Tracking thermally-activated transformations in a nanostructured metal/oxide/metal system

Abstract

We present experimental and theoretical evidence of sequential redox processes and structural transformations occurring by increasing temperature in a metal/oxide/metal system obtained via deposition of Fe atoms onto a z′-TiO_1.25/Pt(111) ultrathin film in UHV. The initial reduction of the z′-TiO_x phase by Fe at room temperature is followed by Fe diffusion and partial penetration into the substrate at intermediate temperatures. This triggers the formation of a bi-component material in which mixed FeO/TiO₂ nanoislands coexist on a h-TiO_1.14 ultrathin film, notably restructured (from rectangular to hexagonal) and reduced (from Ti : O = 1 : 1.25 to 1 : 1.14) with respect to the original TiO_1.25 phase. Further heating recovers the pristine z′-TiO_x phase while Fe completely dissolves into the substrate.