Electronic properties of assembled islands of hydrogen-saturated silicon clusters on Si(111)-( 7 x7) surfaces studied by scanning tunneling spectroscopy

Abstract

We present results of scanning tunneling spectroscopy (STS) measurements of hydrogen-saturated silicon clusters islands formed on Si(111)-( 7×7) surfaces. Nanometer-size islands of Si6H12 with a height of 0.2-4 nm were assembled with a scanning tunneling microscope (STM) using a tip-to-sample voltage larger than 3 V. STS spectra of Si6H12 cluster islands show characteristic peaks originating in resonance tunneling through discrete states of the clusters. The peak positions change little with island height, while the peak width shows a tendency of narrowing for the tall islands. The peak narrowing is interpreted as increase of lifetime of electron trapped at the cluster states. The lifetime was as short as 10-13 s resulting from interaction with the dangling bonds of surface atoms, which prevents charge accumulation at the cluster islands.