Electron-spin-echo envelope-modulation study of the distance between dangling bonds and hydrogen atoms in hydrogenated amorphous silicon

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Abstract
Using the electron-spin-echo envelope-modulation method of pulsed electron spin resonance (ESR) technique, the spatial distribution of deuterium (chemically equivalent to hydrogen) nearby dangling-bond defects (g=2.0055) in deuterated amorphous silicon was investigated before and after light soaking. It is found, for both native and photocreated defects that the dangling bond is formed in the hydrogen-depleted region, being separated from the closest hydrogen atom by a distance of 4.2 Å (4.8 Å in the case of two closest hydrogen atoms), as estimated by using the point-dipole approximation. In both of two ESR signals (g=2.004, 2.013) under illumination (LESR), modulation is weaker than that of dangling bonds (g=2.0055), indicating a larger distance (4.8 Å to the closest hydrogen atom or 5.3 Å to the two closest hydrogen atoms by use of the point-dipole approximation). Defect-creation models, which have been proposed to explain the photoinduced metastability, are examined at a microscopic level.