Structural and electronic properties of ordered single and multiple layers of Na on the Si(111) surface

Na-induced 3×{}1 reconstruction on the Si(111) surface was studied using a scanning tunneling microscope and other tools. Atomic images showed that this surface consisted of Na zigzag chains separated by a missing row, which covered the bulk-terminated Si(111) 1×{}1 substrate at the coverage of 2/3. Upon further deposition, a Na multilayer was grown following the Stranski-Krastanov mode. Tunneling I-V curves showed that the first layer of Na was insulating but the insulator-metal transition occurred in the second layer. We propose, based on the structural analysis, that this transition represents a two-dimensional Mott-Hubbard system.