Controlling the Relative Areas of Photocathodic and Photoanodic Terraces on the SrTiO3(111) Surface

SrTiO3(111) surfaces have been heated in air at 1250 °C, either alone or with reservoirs of TiO2 and SrTiO3 powders. The surface structure and properties were measured by atomic force microscopy, scanning Kelvin probe microscopy, X-ray photoelectron spectroscopy (XPS), and photochemical marker reactions that leave solid products on the surface at the site of the photochemical reaction. All of the surfaces are made up of atomically flat terraces of two distinguishable types. One terrace has a relatively higher surface potential and promotes the photochemical reduction of Ag+. The other terrace has a relatively lower positive potential and promotes the photochemical oxidation of Pb2+. XPS measurements show that the concentration of titanium at the surface increases with the fraction of TiO2 in the powder reservoir during annealing, and marker reactions show the fraction of terraces that promote oxidation increases with the titanium content. The fractional area of terraces that promote oxidation was controlled between 45% and 86% of the total area.