Controlling the termination and photochemical reactivity of the SrTiO3(110) surface

Abstract

SrTiO₃(110) orientated crystals have been heated to temperatures between 1000 °C and 1200 °C in air, alone or in the presence of powder reservoirs of TiO₂ or Sr₃Ti₂O₇. In these conditions, the surface is terminated by two types of atomically flat terraces. One has a relatively higher surface potential and promotes the photochemical reduction of silver (it is photocathodic) and the other has a relatively lower surface potential and promotes the photochemical oxidation of lead (it is photoanodic). Measurements of the step heights between the terraces indicate that the surfaces with different properties have different terminations. By adjusting the time and temperature of the anneal, and in some cases including reservoirs of TiO₂ or Sr₃Ti₂O₇, it is possible to change the surface area fraction from 98% photocathodic to 100% photoanodic. The surface is more photocathodic when the annealing temperature is lower, the duration shorter, and if Sr₃Ti₂O₇ is present. The surface is more photoanodic if the temperature is higher, the annealing duration longer, and if TiO₂ is present. The results make it possible to control the surface potential and the ratio of photocathodic to photoanodic area on the SrTiO₃(110) surface.