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

The adsorption structure and electronic properties of hydrogenated silicon clusters (Si6H12) deposited on Si(111)-(7×7) surfaces were studied by using scanning tunneling microscopy and spectroscopy. Si6H+13 cluster ions were grown selectively in an ion trap and deposited at a kinetic energy of 12 eV. The cluster ions were converted to neutral Si6H12 on the surface and adsorbed preferentially in faulted halves of the (7×7) unit cell. The energy gap and apparent height of the clusters varied with the adsorption site. The position-dependent characteristics are explained in terms of resonance tunneling in cluster states broadened by interaction with surface dangling bonds.