Nature and diffusion of the self-interstitial in silicon

The authors exploit self-consistent, semi-empirical molecular orbital calculations (CNDO) for large silicon clusters to characterise self-interstitials. Hexagonal (I+) and split (100) forms (I- and probably I0) are favoured among the several forms investigated. Possible extended high-temperature forms are not discussed. The results imply Bourgoin-Corbett (1972) athermal diffusion in p-Si and low-activation energy classical motion in n-Si; local excitation enhanced motion is possible, though not verified, but local heating is unlikely. Results agree well with experiment, both for Si and in understanding the different behaviour of silicon and diamond. The energetic advantage of the split form predicted is also supported by the observed split impurity interstitials and unidentified defects, related to the self-interstitial, observed in structures similar to the split (100) form.