It was recalled that 2 types of defect (dangling bonds, floating bonds) were possible candidates as the source of electron spin resonance signals. Structural models were developed here which contained only one type of defect. By using a tight-binding approach with an on-site Hubbard U-term it was shown that, for physically reasonable values of U (0.1 to 1eV), only dangling bonds gave rise to local magnetic moments. Floating bonds gave only tiny moments, and continuous random networks gave none. The local magnetic moments and local charges could be understood in terms of bond-angle distributions. Hyperfine data were also consistent with the dangling-bond explanation.

Electron Spin Resonance Signals in a–Si - Dangling Versus Floating Bonds S.Knief, W.Von Niessen: Physical Review B, 1999, 60[8], 5412-6