Structure and vibrational spectra of carbon clusters in SiC

Abstract

The electronic, structural and vibrational properties of small carbon interstitial and antisite clusters are investigated by ab initio methods in 3C and 4H-SiC. The defects possess sizable dissociation energies and may be formed via condensation of carbon interstitials, e.g. generated in the course of ion implantation. All considered defect complexes possess localized vibrational modes (LVM's) well above the SiC bulk phonon spectrum. In particular, the compact antisite clusters exhibit high-frequency LVM's up to 250 meV. The isotope shifts resulting from a 13 C enrichment are analyzed. In the light of these results, the photoluminescence centers DII and P−U are discussed. The dicarbon antisite is identified as a plausible key ingredient of the DII-center, whereas the carbon split-interstitial is a likely origin of the P−T centers. The comparison of the calculated and observed high-frequency modes suggests that the U-center is also a carbon-antisite based defect.

Modeling of long-term defect evolution in heavy-ion irradiated 3C-SiC: Mechanism for thermal annealing and influences of spatial correlation

“…This assumption could be safe for carbon clusters with size smaller than 4, [62][63][64] and Si-C clusters 65 due to the reported high dissociation barriers (higher than 4.0eV). For Si clusters, Hornos et al 65 have reported a binding energy of 3.16eV (with a dissociation barrier higher than 4.5eV) for di-Si interstitial clusters, which seems stable for this study.…”

“…60 Previous ab-initio studies on aggregation of C I have demonstrated that C I can be trapped by C Si and form stable carbon clusters with the configuration of di-carbon antisite. [61][62][63] Though there has been no evidence showing that Si I can be captured by antisites or C I can aggregate at Si C , we assume that interstitials can form defect clusters with antisite defects with a capture distance of 2NN. The resulting clusters are also referred as interstitial clusters in this study.…”

Theoretical Study of Carbon Clusters in Silicon Carbide Nanowires

“…21 Table 1). At Si-rich limit CSi is the most favorable configuration, followed by the C-C and (C-C) i defects.…”

“…In spite of some theoretical studies on carbon aggregates in SiC bulk [20][21][22], the investigation of carbon clusters in SiC NWs is very scarce. Motivated by the lack of studies on …”

Thermally activated charge reversibility of gallium vacancies in GaAs

“…Thus, one must be aware of possible source of errors affecting the Gibbs free energy of formation. Formation entropies suffers from errors associated with the calculation of vibrational density of states [33]. For example, the microscopic structure of the defect itself, which is possibly not obtained accurately.…”