Copper-related defects in silicon: Electron-paramagnetic-resonance identification

In this paper the observation of two electron-paramagnetic-resonance spectra, both present in p-type silicon samples after doping with silver, is reported. The two centers show a symmetry lower than cubic and have an effective electron spin $S=1/2$. In view of the detected hyperfine interaction with nuclear spins $I=3/2$, the spectra are shown to be related to a contaminant introduced into the samples during the diffusion process. By analysis of the features of the spectrum and the defect formation, a spectrum of the tetragonal symmetry, labeled Si-NL58, is identified as a copper-copper pair in a negatively charged state. The second spectrum, labeled Si-NL59, is attributed to a complex containing one copper atom.