No abstract

We have investigated the kinetics of light-induced defect (dangling bond) creation and annealing processes in a-Si:H containing a large amount of hydrogen at 300 K and 77 K using the ESR technique. We have obtained direct evidence for the light-induced annealing of dangling bonds at 300 K. A model, in which nonradiative recombination of electrons and holes at hydrogen-related dangling bonds is taken into account, is presented to interpret the experimental results.

No abstract

The origin of two distinct electron paramagnetic resonance (EPR) spectra observed in Cr-doped Sn02 crystals, i.e. , (EPR)l and (EPR)», was investigated using the superposition model specifically developed for rutile-type crystals. Analytical results suggest that these spectra are due to the substitutional Cr'+ ions having a unique structure with respect to its local surrounding oxygen atoms. The (EPR)l spectrum showed that the four nearest-neighbor oxygen atoms on the (110) plane have moved from normal sites toward the Cr + ion by 0.072 A (3.5%) as a result of a reduction in the metal ionic radius. The (EPR)» spectrum showed the Cr + ion to be coupled with the vacancy of the two nearest-neighbor oxygen atoms on the [110]axis. In this case, the ratio of spin-Hamiltonian parameters takes the form E/D = -cos2a from the superposition model, where a is the angle between the [001] axis and the cation-ligand bonding axis in (110) plane. The theoretical value E/D = -0.205 was obtained from this simple relation, and was in good agreement with the experimental values.

No abstract