Nickel ͑Ni͒ induced crystallization of amorphous silicon (a-Si) has been studied by selective deposition of Ni on a-Si thin films. The a-Si under and near the Ni-covered regions was found to be crystallized after heat treatment at 500°C from 1 to 90 h. Micro-Auger electron spectroscopy revealed that a large amount of Ni stayed in the region under the original Ni coverage, but no Ni was detected either in the crystallized region next to the Ni coverage or in the amorphous region beyond the front of the laterally crystallized Si. X-ray photoelectron spectroscopy revealed a nonuniform Ni distribution through the depth of the crystallized film under the original Ni coverage. In particular, a Ni concentration peak was found to exist at the interface of the crystallized Si and the buried oxide. It was found that a layer of 5-nm-thick Ni could effectively induce lateral crystallization of over 100 m of a-Si, but the lateral crystallization rate was found to decrease upon extended heat treatment. Transmission electron microscopy analysis showed that the crystallized film under the Ni coverage was composed of randomly oriented fine grains, while that outside the Ni coverage was mainly composed of large ͑110͒-oriented grains. A unified mechanism is proposed to explain the Ni induced crystallization of a-Si and possible reasons for the reduction in the lateral crystallization rate are discussed.

An accelerated random sequential adsorption process is studied as a model of chemisorption on a line with precursor layer diffusion. In this process if the position first selected for deposition is occupied then the particle diffuses and is absorbed on the first vacant position it visits. For k-mer deposition exact results are obtained for the gap distribution function. Physically measurable quantities such as the average island size and the probabilities of island nucleation, growth and coagulation are calculated as a function of coverage and the saturation coverage is calculated as a function of k. The continuum version of this model is also considered and potential applications of the models are discussed. §

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