Equilibrium configurations and electronic structure of fullerene ultrathin films on SrTiO3(001) surface

• Published in: Applied surface science Vol. 635; p. 157768
• Main Authors: Zhang, Wenxuan, Wang, Xutao, Liu, Ningning, Wang, Jinyue, Qu, Yueqiao, Guan, Dan-Dan, Wang, Shiyong, Zheng, Hao, Li, Yao-Yi, Liu, Canhua, Jia, Jin-Feng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.10.2023
• Subjects: C60; HOMO-LUMO gap; Scanning tunneling microscopy; SrTiO3; Thin films; Thin films; SrTiO3; Scanning tunneling microscopy; C60; HOMO-LUMO gap
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2023.157768

[Display omitted] •Monolayer C60 film is grown on a SrTiO3(001) surface for the first time.•Monolayer C60 exhibit a short-range ordered molecular arrangement, while multi-layer C60 show a quasi-(2 × 2) superstructure with a chiral pinwheel motif.•Monolayer C60 on STO shows the largest HOMO-LUMO gap comparing to those on any other substrates. Ultrathin fullerene (C60) films on various metal and semiconductor substrates have been intensively studied but not yet on a perovskite oxide substrate. Using scanning tunneling microscopy and spectroscopy, we investigated the molecular arrangement and electronic structure of C60 ultrathin films grown on a SrTiO3(001) surface. Subject to strong coupling and weak screening from the substrate, the monolayer C60 exhibit short-range ordered molecular arrangement with disordered molecular orientation and a substantially large highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap (∼4.1 eV). In contrast, C60 in the 2nd and 3rd layers are self-assembled into hexagon lattices with a quasi-(2 × 2) superstructure resulted from the arrangement of molecular orientations showing a chiral pinwheel structure. The HOMO-LUMO gap of the multi-layer C60 further expands to ∼ 4.6 eV, very close to that of gas-phase C60, indicating a negligible inter-layer screening effect.