  The presence of 2D electron gases at surfaces or interfaces in oxide thin
films remains a hot topic in condensed matter physics. In particular, BaBiO3
appears as a very interesting system as it was theoretically proposed that its
(001) surface should become metallic if a Bi-termination is achieved (Vildosola
et al., PRL 110, 206805 (2013)). Here we report on the preparation by pulsed
laser deposition and characterization of BaBiO3 thin films on silicon. We show
that the texture of the films can be tuned by controlling the growth
conditions, being possible to stabilize strongly (100)-textured films. We find
significant differences on the spectroscopic and transport properties between
(100)-textured and non-textured films. We rationalize these experimental
results by performing first principles calculations, which indicate the
existence of electron doping at the (100) surface. This stabilizes Bi ions in a
3+ state, shortens Bi-O bonds and reduces the electronic band gap, increasing
the surface conductivity. Our results emphasize the importance of surface
effects on the electronic properties of perovskites, and provide strategies to
design novel oxide heterostructures with potential interface-related 2D
electron gases.
