A valence-selective X-ray fluorescence holography study of an yttrium oxide thin film

The first direct valence-selective structure determination by X-ray fluorescence holography is reported. The method is applied to investigate an epitaxial thin film of the rare earth monoxide YO, which has recently been synthesized by pulsed laser deposition. The surface of the sample is easily oxidized to Y₂O₃. In order to separate the structural information connected with the two different valence states of Y, the X-ray fluorescence holography measurements were performed close to the Y K absorption edge. Using the shift of the absorption edge for the different valence states, very different relative contributions of YO and Y₂O₃ are obtained. Thus, it is possible to distinguish the crystal structures of YO and Y₂O₃ in the thin-film sample.