  As a prototypical Mott insulator with ferromagnetic ordering, YTiO3 (YTO) is
of great interest in the study of strong electron correlation effects and
orbital ordering. Here we report the first molecular beam epitaxy (MBE) growth
of YTO films, combined with theoretical and experimental characterization of
the electronic structure and charge transport properties. The obstacles of YTO
MBE growth are discussed and potential routes to overcome them are proposed. DC
transport and Seebeck measurements on thin films and bulk single crystals
identify p-type Arrhenius transport behavior, with an activation energy of ~
0.17 eV in thin films, consistent with the energy barrier for small hole
polaron migration from hybrid density functional theory (DFT) calculations.
Hard X-ray photoelectron spectroscopy measurements (HAXPES) show the lower
Hubbard band (LHB) at 1.1 eV below the Fermi level, whereas a Mott-Hubbard band
gap of ~1.5 eV is determined from photoluminescence (PL) measurements. These
findings provide critical insight into the electronic band structure of YTO and
related materials.
