Interfacial engineering of optical absorption in epitaxial LaCrO$_{3}$-SrTiO$_{3}$ superlattices

SrTiO$_{3}$ (STO) is a wide-gap semiconductor well suited for photocatalytic H$_{2}$ production due to the alignment of its band edges with the half-cell energies of the H$_{2}$O redox reactions. However, the wide optical gap of STO (3.3 eV) makes the material an inefficient light absorber in the visible spectrum, preventing formation of electron-hole pairs needed for photocatalysis. Superlattice films comprised of alternating layers of band insulator SrTiO$_{3}$ and Mott insulator LaCrO$_{3}$ (LCO) have been theoretically predicted to offer intriguing optical properties due to the broken symmetry between the unoccupied Ti d$_{\mathrm{xy}}$ and Ti d$_{\mathrm{xz}}$ and d$_{\mathrm{yz}}$ orbitals. In this work, we examine the properties of LCO-STO superlattices grown with various periodicities on (La,Sr)(Al,Ta)O$_{3}$ (LSAT) (001) substrates using oxide molecular beam epitaxy. Films were characterized via \textit{in situ} x-ray photoelectron spectroscopy to measure valence band structure and interfacial band bending. Polarized Ti and Cr K-edge x-ray absorption near edge spectroscopy was used to examine the bonding anisotropy. Spectroscopic ellipsometry measurements show the presence of interfacially-induced visible light absorption not found in either STO or LCO.