The Phase Transition during Post Annealing

Abstract

Abstract:We have studied why PA (post-annealing) takes a long time to restore damaged crystallinity, which corresponds to repeat 10 10 times of lattice vibrations. Using a MD (molecular dynamics) simulation, we monitored the time-series of the LRO (long-range order) parameter as LRO pattern, in the case of a type IIa diamond, from the beginning of ion impact by a sub-keV N 2 beam implantation to a few nanoseconds, i.e., close to the feasible time limit for MD simulations. Due to the ion impact, the LRO parameter changed gradually from "LRO = 1" (crystal) to "LRO = 0" (amorphous), showing the so-called critical slowing-down phenomenon. However, since PA was started the LRO pattern was not unique. The LRO patterns were grouped into more than three types of phases and the transition between them was also found. From the viewpoint of statistical dynamics, such chaotic variations in the LRO pattern may present that the system is a GCM (globally coupled map) of a complex system in a closed system. A GCM composed of coupled oscillators develops slowly to exhibit several different phases or 'chaotic itinerancy' over time. Therefore, the long duration required for PA may be attributable to the nature of a complex system.