Analysis of correlation between irradiation produced C clusters and intentionally incorporated N impurity in SiC

In neutron-irradiated SiC, the dependence of the segregation of C atoms into C clusters on N impurity was investigated by using confocal micro-Raman spectroscopy. Two types of irradiation-produced C clusters, namely mixed sp2/sp3 C clusters and graphite clusters, were observed. The appearance of mixed sp2/sp3 C clusters giving a 1420 cm− 1 peak is an immediate consequence of irradiation. The graphite clusters are characterized by graphite D and G peaks and strongly dependent on the incorporated N impurity and irradiation fluence. In identical irradiation conditions, the density of formed graphite clusters increases with increasing doping concentration but decreases with increasing pre-irradiation annealing temperature. The detailed analysis demonstrated that the graphite cluster originates from N aggregation which provide sp2 C C pair acting as a graphite nucleus but not from NC donor.

Fig. 3. Dependence of the formation of graphite clusters in SiC neutron irradiated up to 1.67 × 1020 n/cm2 on the N-doping concentration. The L, H, and TH samples are N-doped SiC with doping concentrations of 5.0 × 1017, 1.0 × 1019, and 2.0 × 1019 cm− 3, respectively. The TH1 and TH2 samples come from same ingot.Figure optionsDownload as PowerPoint slideHighlights
► Neutron irradiation-produced sp2/sp3 C clusters and graphite clusters in SiC
► Dependence of the formation of graphite clusters on the N doping concentration
► Suppression of graphite clusters through pre-irradiation annealing treatment
► Micro-mechanism of the formation and suppression of graphite clusters