Gas Molecule Adsorption On Surfaces Of Indium (Tin) Oxide: Density Functional Theory Study

We performed density functional studies upon the(100)surfaces of In₂O₃ and ITO and their interactions with gas phase molecules,such as O₂,H₂O,NH₃ and C₂H₄.The calculated results indicate that In terminated surface and O terminated surface that agree with stoichiometry are real surfaces in nature.Doping into In₂O₃ with Sn shows that b site is more favorable for Sn replacement,which is consistent with experimental works and calculational studies.The aggregation of Sn on the surface layers on ITO is observed and our calculations give rise to a theoretical proof.Calculated surface energies indicate the O terminated surface is more stable under oxidizing atmosphere,which explained the original of oxygen dimer and monooxygen ions on the surface of In₂O₃ an ITO.Coupled with O terminated surface,In terminated surface exists under reducing environment.O terminate and In terminate surfaces were used in this study for the adsorption of small gas phase molecules.Competitive adsorption between H₂O and O₂ were studied on both In terminated and O terminated surfaces.It was found that In terminated surface is readily oxidized to O terminated surface once exposed to the two gases.After the fully oxidation of the surface,H₂O is much more readily dissociate on the O terminated surface rather than the In terminated surface.The hydroxylated surface layer is negatively charged.Compared with H₂O and O₂,NH₃ is weakly bonded to the surface reactive sites,resulting to a positively charged surface adsorption layer. C₂H₄ is a promising candidate for lower the injection barrier of hole in semiconductor devices due to its strong interaction with O terminated surface and the formed positively charged adsorption layer.