Molecular Dynamic Simulation of Cascade Overlap and Amorphization in 3C-SiC
- PDF / 206,943 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 20 Downloads / 134 Views
Molecular Dynamic Simulation of Cascade Overlap and Amorphization in 3C-SiC Fei Gao and William J. Weber Pacific Northwest National Laboratory, MS K8-93, P. O. Box 999, Richland, WA 99352, USA ABSTRACT Molecular dynamics (MD) simulations have been employed to study cascade overlap and defect accumulation processes during amorphization in 3C-SiC. A large number of 10 keV displacement cascades were randomly generated in a model crystal to achieve the amorphous state, and the corresponding dose is consistent with experimental observations. The results show that most defects are single interstitials and mono-vacancies at low dose, whereas the amorphous or disordered clusters, which consist of interstitials and antisite defects, appear at intermediate dose levels. These local disordered regions play an important role in the amorphization of SiC. At higher doses, a significant proportion of antisite defects is created during continued cascade overlap. The increase in interstitials and antisite defects with increasing dose suggests that the primary driving force for the crystalline-to-amorphous transition under these ion irradiation conditions in SiC is due to the accumulation of both Frenkel pairs and antisite defects. INTRODUCTION SiC-based materials have outstanding physical and chemical properties (e.g., wide band gap, high mechanical strength, high thermal conductivity and low activation), that makes these materials potential candidates for high-power and high-frequency application [1] and for structural components in both fusion [2] and fission [3] reactors. The loss of crystallinity or amorphization in SiC under energetic ions has been the topic of numerous studies experimentally over the last decades, leading to several comprehensive reviews [4,5]. The irradiation-induced crystalline-to amorphous (c-a) transformation also exhibits interesting physics of it own right, as noted in [5]. Therefore, the investigation of the mechanisms leading SiC to disordering and amorphization by irradiation represents an important challenging issue from both a scientific and technological point of view. The experiments on SiC irradiated using ion beams [6,7] and electrons [8,9] have demonstrated that there is a c-a transformation below a critical temperature that depends on the irradiation conditions. These results suggest that amorphization in SiC is dominated by a defectstimulated amorphization process that is associated with the accumulation of irradiation-induced defects or the overlap of damage cascades. However, it is still unclear how antisite defects and Frenkel pairs play a role and how amorphous clusters are nucleated during the process of defect accumulation. This demands computer simulations to characterize the damage accumulation due to cascade overlap and obtain a fundamental understanding the atomic-level process controlling the c-a transition. In this paper, molecular dynamics (MD) simulations have been employed to study cascade overlap, defect accumulation and irradiation-induced amorphization in 3C-SiC and the initi
Data Loading...
