Thickness-induced metal to insulator transition in Ru nanosheets probed by photoemission spectroscopy: Effects of disorder and Coulomb interaction

• Published in: Scientific reports Vol. 10; no. 1; p. 1541
• Main Authors: Ootsuki, Daiki, Kodera, Kenjiro, Shimonaka, Daiya, Arita, Masashi, Namatame, Hirofumi, Taniguchi, Masaki, Minohara, Makoto, Horiba, Koji, Kumigashira, Hiroshi, Ikenaga, Eiji, Yasui, Akira, Uchimoto, Yoshiharu, Toyoda, Satoshi, Morita, Masahito, Fukuda, Katsutoshi, Yoshida, Teppei
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 30.01.2020; Nature Publishing Group UK
• Subjects: Graphene; Physical properties; Polyvinyl alcohol; Radiation; Spectroscopy; Spectrum analysis
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-58057-9

We investigated the electronic structures of mono- and few-layered Ru nanosheets (N layers (L) with N = 1, ~6, and ~9) on Si substrate by ultra-violet and x-ray photoemission spectroscopies. The spectral density of states (DOS) near E of ~6 L and 1 L is suppressed as it approaches E in contrast to that of ~9 L, which is consistent with the Ru 3 d core-level shift indicating the reduction of the metallic conductivity. A power law g(ε) ∝ |ε - ε | well reproduces the observed spectral DOS of ~6 L and 1 L. The evolution of the power factor α suggests that the transition from the metallic state of ~9 L to the 2-dimensional insulating state with the soft Coulomb gap of 1 L through the disordered 3-dimensional metallic state of ~6 L.