√21× √21 phase formed by Na adsorption on Si(111)√3× √3-Ag and its electronic structure

Abstract

Through electron diffraction observations, we found a √21× √21 phase formation by Na adsorption of 0.1∼ 0.2 ML on a Si(111)√3× √3-Ag surface below 250K. Its electronic structure was investigated by angle-resolved photoemission spectroscopy using synchrotron radiation. The phase was found to be metallic. At least six different states were identified as surface states within the bulk band gap, whose dispersions were determined along a primary symmetry direction. The observed two-dimensional band structure had a very close resemblance with those of √21× √21 phases induced by noble-metal adsorption on the same substrate. [DOI: 10.1380/ejssnt.2005.107]