Multi-Axial Channeling Study of Disorder in Gold Implanted 6H-SiC
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Multi-Axial Channeling Study of Disorder in Gold Implanted 6H-SiC W. Jiang, W.J. Weber, S. Thevuthasan, and V. Shutthanandan Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, U.S.A. ABSTRACT Single-crystal wafers of 6H-SiC were irradiated at 300 K with 2 MeV Au2+ ions over fluences ranging from 0.029 to 0.8 ions/nm2. The accumulated disorder on both the Si and C sublattices in the irradiated specimens has been studied in situ using 0.94 MeV D+ channeling along , and axes. At low doses, results show that some of the Si and C defects are well aligned with the axis with more C defects shielded by the atomic rows; a higher level of C disorder is observed, which is consistent with a smaller threshold displacement energy on the C sublattice. There is only a moderate recovery of disorder, produced at and below 0.058 Au2+/nm2, during the thermal annealing at 570 K; similar behavior is observed in the higher-dose samples annealed between 720 and 870 K. The results suggest the presence of defect clusters and amorphous domains formed during the Au2+ irradiation. Reordering processes at 570 K in the weakly damaged 6H-SiC (0.12 Au2+/nm2, 300 K) appear to occur closely along the direction. INTRODUCTION Extensive investigations of irradiation-induced disorder and its recovery in silicon carbide (SiC) polytypes have been motivated by their great potential for applications in hightemperature, high-power, high-frequency and radiation-hard electronics, and new-generation energy systems as well. Recent scientific efforts have substantially improved the understanding of the damage accumulation and recovery processes in SiC and have resulted in several comprehensive review articles on the experimental investigations [1-4] and relevant theoretical models [5]. Ion-channeling methods are frequently applied in these studies due to their unique capabilities of analyzing disorder. These methods can quantitatively determine the depth profiles of disorder with identified atomic species. However, most of the previous studies based on the channeling methods were carried out only along one major crystallographic axis that may result in some invisible defects due to shadowing effects. Although angular scans around multiple axes have been widely applied to determine the site locations of implants [6] (interstitial or substitutional) and lattice displacements of host atoms [7] in crystal structures, there are only a few studies reported for the accumulation of irradiation-induced disorder in SiC by means of multi-axial channeling analysis. These studies include the analysis of Al+ and Si+ implanted 3CSiC [8] along both and channeling directions, where a ‘preferential’ amorphization process on the Si sublattice along the direction was observed due to the uniaxial irradiation-induced lattice strain along the axis. This experimental result was later confirmed by the investigation of amorphization in Ar+ irradiated 3C-SiC [9]. In addition, the accumulated disorder on the Si sublattice in 6H-SiC, derived from the in-situ channeling a
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