Plasma-produced ultra-thin platinum-oxide films for nanoelectronics: physical characterization

We present a detailed experimental characterization of ultra-thin platinum-oxide films formed on metallic Pt surfaces using O₂ plasma treatment. A monotonic consumption of the metallic Pt by the O₂ plasma is demonstrated by electrical resistance measurements of micron-wide, ultra-thin metallic Pt wires for the range of O₂ plasma exposure times explored in this study. Conversely, angle-resolved X-ray photoelectron spectroscopy (AR-XPS) of the plasma-treated Pt reveals that the oxide layer formed on the Pt surface maintains a constant thickness over these exposure times. In combination, these data demonstrate that the O₂ plasma treatment of Pt simultaneously forms and etches an ultra-thin platinum-oxide layer on the Pt surface. In addition, the AR-XPS data also reveals the oxide layer to be composed of two different platinum–oxygen compounds. Detailed analysis demonstrates a stratified structure for the ultra-thin platinum oxide, with the oxide bulk being composed of PtO₂, likely with PtO defects, and the exposed oxide surface being Pt(OH)_y2 terminated after exposure to ambient conditions. The potential utility of using plasma oxidization to form ultra-thin platinum (or other metal) oxide films on nanoscale metal structures for nano- and molecular-electronic applications is discussed, along with other promising applications in technologies such as sensors and catalysts. PACS 61.43.Dq; 68.47.Gh; 68.55.Ac; 68.55.Jk; 73.50.Bk; 73.61.At; 73.63.Nm; 79.60.Dp