Transient phases of a-Si by rapid heating

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Abstract
A structural model of a‐Si and a model for its transient phases have been proposed. In these models, it is assumed that a‐Si is composed of many small regions (or clusters with a radius of about 50 Å) having different free energies. When a‐Si is rapidly heated to a temperature slightly less than 1450 K so as to avoid crystallization, it transforms to a new phase in which both a‐Si clusters and super‐cooled l‐Si coexist. By using these models, anomalous phenomena observed in explosive crystallization and enhanced diffusion phenomena in rapid thermal annealing (RTA) process can be explained. Furthermore, the viscosity of super‐cooled Si fluid at 1000 °C induced by the RTA process is estimated to be 107–108 mPa s, which leads to the determination of T0 value of about 1300 K in Vogel–Fulcher–Tammann (VFT) relation. However, this T0 value differs from that previously reported. This discrepancy has been discussed and it is concluded that T0 in the VFT relation is not a constant but a function of (dT/dt).