Masami Ishikawa

Manganese Oxide Thin Film Preparation by Potentiostatic Electrolyses and Electrochromism

Manganese oxide (MnO x ) thin films were deposited on transparent conducting tin oxide glass substrates by potentiostatic anodic electrolysis of alkaline solution of a manganese ammine complex at 298 K. The effects of varying deposition potentials on the microstructure and the electrochromic (EC) properties of the films were investigated, Characterization of films by X-ray diffraction revealed that two distinct potential regions (lower and higher than 0.3 V vs. Ag/AgCl) were available for the film deposition; the crystal structure of the film deposited at lower and higher regions were γ-Mn 2 O 3 and/or Mn 3 O 4 and Mn 7 O 13 .5H 2 O, respectively. X-ray photoelectron spectroscopy (XPS) analyses of the films featuring exchange splitting effect on Mn 3s spectra indicated that the valence of manganese in the films prepared at lower and higher potential regions are mixtures of divalence-trivalence and of trivalence-tetravalence, respectively The XPS analysis also revealed that terminal chemical bonding species of the films are a mixture of hydroxide (Mn-O-H) and oxide (Mn-O-Mn). The mechanism of the EC process, by which the color change between brown and light yellow occurs, could be explained in terms of the transformation between these two oxygen groups in Mn-O-H and Mn-O-Mn, accompanied by the change in valence of Mn. The EC durability of the films in switching performance was also assessed.

Preparation of Manganese Oxide Thin Films by Electrolysis/Chemical Deposition and Electrochromism

Manganese oxide (MnO 3 ) thin films were deposited onto transparent and conductive tin oxide-coated glass substrates by electrochemical deposition (at 1.2 V vs. Ag/AgCl) and subsequent chemical [electrolysis/chemical (EL/C)] processing in a manganese ammine complex solution at pH 8. Characterization by X-ray diffraction (XRD) of the films revealed that the crystal structure formed in the films by EL/C deposition is assigned to γ-Mn 2 O 3 and/or Mn 3 O 3 . X-ray photoelectron spectroscopy (XPS) was also performed to focus on exchange splitting effect shown in Mn 3s spectra and peak analyses of O Is spectra of the films. From electrochemical, quartz crystal microbalance, XRD, XPS, and atomic force microseope studies, a mechanism of film growth was illustrated, featuring time course of rest potential during chemical process. The XPS data also suggested that the electrochromic behavior, turning brown and light yellow by the anodic and cathodic polarization in potassium borate buffer solution at pH 10. originates from a transformation between two oxygen groups in hydroxide (Mn-O-H) and oxide (Mn-O-Mn) accompanied by the change in valence of Mn. The repeated EC switching performance of the films was also assayed.

XRD and XPS characterization of electrochromic nickel oxide thin films prepared by electrolysis–chemical deposition

Electrochromic (EC) behaviours of nickel oxide (NiOx) thin films, grown by chemical process in a nickel ammine complex solution [Ni(NH3)x2+] after electrolysis of this solution (EL–C method), were investigated using various alkaline electrolyte solutions; potassium borate buffer (pH 12), KOH (pH 12.9), (CH3)4NOH and (C2H5)4NOH. The fully oxidized films in all adopted electrolytes commonly showed broadened UV–VIS spectra in the visible and near IR region. However, voltammetry studies associated with photoabsorption of the films revealed an apparent difference in the EC dynamics among the electrolytes caused by the variation of cation sizes and electrolyte solution pH. Characterization of as-prepared, oxidized and reduced films in the electrolytes by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were performed to explain the mechanism of the films based on the conversion between layered α-Ni(OH)2 and γ2-2NiO2·NiOOH. A model according to the extraction/insertion of cations or water molecules from/into the interlayer was proposed.

Effect of some factors on electrodeposition of nickel-copper alloy from pyrophosphate-tetraborate bath

Effects of bath compositions and operating conditions on the electrodeposition of nickel-copper alloy from a pyrophosphate-tetraborate bath have been studied. The composition of nickel-copper alloy was influenced by pyrophosphate concentration, pH of the bath, metal ion ratio and citrate ions in the bath. Pyrophosphate ions facilitate the codeposition of nickel and copper, but their excess inhibits the nickel deposition. The nickel deposition was also inhibited by increasing the concentration of copper and citrate ions.

Preparation of thin film resistors with low resistivity and low TCR by heat treatment of multilayered Cu/Ni deposits

Abstract Thin Cu–Ni alloy film resistors were prepared by different methods using both electroless plating and electrodeposition. Alloy composition, structure and electrical properties (resistivity and TCR) were examined as a function of plating conditions. Low resistivity and low TCR performance were achieved by heating the multilayered Cu/Ni film deposited on electroless Cu.

Electrochromic properties of nickel oxide thin films prepared by electrolysis followed by chemical deposition

Abstract Nickel oxide (NiOx) thin films were prepared onto transparent conductive tin oxide (NESA) substrates by chemical process in a nickel ammine complex solution following electrochemical deposition (at 1.1 V vs Ag AgCl ) from this solution. Compared with the NiOx films prepared simply by anodic deposition, the films obtained through the chemical process showed different mode of electrochromism between colorless and dark brown in a sodium borate buffer solution at pH 12; the absorption spectrum of the composite film in the colored (oxidized) state was broadened in the visible and near infrared region. Characterization of the films revealed that crystal structure of the film deposited during chemical process is assigned to α-Ni(OH)2, and that its electrochromism is based on the reversible oxidation of γ2-2NiO2 · NiOOH structure. Electrochromic switching performance of the film was investigated.

EFFECT OF TETRABORATE IONS ON ELECTRODEPOSITION OF NICKEL-COPPER ALLOY FROM A PYROPHOSPHATE BATH

Abstract Effect of tetraborate ions on NiCu alloy electrodeposited from a pyrophosphate bath has been studied. Deposits from a tetraborate-free bath were non-uniform, blackish and contaminated with insoluble compounds, which was confirmed to be nickel hydroxide hydrate by X-ray diffraction and X-ray photoelectron spectroscopic analysis. In contrast, the deposits from a bath containing sodium tetraborate were smooth, fine-grained, nickel-rich and gave nickel-like lustrous appearance. Sodium tetraborate was found to improve the quality of NiCu alloy deposits by preventing the increase of pH at electrode/electrolyte interface and the precipitation of the insoluble nickel hydroxides.

Preparation of silica thin films by electrolyses of aqueous solution

Silica thin films were first deposited on a copper substrate by potentiostatic cathodic electrolysis of a solution of ammonium hexafluorosilicate at 298 K. The film deposition according to the reduction of H + was monitored by a quartz crystal microbalance and measured by X-ray fluorescence spectrometry. Characterization of the films by X-ray photoelectron spectroscopy, infrared reflection-absorption spectroscopy, and scanning electron microscopy revealed that the film mainly consisted of SiO 2 with silanol groups covering the surface. Basic reactions for film deposition are proposed including a pH-shift triggered by H 2 evolution.

Preparation and Electrical Resistance Characteristics of Electroless Copper-Nickel Alloy Deposits

SummaryStudies have been made of an electroless copper-nickel-phosphorus alloy from a citrate complex bath using hypophosphite as reducing agent and electroless copper-nickel binary alloy from a triethanolamine complex bath using formaldehyde as reducing agent. With an increase in copper content of alloy, the specific resistance of deposit decreased. The TCR of copper-nickel-phosphorus alloy increased remarkably because of the crystallization of Ni3P after heat treatment. But the increase in TCR of copper-nickel binary alloy was moderate and not so striking as for the phosphorus containing alloy.

Preparation of Silica Thin Films by Reduction of Aqueous Solution

Silica thin films were first deposited on a poly(ethylene terephthalate) sheet and silicon wafer substrates by the reduction of an aqueous ammonium hexafluorosilicate solution by dimethylamine borane at 323 K. The time course of film growth was measured by X-ray fluorescent (XRF) spectrometry and an enhancement of deposition rate by coating the substrates with catalyst was observed. Characterization of films by X-ray photoelectron spectroscopy (XPS) and infrared (IR) absorption spectroscopy proved that the film consisted mainly of SiO 2 and a surface hydroxyl group. Reactions for film deposition focused on pH shift by reduction of the solution were proposed.