Defects on the Si(001)/SiO2 interface were studied by using the electron paramagnetic resonance technique. Advantage was taken of the high specific surface area of porous Si. The interface was characterized by the presence of 2 interfacial defects: Pb0 and Pb1. A detailed study was made here of the Pb1 defect which, in spite of being a predominant defect in this interface, had previously evaded detailed electron paramagnetic resonance investigation; due to sensitivity limitations. The Pb1 defect was characterized by a spin of S = ½, monoclinic I point symmetry, and principal g-tensor values of g1 = 2.0058, g2 = 2.0029 and g3 = 2.0069. Unlike the Pb and Pb0 defects, its line-width of 4.5G was isotropic and frequency-independent; thus indicating an atomic configuration that was not affected by stress distributions. The central 29Si hyperfine interaction of the Pb1 defect was at least a factor of 2 smaller than that of the Pb and Pb0 defects. This implied a delocalization of its electron wave function over more than one Si nucleus. The properties of the Pb1 defect were compatible with a dangling-bond defect on a Si dimer.

J.L.Cantin, M.Schoisswohl, H.J.Von Bardeleben, N.H.Zoubir, M.Vergnat: Physical Review B, 1995, 52[16], R11599-602