The energy gap of pristine silicon clusters

Studies of the fundamental energy gap of pristine silicon clusters have bee n performed using STM and STS. Clusters with sizes between 2.5 and 40 Angst rom are studied. The size dependence of the gap is determined. For particle s below 15 Angstrom, gaps up to 450 meV are found. Larger particles exhibit zero gaps. The results are explained in terms of a transformation from dia mond to compact structure occurring at 15 Angstrom (similar to 44 atoms per cluster). For clusters with diamond structure the surface dangling bond de nsity is high leading to electronic states filling the energy gap. On the o ther hand, the compact arrangement of the smaller clusters tends to elimina te dangling bonds. Therefore, finite-gap values are observed for clusters w ith less than similar to 44 atoms. (C) 2000 Elsevier Science B.V. All right s reserved.