ELECTRON-SPIN-ECHO ENVELOPE-MODULATION STUDY OF THE DISTANCE BETWEEN DANGLING BONDS AND HYDROGEN-ATOMS IN HYDROGENATED AMORPHOUS-SILICON

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 angstrom (4.8 angstrom 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 angstrom to the closest hydrogen atom or 5.3 angstrom 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.