How UV light lowers the conductivity of SrTiO₃ by photochemical water splitting at elevated temperature

Abstract

Nominally undoped SrTiO3 single crystals were illuminated by UV light at 350 °C in oxidizing as well as reducing atmospheres. In N2/O2 atmospheres, UV irradiation enhances the conductivity of SrTiO3...

UV-Driven Oxygen Surface Exchange and Stoichiometry Changes in a Thin-Film, Nondilute Mixed Ionic Electronic Conductor, Sr(Ti,Fe)O3-d

“…12−14 Surface reactions tend to be quicker than bulk diffusion through thick samples at elevated temperature and can be difficult to access precisely in this configuration through relaxation studies. Two reported exceptions are 1) when the bulk diffusivity is apparently enhanced over the surface exchange coefficient by UV illumination in very O 2 -poor environments 14 or 2) sufficiently thin single crystals are employed, perhaps with a particular surface chemistry that enables slower surface exchange than bulk diffusion. The SrTiO 3 :Fe single crystal studies by Merkle et al 7,15 are the only ones to report apparent surface exchange coefficients in light vs dark under typical O 2rich conditions.…”

“…The oxygen chemical potential (or quasi chemical potential) may vary in a complex way with respect to depth. 13,14 Therefore, in the present work we study thin films where a) film thickness is on the order of the absorption length, and b) kinetics are expected to be limited by oxygen surface exchange at the solid−gas interface rather than by diffusion (at least in the dark), if in fact oxygen is transferred.…”