Ruriko Hatada

Synthesis and properties of TiO2 thin films by plasma source ion implantation

Plasma source ion implantation was used to prepare anatase type photocatalytic TiO2 films on silicon wafer and quartz glass from titanium tetraisopropoxide as a precursor. RF power was used to produce a glow discharge plasma. High negative voltage pulses of −20 kV, repetition rate 100 Hz and 1 kHz were applied to the substrate holder to accelerate ions from the plasma. After the deposition, the films were annealed for 1 h in air at a constant temperature from 673 to 1023 K. The films were analyzed by XRD, XPS and Raman spectroscopy. The photocatalytic property of TiO2 films was evaluated by examining the decomposition of an aqueous solution of methylene blue under UV irradiation. XPS and Raman results showed that the deposited films consisted of Ti, O and C and an amorphous carbon structure. The color of the films changed from black to colorless and transparent after annealing at a temperature above 723 K. XPS results showed that the composition of the films annealed at 873 K was stoichiometric TiO2. The formation of a single phase anatase type TiO2 crystalline was confirmed for the films annealed between 723 and 923 K by XRD and Raman measurements. The films annealed at 973 K were a mixture of anatase and rutile type crystals. The film annealed at 973 K had the highest photocatalytic activity for the decomposition of aqueous solution of methylene blue.

Deposition and characterization of Ti- and W-containing diamond-like carbon films by plasma source ion implantation

Abstract Ti and W-containing diamond-like carbon (DLC) films were prepared on silicon wafer substrate by a process combining reactive magnetron sputtering with plasma source ion implantation (PSII). Ti and W were deposited by r.f. magnetron sputtering of a metal target and PSII using hydrocarbon gas. Ar/C 2 H 2 mixed gas was introduced into the discharge chamber. The negative high voltage pulse (−10 kV, 100 Hz, 100 μs) superposed on a d.c. voltage of −0.5 kV was applied to the substrate holder. The structure of the films changed from metal containing amorphous DLC, to a composite of metal containing DLC and metal carbides with increasing metal content in the films. The sheet resistivity of the films was decreased abruptly with increasing metal content in the films. The tribological properties of the films were improved by W doping.

Preparation and properties of nitrogen and titanium oxide incorporated diamond-like carbon films by plasma source ion implantation

Abstract Nitrogen and titanium oxide incorporated diamond-like carbon (DLC) films were deposited by a plasma source ion implantation on silicon wafer and quartz glass. Pure acetylene gas was used as a working gas for plasma. Additional nitrogen and titanium tetraisopropoxide gases were fed into acetylene plasma to prepare nitrogen and titanium oxide incorporated DLC films. The plasma was generated by a radio frequency glow discharge. Ions were accelerated from the plasma by a high-voltage pulse (−20 kV, 100 Hz, 50 μs) applied directly to the substrates. The surface morphology was observed by a scanning electron microscope (SEM) and an atomic force microscope (AFM). The compositional and structural characterization of the films was carried out using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The hardness of the films was measured by an indentation method. The sheet resistivity of the films was measured by a four-point probe method. The results showed that all of the N incorporated and unincorporated films were amorphous and showed typical Raman spectra of DLC films. The XPS and the FT-IR spectra indicated the formation of C–N, CN and CN valence bonds. XPS measurement for titanium oxide incorporated films revealed the existence of Ti–C, Ti–O, C–C bonding in the DLC films. The hardness of the nitrogen and titanium oxide incorporated films decreased with the amount of incorporated species. The sheet resistivity of the films decreased abruptly with increasing nitrogen and titanium oxide contents in the films.

Preparation and Properties of Ag-Containing Diamond-Like Carbon Films by Magnetron Plasma Source Ion Implantation

The doping effect of silver on the structure and properties of diamond-like carbon (DLC) films was investigated. The samples were prepared by a process combining acetylene plasma source ion implantation (high-voltage pulses of −10 kV) with reactive magnetron sputtering of an Ag disc. A mixture of two gases, argon, and acetylene was introduced into the discharge chamber as working gas for plasma formation. A negative high-voltage pulse was applied to the substrate holder, thus, accelerating ions towards the substrate. The chemical composition of the deposited films was modified by the respective gas flows and determined using X-ray photoelectron spectroscopy and secondary ion mass spectrometry. The silver concentration within the DLC films influenced the structure and the tribological properties. The surface roughness, as observed by scanning electron microscopy, increased with silver concentration. The film structure was characterized by Raman spectroscopy and X-ray diffractometry (XRD). The DLC films were mainly amorphous, containing crystalline silver, with the amount of silver depending on the process conditions. The tribological properties of the films were improved by the silver doping. The lowest friction coefficient of around 0.06 was derived at a low silver content.

Ion implantation into inner wall surface of millimeter size diameter steel tube by plasma source ion implantation

Abstract Nitrogen and carbon ions were implanted into the inner wall surface of 304 austenitic type stainless steel and Ni tubes with inner diameters of 0.9, 2 and 1.6 mm, by a plasma source ion implantation (PSII). These 30 mm long substrate tubes were fixed to an alumina ceramic tube in a vacuum chamber, fed with nitrogen and acetylene gases. A 2.45 GHz microwave was supplied to an antenna in the alumina ceramic tube and plasma was produced by a coaxial electron cyclotron resonance (ECR) discharge in this tube. A negative high voltage pulse of 15 kV (1 kHz, 10 μs) was applied to the steel and Ni tubes to extract ions from the generated plasma. The compositional and structural characterizations of the implanted surfaces were carried out using Auger electron spectroscopy and Raman spectroscopy. The results showed that uniform nitrogen ion implantation into the millimeter size inner wall surface of metal tubes was achieved by the PSII. Carbon implantation and subsequent diamond like carbon (DLC) coating was confirmed for the inner wall surface treated by acetylene PSII.

Thin sol-gel-derived silica coatings on dental pure titanium casting.

The sol-gel dipping process, in which liquid silicon alkoxide is transformed into a solid silicon-oxygen network, can produce a thin film coating of silica (SiO(2)). The features of this method are high homogeneity and purity of the thin SiO(2) film and a low sinter temperature, which are important in the preparation of coating films that can protect metallic ion release from the metal substrate and prevent attachment of dental plaque. We evaluated the surface properties of dental pure titanium casting coated with a thin SiO(2) or SiO(2)/F-hybrid film by the sol-gel dipping process. The metal specimens were pretreated by dipping in isopropylalcohol solution containing 10 wt% 3-aminopropyl trimethoxysilane and treated by dipping in the silica precursor solution for 5 min, withdrawal at a speed of 2 mm/min, air-drying for 20 min at room temperature, heating at 120 degrees C for 20 min, and then storing at room temperature. Both SiO(2) and SiO(2)/F films bonded strongly (above 55 MPa) to pure titanium substrate by a tensile test. SiO(2(-)) and SiO(2)/F-coated specimens immersed in 1 wt% of lactic acid solution for two weeks showed significantly less release of titanium ions (30. 5 ppb/cm(2) and 9.5 ppb/cm(2), respectively) from the substrate than noncoated specimens (235.2 ppb/cm(2)). Hydrophobilization of SiO(2(-)) and SiO(2)/F-coated surfaces resulted in significant increases of contact angle of water (81.6 degrees and 105.7 degrees, respectively) compared with noncoated metal specimens (62.1 degrees ). The formation of both thin SiO(2) and SiO(2)/F-hybrid films by the sol-gel dipping process on the surface of dental pure titanium casting may be useful clinically in enhancing the bond strength of dental resin cements to titanium, preventing titanium ions release from the substrate, and reducing the accumulation of dental plaque attaching to intraoral dental restorations.

Temperature dependent properties of silicon containing diamondlike carbon films prepared by plasma source ion implantation

Silicon containing diamondlike carbon (Si-DLC) films were prepared on silicon wafer substrates by a plasma source ion implantation method with negative pulses superposed on a negative dc voltage. A mixture of acetylene and tetramethylsilane gas was introduced into the discharge chamber as working gases for plasma formation. Ions produced in the plasma are accelerated toward a substrate holder because of the negative voltage applied directly to it. After deposition, the films were annealed for 0.5 h in ambient air at temperatures up to 923 K in order to evaluate the thermal stability of the Si-DLC films. The films were analyzed by x-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy, and Raman spectroscopy. The surface morphology of the films and the film thickness were observed by atomic force microscopy and scanning electron microscopy. The mechanical and tribological properties were investigated by an indentation method and a ball-on-disk test. The results show the si...

Silicon carbide and amorphous carbon film formation by plasma immersion ion implantation: a comparison of methane and toluene as plasma forming gases

In the present study a comparison of two different hydrocarbon precursor gases, namely methane and toluene, on the formation of silicon carbide (SiC) and amorphous carbon (a-C:H) films by plasma immersion ion implantation (PIII) of silicon is made. The samples are analyzed by using Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS) for their element composition. XPS and Raman spectroscopy are applied to determine the bonding of silicon and carbon. Depending on the number of high voltage pulses the samples have been treated with, which corresponds to the ion fluence, it is possible to form stoichiometric SiC films without C layers on top of the wafers if methane is used as plasma forming species. For the same process conditions, CH4 PIII always results in thicker SiC and thinner a-C:H films compared with C7H8 PIII. SiC bond formation is proven by XPS. Raman spectroscopy shows the formation of a-C:H films for high pulse numbers for the case of a methane plasma, but already for small pulse numbers if toluene is used for plasma forming species.

The effects of Ti implantation on corrosion and adhesion of TiN coated stainless steel

Abstract Thin titanium nitride (TiN) films of 40 and 70 nm in thickness were deposited on austenitic-type 304 stainless steel substrates by a rf ion plating process, and these specimens were irradiated with 70 kV titanium ions at a fluence of 1 × 10 17 /cm 2 by use of MEVVA IV metallic ion source at room temperature. After that TiN films of 2 μm were deposited by the same method. The results of X-ray photoelectron spectroscopy and Auger electron spectroscopy revealed that implanted titanium penetrated into the substrate and interfacial mixing was verified. The adhesion strength was estimated by a scratch test. It was found that ion implantation can enhance the adhesion strength between the film and the substrate. The corrosion resistance of the specimens was evaluated in aqueous solutions of sulfuric acid by an electrochemical method. Titanium implantation was extremely effective in suppressing the anodic dissolution of stainless steel.

Synthesis and corrosion properties of silicon nitride films by ion beam assisted deposition

Abstract Silicon nitride films SiNx were deposited on 316L austenitic stainless steel substrates by silicon evaporation and simultaneous nitrogen ion irradiation with an acceleration voltage of 2 kV. In order to study the influence of the nitrogen content on changes in stoichiometry, structure, morphology, thermal oxidation behaviour and corrosion behaviour, the atom to ion transport ratio was systematically varied. The changes of binding states and the stoichiometry were evaluated with XPS and AES analysis. A maximum nitrogen content was reached with a Si N transport ratio lower than 2. The films are chemically inert when exposed to laboratory atmosphere up to a temperature of more than 1000°C. XRD and SEM measurements show amorphous and featureless films for transport ratios Si N from 1 up to 10. The variation of the corrosion behaviour of coated stainless steel substrates in sulphuric acid and hydrochloric acid shows a minimum at medium transport ratios. This goes parallel with changes in porosity and adhesion. Additional investigations showed that titanium implantation as an intermediate step improves the corrosion resistance considerably.