Surface & Interface Modeling
for Emerging Nanomaterials and Devices

Adsorption of PTCDA and C60 on KBr(001): electrostatic interaction versus electronic hybridization

Qian Jia,† Wei Ji,∗,†,‡ Sarah A. Burke,∗,¶,‡ Hong-Jun Gao,§ Peter Grütter,‡ and Hong Guo‡

† Department of Physics, Renmin University of China, Beijing 100872, China

‡ Centre for the Physics of Materials and Department of Physics, McGill University, 3600 rue University,Montreal, Canada H3A 2T8

¶ Department of Physics and Astronomy the Department of Chemistry, The University of British Columbia, 6224 Agricultural Road, Vancouver, Canada V6T 1Z1

§ Institute of Physics, Chinese Academy of Sciences, PO Box 603, Beijing, 100190 China

DOI:10.1039/C5CP07999C    Publication Date: March 16, 2016


The adsorption of functional molecules on insulator surfaces is of great interest to molecular and organic electronics. Yet, the interplay of interactions between aromatic molecules and insulating substrates remains unclear. In this work, we present a systematic investigation of 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. 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. It was found that electrostatics forms 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). It is suggested that the electronic hybridization depends on the polarizability of the π-system, which may be suppressed by introducing high electron affinity atoms, e.g. O, into the molecule. The adsorption site of a molecule on an ionic crystalline surface is, therefore, predominantly determined by electrostatics. Internal charge redistributions at the molecule-substrate interfaces were found for the both systems. Besides, we investigate molecules adsorb on two-layer KBr(001) covered Cu(001), in which stronger charge redistributions are found both within molecules and for the whole systems. No hybridysation is found between PTCDA and the metal underneath, while a C-Br-Cu hybridized state is found in C60/KBr(001)/Cu(001). Since the interaction mechanism is dominated by electrostatics, it is concluded that alkali-halides are ineresting and important materails for investigation, due to the minor influence on the molecular electronic structure. The influence on electronic transport properties of the internal charge variations remains an open question, which may inspire new research fields of electronics


View: Phys. Chem. Chem. Phys.  18, 11008-11016 (2016)     arXiv:1303.6069    

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