi2 phase and a cubic Y5Si3 metast able phase were observed at the layer adjoining the Si substrate and at the midmost region of the alloying layer, respectively. This result was interp reted in the light of the proposed phenomenological theory that the silicid e phases were nucleated from the amorphous alloys with suitable composition s within the formed concentration gradient. (C) 1999 American Institute of Physics. [S0021-8979(99)06205-2].