Highly oriented epitaxial CaFe2O4 thin films on TiO2 substrates grown by pulsed-laser deposition

CaFe2O4 (CFO) is an oxide semiconductor being usable for a photocathode, but its single crystal is so-far grown only by a high-pressure bulk synthesis method. Using pulsed-laser deposition, we have obtained the (010)-oriented CFO films on TiO2 (100) substrates. The epitaxial structure included twin domains with 15 tilting from the surface normal and sixfold domains with in-plane rotations oft +/- 70 degrees with respect to the b axis of TiO2, which was explained by taking a number of probable arrangements between FeO6 and TiO6 octahedra into account. X-ray absorption spectroscopy and ultra-violet-visible-near-infrared spectroscopy measurements revealed the electronic properties similar to those of bulk and thus the CFO films would be suitable to the investigation of photocathodic performance. (C) 2017 Elsevier B.V. All rights reserved.