Mamoru Kohata

Preparation of cubic boron nitride film by CO2 laser physical vapour deposition with simultaneous nitrogen ion supply

Abstract Hard cubic boron nitride (c-BN) rich films have been prepared by a newly developed CO2 laser physical vapour deposition process assisted by a simultaneous nitrogen ion supply. A high power CO2 laser of 200–1000 W was focused and irradiated onto the peripheral surface of a rotating sintered hexagonal boron nitride (h-BN) ring and the vapour was deposited on a substrate. N2 gas ionized in a Kaufman-type ion source was accelerated at a bias voltage of 0–2.0 kV and irradiated onto the substrate simultaneously with the laser evaporation process. The films were characterized by electron spectroscopy for chemical analysis, thin film X-ray diffraction, Auger electron spectroscopy, IR spectroscopy and scanning electron microscopy. Mechanical properties were also evaluated by Knoop hardness measurements, scratch tests and wear experiments. The composition ratio N:B of the films prepared from high purity 99% h-BN increased as the accelerating voltage increased and neared unity at about 1 kV. Cubic boron nitride (c-BN) was clearly identified at accelerating voltages over 0.5 kV. The higher the accelerating voltage was, the greater was the proportion of the cubic phase. The c-BN-rich films were found to have extremely high Knoop hardness of 3800–4600 kgf mm−2 and sufficient wear resistance against NiMo steel (SAE 4620).

Deposition of amorphous carbon using a shunting arc discharge

Abstract Using the shunting arc discharge, preparation of a hydrogen free diamond-like carbon (DLC) film is demonstrated. The substrate is immersed into the plasma, and a series of pulse voltage is applied to the substrate was synchronized with a generation of the shunting arc with a peak current of 1.7 kA. The prepared film has a smooth surface with a dark blue color, with only droplets even without filtering system. The film is amorphous and a typical Raman spectrum with the D and G band is observed. The film thickness is largest in a voltage range of −4 to −8 kV, from which it is inferred that the carbon ions contribute to the film preparation.

Preparation of aluminum oxide films by ion beam assisted deposition

Abstract Aluminum oxide films were prepared by vapor deposition of aluminum and simultaneous irradiation with oxygen ion beam in the energy range of 2–24 keV with an Al/O transport ratio in the range of 0.5–14. The films were formed on Si(100) wafers and glass substrates fixed on a water-cooled holder. Film characterizations were carried out using X-ray photoelectron spectroscopy (XPS) for elemental composition measurements and chemical bonding states, and by X-ray diffraction (XRD) for film crystallization. The XPS spectra of Al 2p 1/2 obtained from samples with nearly stoichiometric composition (Al/O∼0.67) showed a peak at ∼74 eV corresponding to the AlO chemical bonding state of the γ phase. The XRD patterns of the films prepared with oxygen ion energy of 20–23 keV showed the crystallization of γ-Al 2 O 3 on both Si(100) wafer and glass substrates. Mechanical and optical properties of the films were also presented in correlation with the deposition conditions.

Interfacial structure control of cubic boron nitride films prepared by ion-beam assisted deposition

Abstract Boron nitride films were prepared by ion beam assisted deposition (IBAD). The films were synthesized by depositing boron vapor under simultaneous bombardment with nitrogen ions and nitrogen-argon mixture ions. Cubic boron nitride (c-BN) films with enhanced tribological properties had been explored by inserting a B-rich layer as a controlled buffer at the interface. Tribological characterizations of the buffer layer and the double-layered BN films consisting of the c-BN layer underneath with the B-rich buffer layer have been performed. Successful growth of c-BN layer has been observed on the B-rich layer and the hardness of the films increased almost linearly with increasing fraction of the sp 3 bonded cubic phase in the c-BN layer. The control of the interfacial structure exhibited a significant effect on the improvement of the tribological properties of the films due to the effective relaxation of internal stress of the c-BN films.

Coating and ion implantation to the inner surface of a pipe by metal plasma-based ion implantation and deposition

This article describes the characteristics of the coating of the inner surface of a pipe using plasma-based ion implantation and deposition method with a d.c. titanium-cathodic-arc in nitrogen gas. It was confirmed that the coating of the inner surface of the pipe with titanium nitride film was possible by using this method. The film structure and preferential orientation can be controlled by the applied voltage to the pipe. The film on the inner surface of a pipe in its entrance region showed an oriented columnar grain structure oblique to the substrate. The surface morphology changed with the waveform of the applied voltage. These characteristics were closely related to the dynamic behavior of the ions.

Macroparticles on titanium nitiride thin film prepared by cathodic-arc plasma-based ion implantation and deposition

This article describes particles formed on a substrate when a cathodic arc is generated in nitrogen at pressure of 0.27 Pa for plasma-based ion implantation and deposition (PBII-D). After a titanium nitride (TiN) film was deposited and titanium and nitrogen ions were simultaneously implanted into the silicon substrate, macroparticles of TiN were observed on/in the deposited film. Most of these were less than 1 μm in size and were classified as spherical or non-spherical particles. The spherical particles were so-called droplets, while non-spherical particles were formed by crystal growth from the near-surface of the substrate. The latter was inferred to originate from nucleus precipitation due to the high-energy ion implantation. The number density and the shape of the non-spherical macroparticles changed to a great extent with the applied voltage and its waveform.

Synthesis of aluminum oxide thin films by ion beam and vapor deposition technology

Abstract Aluminum oxide films were prepared by evaporation of aluminum and simultaneous bombardment by oxygen ions in the energy region 2–20 keV with the aluminum/oxygen transport ratio in the range 0.5–10. The films were formed at room temperature on substrates of Si(100) wafers. Infrared absorption spectra indicated that the structure of the films was α-type and/or γ-type, and X-ray photoelectron spectra show that the phase structure was determined by both the Al/O transport ratio and the energy of the oxygen ion beams. As a result of the study of the crystalline growth of the films, the X-ray diffraction pattern of the film prepared by 20 keV oxygen ions and a transport ratio of 2.45 showed a peak due to the γ-Al2O3 crystal.

PROPERTIES OF DEPTH-PROFILE CONTROLLED BORON NITRIDE FILMS PREPARED BY ION-BEAM ASSISTED DEPOSITION

Abstract Boron nitride films were prepared by vapor deposition of boron and simultaneous bombardment with mixed gas ions of nitrogen and argon in the energy range of 0.2 to 20 keV. The films were prepared on various kinds of substrates including silicon wafers, tungsten carbide plates and various ceramic plates at a temperature of 400°C. In the synthesis of the BN films, a boron-rich buffer layer between the substrate and the BN film was formed by energetic nitrogen ion beam bombardment, improving tribological properties such as the depth-profile controlled layer. The buffer layer improved film adhesion, and chemical stability, thermal stability at elevated temperature and corrosion resistance of the BN films also gave good results.

Preparation of TiN film on the inner surface of a pipe by plasma-based ion implantation and deposition

Titanium nitride (TiN) films were prepared on the inner surface of a pipe with a diameter of 80 mm and a length of 150 mm using plasma-based ion implantation and deposition (PBII-D). A titanium cathodic arc discharge was generated at a nitrogen pressure of 8 Pa. Gold-colored TiN films were prepared. The film thickness decreases with increasing the distance from the cathodic arc source due to the spatial distribution of the plasma species. A grounded rod, which is placed in the center of the pipe, does not largely influence the film thickness, but enhances the microhardness of the prepared film. The center rod also makes the PBII-D process stable for applying a pulse voltage.

Effects of target voltage on the structure of the film prepared by plasma-based ion implantation and deposition method

Abstract This article describes the characteristics of titanium nitride film prepared by the plasma-based ion implantation and deposition method using a titanium cathodic arc of d.c. 80 A. The surface morphology and structure of the film were affected by the voltage applied to the target. With increasing the negative voltage, the surface became smoother with a lesser number of particles. The grain structure varied from the stratified one at 0 kV to the columnar one at −5 to −20 kV, and further to the densely packed columnar one at −40 kV. These facts strongly suggested that the ions in the sheath played an important role in the deposition of the film.