X-ray photoelectron spectroscopy and diffraction investigation of a metal-oxide-semiconductor heterostructure: Pt/Gd₂O₃/Si(111)

Platinum thin films deposited by physical vapor deposition (PVD) on Gd₂O₃/Si(111) templates are investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray photoelectron diffraction (XPD). Both XRD and XPD give clear evidence that Gd₂O₃ grows (111)-oriented and single-domain on Si(111) with mirror epitaxial relationship viz.; [1¯10] Gd₂O₃(111)//[11¯0] Si(111). On Gd₂O₃/Si(111), Pt is partially crystallized with (111) orientation. There are two epitaxial domains and a slightly visible (111) fiber texture. The in-plane relationships of these Pt(111) domains with Gd₂O₃(111) are a direct one: [11¯0] Pt(111)//[11¯0] Gd₂O₃(111) and a mirror one: [1¯10] Pt(111)//[11¯0] Gd₂O₃(111). XPS reveals that Pt4f exhibits a metallic behavior even for small amounts of Pt but very small chemical shifts suggest that Pt environment is different at the interface with Gd₂O₃. These XPS chemical shifts have been correlated with features in XPD azimuth curves, which could be related with the existence of hexagonal α-PtO₂(0001)layer.