Direct Visualization of Nearly Free Electron States Formed by Superatom Molecular Orbitals in a Li@C 60 Monolayer

• Published in: The journal of physical chemistry letters 2021-08, Vol.12 (32), p.7812-7817
• Main Authors: Sumi, Naoya, Kuklin, Artem V., Ueno, Hiroshi, Okada, Hiroshi, Ogawa, Tomoyuki, Kawachi, Kazuhiko, Kasama, Yasuhiko, Sasaki, Masahiro, Avramov, Pavel V., Ågren, Hans, Yamada, Yoichi
• Format: Article
• Language: English
• Subjects: Deposition; Molecules; Monolayers; Salts; Scanning tunneling microscopy
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.1c02246

Using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we directly determine the spatial and energetic distributions of superatom molecular orbitals (SAMOs) of an Li@C-60 monolayer adsorbed on a Cu(111) surface. Utilizing a weakly bonded [Li+@C-60] NTf2- (NTf2-: bis(trifluoromethanesulfonyl)imide) salt makes it possible to produce a Li@C-60 monolayer with high concentration of Li@C-60 molecules. Because of the very uniform adsorption geometry of Li@C-60 on Cu(111), the p(z)-SAMO, populated above the upper hemisphere of the molecule, exhibits an isotropic and delocalized nature, with an energy that is significantly lower compared to that of C-60. The isotropic overlapping of p(z)-SAMOs in the condensed monolayer of Li@C-60 results in a laterally homogeneous STM image contributing to the formation of a free-electron-like states. These findings make an important step toward further basic research and applicative utilization of Li@C-60 SAMOs.