STRUCTURAL RELAXATION IN AMORPHOUS-SILICON PREPARED BY ION-IMPLANTATION

Structural relaxation processes in amorphous silicon (a-Si) prepared by Si+, Ge+ and P+ implantation into Si at room temperature were investigated by Raman spectroscopy, electron spin resonance (ESR), and positron annihilation. Raman measurements indicated that the average bond angle deviation DELTAtheta in a-Si networks first decreased with low temperature (200-450-degrees-C) annealing, but slightly increased with the annealing time. Based upon ESR and positron annihilation measurements, the density of dangling bonds and the free volume (e.g. microvoids) in a-Si layers were found to behave in a similar manner as DELTAtheta during thermal treatments. We propose the following model for the results described above. Microvoids stored in the a-Si layer are annihilated and/or dissociated, which results in an increase in DELTAtheta or dangling bond densities.