Electronic structure evolution at DBBA/Au(111) interface W/O Bismuth insertion layer

• Published in: Synthetic metals Vol. 251; pp. 24 - 29
• Main Authors: Tian, Qiwei, He, Bingchen, Zhao, Yuan, Wang, Shitan, Xiao, Junting, Song, Fei, Wang, Yao, Lu, Yunhao, Xie, Haipeng, Huang, Han, Gao, Yongli
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.05.2019; Elsevier BV
• Subjects: Bismuth; Charge transfer; Chemical synthesis; DBBA; Dipoles; Electronic structure; Electrons; Energy levels; Evolution; Film thickness; Graphene; Insertion; PES; Photoelectric emission; Precursors; Substrates; Thin films; Work functions; DBBA; Electronic structure; Au; Bi; PES
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/j.synthmet.2019.03.016

•Revealing the electronic structure evolution of self-assembled DBBA on Au(111) and Bi-3×3-Au(111).•Showing structural difference of DBBA on Au(111) and Bi-3×3-Au(111) at molecule level.•Explaining why 7-GNRs could not be formed on Bi-3×3-Au(111). Atomically precise graphene nanoribbons (GNRs) can be on-surface synthesized from halogen containing molecular precursors. Here, we investigated the electronic structure evolution of 10,10′-dibromo-9,9′-bianthracene (DBBA), a famous precursor to 7-AGNRs, on both Au(111) and Bi-3×3-Au(111) as a function of film thickness and post-annealing temperature using photoemission spectroscopy, low temperature scanning tunneling microscopy and density functional theories. No obvious changes in electronic structure of DBBA in three STM-observed configurations can be detected, indicating that nonplanar π -conjugated DBBA is physisorbed on both surfaces. The energy level alignments at the DBBA-substrate interfaces are demonstrated. Bismuth(Bi) insertion layer makes molecular−substrate interaction weaker, and makes the energy levels of DBBA thin film rigidly shift by ˜0.70 eV away from Fermi level, which enlarges the hole injection barrier and results in DBBA desorption at ˜470 K before dehalogenation occuring. The surface work function reduction can be explained by the push back effect and charge transfer induced interface dipole. Our findings explain why 7-GNRs could not be formed on Bi-3×3-Au(111).