Raman and electron paramagnetic resonance studies of spark-processed Si and Ge

Raman and electron paramagnetic resonance (EPR) spectra are investigated on spark-processed Si (sp-Si) and Ge (sp-Ge), which strongly luminesce in the UV/blue and green regions of the visible spectrum. The observed small shifts and broadening of the Raman signal indicate the presence of Si, and Ge particles of about 8 nm. The EPR studies revealed two distinct paramagnetic defect centers for the UV/blue luminescing sp-Si, whereas only one paramagnetic defect with reduced EPR intensity was observed for the green luminescing sp-Si. Further, no paramagnetic defect was observed for sp-Ge. The determined g-factor for spark-processed green luminescing Si and for the strongest signal in UV/blue luminescing Si was 2.0071. EPR analysis indicates that no correlation is observed for the PL intensity and electron paramagnetic defect concentration from sp-Si, and Ge.