The formation and surface structure of pentafluorobenzeneselenolate (PFB-Se) self-assembled monolayers (SAMs) on Au(111) prepared by solution and vapor depositions were examined by scanning tunneling microscopy (STM). STM observations showed that solution-deposited PFB-Se SAMs on Au(111) had only a disordered phase containing many dark areas with irregular shapes, regardless of the deposition time. However, it was found that the degree of structural order of PFB-Se SAMs was markedly improved by the vapor deposition method at 348 K. After short deposition for 5 min, PFB-Se SAMs on Au(111) consisted of two distinct regions: a bright protruding region and a dark region with partial ordered domains. Interestingly, PFB-Se SAMs after deposition for 1 h showed various structural features with three different contrasts: an ordered dark region, an ordered and disordered bright region, and a very bright region. The ordered domain is assigned to a (5 × √3) structure. The relatively uniform and nicely ordered PFB-Se SAMs with a (14 × √3) structure were formed after longer deposition for 2 h, resulting from further adsorption and structural rearrangements. Furthermore, Kelvin probe force microscopy measurements (KPFM) exhibited a significant difference in the work function of pentafluorobenzenethiolate and the PFB-Se SAM-modified gold surface by 0.36 eV due to the large difference in the domain and packing structures of both SAMs. Herein, STM and KPFM results will give new insights into the formation and structures of PFB-Se SAMs on Au(111) and further the fundamental understanding of the interfacial electronic properties of fluorinated aromatic backbone-based thiolate and selenolate SAMs.
Bibliographical noteFunding Information:
This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education ( NRF-2018R1D1A1B07048063 , NRF-2020R1A6A1A06046728 , and NRF-2021R1A2C2010917 ). This work was also supported by the JSPS KAKENHI grant (Grant Number JP22H04530 , JP21H05511 , and JP20H05210 ) and the Research Program of "Five-star Alliance" in "NJRC Mater. & Dev."
© 2022 Elsevier B.V.
- Kelvin probe force microscopy
- Scanning tunneling microscopy
- Self-assembled monolayers
- Work function
ASJC Scopus subject areas
- Condensed Matter Physics
- Physics and Astronomy(all)
- Surfaces and Interfaces
- Surfaces, Coatings and Films