Site-resolved electronic structure of Al nanocluster fabricated on Si(111) 7 × 7 surface

Abstract

We have done scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS) as well as current imaging tunneling spectroscopy (CITS) of an Al nanocluster periodic array of a submonolayer-Al/Si(111) system. To understand the formation mechanism of this system in detail, a phase diagram of the Al/Si(111) has been carefully produced. Among several structural phases, the nanocluster phase appears for the deposition thickness of 0.24-0.5 ML at a substrate temperature of 550° C. It has been confirmed that these growth conditions should be carefully chosen to produce the well-defined nanocluster. The site-resolved STS spectra of Al nanocluster at 78 K show an insulating energy gap of 3.3 eV. In the CITS images, we have found different features of space-resolved tunneling current for the filled and empty states, which markedly depend on atomic sites and also on inequivalent half-unit cells. © 2006 The Surface Science Society of Japan.