Growth and Characterization of Barium Oxide Nanoclusters on YSZ(111)

Barium oxide (BaO) was grown on a yttria-stabilized zirconia (YSZ) substrate by oxygen plasma-assisted molecular beam epitaxy. In situ reflection high-energy electron diffraction, ex situ X-ray diffraction (XRD), atomic force microscopy, and X-ray photoelectron spectroscopy (XPS) have confirmed that BaO grows as clusters on YSZ(111). During and following growth under ultrahigh vacuum conditions, we found BaO remained in single phase. When exposed to ambient conditions, the clusters transformed to BaCO 3 and/or Ba(OH) 2 H 2 O. However, in a few attempts of BaO growth, XRD results show a fairly single-phase cubic BaO with a lattice constant of 0.5418(1) nm. XPS results show that exposing BaO clusters to ambient conditions resulted in the formation of BaCO 3 on the surface and partly Ba(OH) 2 throughout the bulk. On the basis of the observations, it is concluded that the BaO nanoclusters grown on YSZ(111) are highly reactive in ambient conditions.