Formation and decomposition of gold oxides prepared by an oxygen-dc glow discharge from gold films and studied by X-ray photoelectron spectroscopy

Reaction Monitoring of Gold Oxides Prepared by an Oxygen-dc Glow Discharge from Gold Films in Various Aqueous Solutions by a Surface Plasmon Resonance-based Optical Waveguide Sensing System and X-ray Photoelectron Spectroscopy

“…The gold oxide layers on 50-nm-thick gold films were prepared by vacuum deposition of gold (>99.99%, Tanaka Kikinzoku Kogyo, Tokyo, Japan) on cleaved mica substrates (dimensions: 9 mm × 18 mm × 0.1 mm; Nisshin EM, Tokyo, Japan) followed by an oxygen-dc glow discharge at room temperature under high vacuum (<6.7×10 −4 Pa) conditions. 31,32 A calibrated thickness monitor (XTM/2, Leybold Inficon, East Syracuse, NY, USA) was used to measure both the deposition rate and the gold film thickness. An oxygen-dc glow discharge (10 Pa, 5 mA, 10 min) from a high-purity oxygen (>99.999%, Japan Fine Products, Kawasaki, Japan) flow in a vacuum evaporator that was equipped with a negatively-biased (to approximately 400 V) aluminum electrode was then used to oxidize the gold films.…”

“…Components I and II have both been assigned to hydroxyl groups and are stable up to 500°C, but differ only in the vertical position. 31,32 The angular dependence of the XPS spectra of the gold oxides indicated that the oxygen species of components I and II are present in this order from the top surface of the gold oxide (component III).…”

“…Gold oxide layers with thicknesses of less than 1 nm were prepared by an oxygen-dc glow discharge over various periods (0.5-10 min) from gold films at room temperature and were characterized by XPS in our previous papers. 31,32 A schematic representation of the formation and decomposition of a gold oxide layer with a thickness of approximately 0.6 nm prepared by an oxygen-dc glow discharge (10 Pa, 5 mA, 10 min) from a gold film is shown in Fig. 1.…”

Characterization of Gold Oxides Prepared by an Oxygen-dc Glow Discharge from Gold Films Using a Gold Discharge Ring by X-ray Photoelectron Spectroscopy

“…The formation and decomposition of gold oxide layers with thicknesses ranging from 0.16-0.65 nm prepared from a gold film by an oxygen-dc glow discharge (10 Pa, 5 mA, 0.17-10 min) using an aluminum discharge ring at room temperature were investigated by X-ray photoelectron spectroscopy (XPS) in our previous papers. 27 The O 1s spectra showed four oxygen species, comprising components I, II, III, and IV. Components I and II were both assigned to hydroxyl groups.…”

“…These findings indicated that gold oxide decomposition is accelerated via a reaction with excited water molecules produced by absorption of UV light. 27 The gold oxides decomposed after 6 h in water but decomposed more slowly in hydrocarbons (hexane, octane, and dodecane) at room temperature in a dark atmosphere. 28 The gold oxide was preserved in the oxidized state for 84 d in anhydrous dodecane.…”