Nobuyuki Kitagawa

Formation of cubic-A1N in TiN/A1N superlattice

Abstract Ceramic superlattice is one of approaches for new ceramic film development. We deposited TiN/A1N superlattice films by arc ion-plating process, and evaluated the crystal structure of these films by transmission electron diffraction and X-ray diffraction. It was revealed that the crystal structure of A1N changes from Wurtzite type to NaCl type for superlattice periods ≤ 3 nm. The film hardness increased to about twice that of the TiN single layer film at a period = 2.5 nm. NaCl phase of A1N is one of the phases that exists under high pressure and it is expected that there will be a high bulk modulus.

Thermal stability of TiN/AlN superlattices

Abstract In this paper, the thermal study of a TiN/AlN superlattice was reported. The thermal stability of a superlattice structure and a crystal structure of cubic AlN in a TiN/AlN superlattice were evaluated by using in situ high temperature transmission electron microscopy (HTTEM), X-ray diffraction (XRD) measurements and TEM observations after an annealing treatment in a hydrogen atmosphere, and semi in situ high temperature X-ray diffraction (HTXRD) in a nitrogen atmosphere. It was confirmed that the superlattice structure remained up to 1473 K for a short time by HTTEM observation. HTXRD studies showed that the superlattice structure and c-AlN remained after 1273 K annealing for 3.5 h. According to the change of low angle diffraction intensity of HTXRD, two kinds of diffusion processes may operate. One was short range diffusion that improved the superlattice structure from 1073–1233 K and the other was long range diffusion that started at above 1233 K.

Deposition of NiTiN nano-composite films by cathodic arc ion-plating

Abstract Thick composite films containing Ni and TiN were prepared by using the filtered cathodic arc ion-plating method. In this study, Ni and Ti were simulataneously evaporated by vacuum arc discharge in a nitrogen atmosphere. Since a magnetic field in a filtered arc-evaporator transports only small size ionized particles to the substrate, macro-particles are eliminated from the film and a uniform fine structure can be obtained. It was observed by transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD) that Ni and TiN particles with 5–10 nm diameter were deposited. Scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX) were also used to investigate the morphology and the composition of films. Residual stresses were evaluated by measuring the bending of the substrate before and after the deposition. Hardness measurements were also carried out to investigate the mechanical properties of films. The hardness of the film increased with the increase in the TiN content of the film. When the Ni content was lower than 30 at%, the hardness of the film was nearly the same as TiN itself. The residual stresses of the Ni rich films were 0.05–0.5 GPa (tensile stresses) and those of the TiN rich films were −1–−3 GPa (compressive stresses). Substrate bias voltage and N 2 pressure had a great effect on the residual stress. The compositionally graded multi-layered films (thickness of 350 μm) were synthesized from these results.

Characterization of ion implanted TiN films

Abstract The tribological properties, chemical states, and microstructures of TiN films implanted with Cr and Al ions have been studied. TiN films were deposited using the cathodic arc ion-plating method. After the deposition, Cr or Al ions were implanted into TiN films at an energy below 200 keV. The wear resistance of the ion implanted TiN films, measured by the pin-on-disk method, was improved when compared to the as-deposited TiN film. The XPS spectrum of the implanted films showed the components of CrN and AlN bonds respectively. The glancing angle X-ray diffraction analysis indicated the formation of a ternary compound of TiCrN or TiAlN. Some mechanisms of the tribological improvements by ion implantation are discussed.