Coordination Chemistry and Kinetics of Preferential Etching on Surfaces of TiO2 (Rutile)

Three different types of etch pits were observed on the (001) surfaces of rutile after etching in a KHSO4 flux at temperatures between 400 and 550C. A chemical reaction scheme is presented, which along with a consideration of the surface chemistry of the various crystallographic faces, is used to explain the kinetics of dissolution of the substrate and hence the observed shapes of the etch pits. Etching of a defect is enhanced in surface regions where silver is photochemically deposited and removed prior to the etching. This phenomenon is explained in terms of a hole (or electron) trapping mechanism at a crystal defect. (Author)