Scanning tunneling spectroscopy of Si6H12 clusters deposited on Si(111)-(7x 7) surfaces

The adsorption structure and electronic properties of hydrogenated silicon clusters (Si6H12) deposited on Si(111)-7 x 7) surfaces were studied by usin g scanning tunneling microscopy and spectroscopy. Si6H13+ cluster ions were grown selectively in an ion trap and deposited at a kinetic energy of 12 e V, The cluster ions were converted to neutral Si6H12 on the surface and ads orbed preferentially in faulted halves of the (7 x 7) unit cell. The energy gap and apparent height of the clusters varied with the adsorption site. T he position-dependent characteristics are explained in terms of resonance t unneling in cluster states broadened by interaction with surface dangling b onds. (C) 2000 Elsevier Science B.V, All rights reserved.