Density Functional Study of the Cluster Model of SnO 2 (110) Surface Modified by Benzoic Acids

Abstract

The properties of the modified surface of SnO 2 (110) with benzoic acid (Y-C 6 H 4 -COOH: Y is para position relative to -COOH group) derivatives were investigated using density functional theory. Zehner et al. mentioned that the modifica-tion of surface dipole moment made it possible to tune the work function of the system. The experiment of Ganzorig et al. showed that there was a linear relationship between the dipole moment of the binding molecule and the work func-tion change of the system using the modified surface of indium-tin oxide (ITO) with some benzoic acid derivatives. To elucidate the relation between the dipole moment of the molecule and the work function change, we investigated the modified surface of SnO 2 (110) using Sn 7 O 14 cluster model which was embedded in the fixed point charges. On the modification of the surface, benzoic acid derivatives were bound to SnO 2 surface. By changing the terminal group of benzoic acid with H, Cl, F, CF 3 and CCl 3 , the work function changed and the dipole moment of the binding molecules of the modified SnO 2 (110) were evaluated. The results showed that there was a linear relationship between the dipole moment of the binding molecules and the work function changed. From this relation, the average value of the dipole moments of Sn-OOC linkage at the surface was also evaluated.