Physisorption of a small aromatic hydrocarbon: Benzene on In₂O₃(111)

Abstract

In2O3 is a complex oxide material with a large unit cell and its (111) surface features different combinations of bulk-like and undercoordinated In and O atoms with 3-fold symmetry. Thus, small molecules can choose their adsorption site(s) from a variety of electronically and chemically different configurations.

In this work we study benzene, the smallest organic aromatic hydrocarbon, on bare and hydroxylated In2O3(111). We find that benzene adsorbs in the vicinity of a high-symmetry site of the surface lattice, with three molecules per unit cell in symmetry-equivalent sites. Hydroxylating the In2O3(111) surface blocks the preferred adsorption site of the benzene molecules. Still, one molecule can be accommodated in the less-favorable high-symmetry spot of the surface lattice, creating an array of well-spaced single benzene molecules. Both systems are studied with temperature programmed desorption (TPD) and non-contact atomic force microscopy (ncAFM); density functional theory (DFT) calculations and molecular dynamics (MD) simulations provide further insights into the adsorption and mobility of the molecules.