Annealing processes of vacancy-type defects in electron-irradiated and as-grown 6H-SiC studied by positron lifetime spectroscopy

Abstract

Annealing processes of vacancy-type defects in 3 MeV electron-irradiated and as-grown 6H-SiC have been studied by positron lifetime spectroscopy. Vacancy-type defects giving rise to a positron lifetime of 183 ps were detected in as-grown n-type specimens. They were found to be annealed at around 1400°C and were related to silicon vacancies, possibly complexes of silicon vacancies and nitrogen atoms. Defects related to carbon vacancies, silicon vacancies, and divacancies were found to be created by electron irradiation. The defects related to carbon vacancies and divacancies were found to be annealed up to 500°C. The defects related to silicon vacancies were found to be annealed at around 750 and 1400°C. The former annealing stage was inferred to be due to migration of silicon vacancies to internal sinks or nitrogen atoms to form complexes of silicon vacancies and nitrogen atoms. The latter annealing stage was explained as due to annihilations of the complexes as well as the case of as-grown specimens.

Ab initiostudy of the migration of intrinsic defects in3C−SiC

“…The annealing of vacancy-related defects has been studied by positron annihilation spectroscopy (PAS) 11,12,13,14 and electron paramagnetic resonance techniques (EPR) 15,16,17,18 in irradiated material. The identification of the EPR-centers as isolated silicon 15,16 and carbon 18 vacancies has been verified theoretically.…”

Clustering of vacancy defects in high-purity semi-insulating SiC

“…17 The most common polytype encountered in recent positron studies for SiC is 6H, for which several values for bulk lifetime have been proposed, in the range of 136-150 ps. 8,[14][15][16]18,[20][21][22] The theoretical calculations give lifetimes of 134 ps for 4H-SiC, 23 141 ps for 6H-SiC, and 138 ps for 3C-SiC. 11 It should be noted that different calculation schemes ͑especially different enhancement factors͒ cause differences in the resulting absolute lifetimes, which become evident when comparing results from different studies.…”

“…[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] ͒. These studies often involve irradiated materials.…”

Thermal Diffusivity of Ceramics During Neutron Irradiation

“…However, many works reported change of PAL in SiC irradiated by electron or ion beam [27][28][29][30][31][32][33]. Kawasuso et al reported that electron irradiated n-type (nitrogen-doped) 6H-SiC showed obvious change in τ ( 143 ps to 178 ps ), while p-type (aluminum-doped) 6H-SiC showed almost no change ( 136 ps to 138 ps ) [33]. The specimen was irradiated with 3 MeV electron to a fluence of 1×10 17 e − /cm 2 , that correspond to about 4×10 −6 dpa.…”