Slow-positron emission from the surfaces of as-grown n-type 4H-SiC and 6H-SiC (silicon carbide) with a conversion efficiency of ~ 10−4 has been observed. After 30 min of 1000 oC annealing in forming gas, the conversion efficiency of the n-type 6H-SiC sample was observed to be enhanced by 75% to 1.9 × 10−4, but it then dropped to ~ 10−5 upon a further 30 min annealing at 1400 oC. The positron work function of the n-type 6H-SiC was found to increase by 29% upon 1000 oC annealing. For both p-type 4H-SiC and p-type 6H-SiC materials, the conversion efficiency was of the order of ~ 10−5, some ten times lower than that for the n-type materials. This was attributed to the band bending at the p-type material surface which caused positrons to drift away from the positron emitting surface.
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