EPR AND ENDOR STUDY OF THE P-B CENTER IN POROUS SILICON

The Pb center at the (111) Si-SiO2 interface has been studied with electron-nuclear-double-resonance (ENDOR) spectroscopy taking advantage of the high specific interface area of oxidized porous Si samples. The ENDOR spectrum consists only of two structureless lines at the Larmor frequencies of H1 and F19. No hyperfine interaction with Si29 could be detected. The Pb-center1H,19F distances have been estimated in the dipole-dipole approximation to 13, which corresponds to the average Pb-center separation. The intensity ratio of the H1 and F19 ENDOR lines is stable under high-temperature vacuum annealings and hydrogen treatments. Quantitative electron-paramagnetic-resonance measurements of the central hyperfine-structure intensity confirm the assignment of the Pb center to the Si dangling-bond defect, a model recently questioned by the suggestion of a hydrogen-molecule defect. © 1994 The American Physical Society.