Tuning the electronic properties at the surface of BaBiO3 thin films

C. FERREYRA; F. MARCHINI; F. GULLER; U. LUDERS; C. ALBORNOZ; G. LEYVA; F. WILLIAMS; A. LLOIS; V. VILDOSOLA; D. RUBI

Conferencia; European Materials Research Society (EMRS) Fall Meeting 2016; 2016

Bulk BaBiO3 is a fascinating material, presenting a very rich phase diagram with a charge density wave insulating phase that is suppressed upon doping, giving place to high-TC superconductivity. Recently, it has been theoretically suggested that the (001) BaBiO3 surface should become metallic if a Bi-termination is achieved (V. Vildosola et al., Phys. Rev. Lett. 110, 206805 (2013)). This metallic state presents a 2D character and has a very promising potential in the field of oxide electronics. The experimental confirmation of this prediction, which is extremely challenging, remains lacking due to the absence of low-mismatch substrates.Here we follow a different approach by growing and characterizing (100) highly textured (but not epitaxial) BaBiO3 thin films on silicon. We show that it is possible to control the out-of-plane texture of the films by controlling the growth conditions, being possible to switch from highly (100)-textured to polycrystalline-like films. XPS spectra display an anomalous Bi doublet which is maximized for (100)-texture. The origin of this doublet is linked to our ab-initio calculations results, which suggest that electron doping stabilizes Bi3+ species and shortens Bi-O bonds at the (100)-surface. This also implies a reduction of the band gap and an increase of the surface conductivity, consistently with our transport measurements. We conclude that as the texture of the films can be easily controlled by the growth conditions, it is possible to tune the electronic properties at the surface of these films.