Muon Interaction with Negative-U and High-Spin-State Defects: Differentiating Between C and Si Vacancies in 4H-SiC

Abstract

Low-energy muon-spin-rotation spectroscopy (LE-μSR) is employed to study silicon and carbon vacancies in proton-irradiated 4H-SiC. We show that the implanted muon is quickly attracted to the negative Si vacancy (VSi), where it forms a paramagnetic muonium (Mu0) state, resulting in a reduction of the diamagnetic fraction. In samples with predominantly C vacancies (VC), on the other hand, the formation of Mu0 is very short lived and the muon quickly captures a second electron to form a diamagnetic Mu− state. The results are corroborated by density-functional calculations, where significant differences in the relaxation mechanism of the nearest-neighbor dangling bonds of the vacancies are discussed. We propose that the LE-μSR technique is capable of differentiating between high-spin and negative-U behavior in semiconducting materials. Finally, our findings emphasize the large potential of LE-μSR to probe near-surface semiconductor defects, a capability that is crucial for further development of many electronic and quantum technology applications.