title: Adsorption of PTCDA and C₆₀ on KBr(001): electrostatic interaction versus electronic hybridization.
abstract: The adsorption of functional molecules on insulator surfaces is of great interest to molecular and organic electronics. Here, we present a systematic investigation of the geometric and electronic properties of perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) and C60 on KBr(001) using density functional theory and non-contact atomic force microscopy to reveal the interplay of interactions between aromatic molecules and insulating substrates. Energetic and structural details are discussed, as well as electronic structures, e.g. local electronic density of states, (differential) charge density, and Bader charge analysis, were inspected. Electrostatics was found to be the primary interaction mechanism for systems of PTCDA and C60 adsorbed on KBr, which can be further promoted by electronic hybridizations of non-polar, but polarizable, molecules with substrates, e.g. C60/KBr(001). Electronic hybridization, depending on the polarizability of the π-system, may be suppressed by introducing high electron affinity atoms, e.g. O, into the molecule. Besides, we investigate molecules adsorbed on two-layer KBr(001) covered Cu(001), in which no hybridisation was found between PTCDA and the metal underneath, but a C-Br-Cu hybridized state in C60/KBr(001)/Cu(001). Since the interaction mechanism is dominated by electrostatics, it is concluded that alkali-halides are interesting and important materials for investigation, due to the minor influence on the molecular electronic structure, which may inspire new research fields of electronics.
authors.affiliation: Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China. wji@ruc.edu.cn.
authors.forename: Qian
authors.initials: Q
authors.lastname: Jia
authors.affiliation: Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China. wji@ruc.edu.cn.
authors.forename: Zhi-Xin
authors.initials: ZX
authors.lastname: Hu
authors.affiliation: Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China. wji@ruc.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Ji
authors.affiliation: Department of Physics and Astronomy, the Department of Chemistry, and Stewart Blusson Quantum Matter Institute, The University of British Columbia, 6224 Agricultural Road, Vancouver, Canada V6T 1Z1. saburke@phas.ubc.ca.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Burke
authors.affiliation: Institute of Physics, Chinese Academy of Sciences, PO Box 603, Beijing, 100190 China.
authors.forename: Hong-Jun
authors.initials: HJ
authors.lastname: Gao
authors.affiliation: Centre for the Physics of Materials and Department of Physics, McGill University, 3600 rue University, Montreal, Canada H3A 2T8.
authors.forename: Peter
authors.initials: P
authors.lastname: Grütter
authors.affiliation: Centre for the Physics of Materials and Department of Physics, McGill University, 3600 rue University, Montreal, Canada H3A 2T8.
authors.forename: Hong
authors.initials: H
authors.lastname: Guo
mesh_terms: D000812:Anhydrides / Q000737:chemistry*; D001965:Bromides / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D010569:Perylene / Q000031:analogs & derivatives* / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry*; D055672:Static Electricity
chemical_list: C521594:3,4,9,10-perylenetetracarboxylic dianhydride; D000812:Anhydrides; D001965:Bromides; D017680:Potassium Compounds; D010569:Perylene; C039004:potassium bromide