Harushige Tsubakino

Hard DLC film formation by gas cluster ion beam assisted deposition

Abstract Diamond-like carbon (DLC) films with high hardness were formed by Ar cluster ion beam assisted deposition at room temperature, using C 60 as a carbon source. The gas cluster ion beam (GCIB) assisted deposition was useful to form hard DLC films, as the bombardments induced high-pressure and high-temperature effects at the impact surface, and ultra low energy effects. When the acceleration energy of Ar cluster ion was 5 keV, the hardness of 50 GPa was obtained. This value was approximately two times higher than that of the films deposited with conventional methods. Wear-resistance properties were also higher than that of conventional films. Rough estimations of sp 2 orbital in the films were carried out with Raman spectra, the films formed with Ar cluster ion bombardment had lower sp 2 contents, which meant films had low fraction of graphite bonding. Thus DLC films exhibiting higher physical characteristics and lower graphite bonding were obtained with GCIB assisted deposition.

NEXAFS study on substrate temperature dependence of DLC films formed by Ar cluster ion beam assisted deposition

Abstract For the optimization of the synthesis condition of the production of diamond-like carbon (DLC) thin films by Ar gas cluster ion beam (GCIB) assisted deposition of fullerene, the local structure of DLC thin films was investigated by measuring near-edge X-ray absorption fine structure spectra of the carbon K-edge over the excitation energy range 275–320 eV, using synchrotron radiation. The DLC thin films were formed by GCIB assisted deposition at substrate temperatures ranging from room temperature to 250 °C. The sp2 content estimated from the analysis of the peak corresponding to the transition of the excitation electron from a carbon 1s orbital to a π* orbital was found to increase with the substrate temperature during GCIB assisted deposition.

Metal surface swelling by heavy charged particle irradiation

Abstract Austenitic stainless steel specimens of Type 316SS were irradiated with 200 keV He+ or N+ ions, and the irradiated specimen surfaces were observed by atomic force microscopy (AFM). At the ion irradiation in high temperatures the specimens show surface step-up. In case of He+, the surface swelling is remarkable and increases linearly with He ion fluence, which indicates the swelling is due to formation of He bubbles. The irradiated surface is sometimes in irregularity, especially at and near grain boundary, remarkable ridging is observed. In case of N+, the surface step-up is less remarkable compared with He+. The swelling shows a so-called bi-linear behavior, i.e. a threshold of N+ fluence appears and beyond the threshold the swelling increase is almost linearly presumably due to evolution of voids induced by the N+ irradiation in high temperature. Denudation of void formation adjacent to grain boundary is recognized.

Effects of ion-implantation with nitrogen ion on microstructures in deformed iron

The implantation with nitrogen ions accelerated at 150 kV has been performed on sheets of high purity iron (99.99%) annealed for 1.8 ks at 773 K and/or cold-rolled with 90% reduction. Dose of the ions was changed in the range of 8 × 1018 to 4 × 1020 N2+/m2. Hardness increased for a wide range in depth and its increments is large in the deformed specimen compared with the annealed and implanted specimen. Iron nitride, Fe16N2 (α″), is formed in both the deformed and the annealed specimens, and the size of α″ particle in the former is smaller than that in the latter. The formation of α″ in the deformed specimen is accompanied by the disappearance of dislocation substructures.

Difference of Irradiation Effects between Ar Cluster Ion and Ar+ for DLC film formation

In order to study the influences of Ar monomer ion (Ar+) on carbon film properties induced by ion beams assisted deposition, Ar cluster ion, Ar+, and their mixed ions (Ar cluster ion and Ar+) irradiated surface during evaporation and deposition of C60. From Near Edge X‐ray Absorption Fine Structure (NEXAFS) and Raman spectroscopy measurements, lower sp2 content in carbon films was obtained via Ar cluster ion beam bombardment in comparison with bombardment by Ar+ and mixed ion beams. Furthermore higher hardness and smoothness of surface were demonstrated via Ar cluster ion bombardments. Thus, it was important to irradiate using higher fraction Ar cluster ions in the beam, in order to obtain hard DLC films with flat surface.

COMPARISON OF IRRADIATION EFFECTS BETWEEN CLUSTER AND MONOMER FOR DLC FILM DEPOSITION

Diamond-like carbon (DLC) films were formed by Ar cluster ion beam assisted vapor deposition of C 60 . To study the effects of contaminating Ar monomer ions (Ar + ) in the cluster beam on the sp 2 content, hardness, and surface morphology of the films, beams of Ar cluster ions, Ar + , and a mixture of cluster ions and Ar + were used From the near edge X-ray absorption fine structure (NEXAFS), lower sp 2 contents in films were obtained when Ar cluster ion beams were used Higher hardness and smoother surfaces were also obtained by irradiations of Ar cluster ion with higher fraction

NEXAFS study on the local structures of DLC thin films formed by Ar cluster ion beam assisted deposition

Near‐edge X‐ray absorption fine structure (NEXAFS) spectra were measured for the optimization of synthesis conditions on the production of diamond‐like carbon (DLC) thin films by the Ar gas cluster ion beam (GCIB) assisted deposition of fullerene. The sp2 contents of DLC films were estimated from the analysis of the peak corresponding to the transition of the excitation electron from a carbon 1s orbital to a π* orbital in the NEXAFS spectrum of the carbon K‐edge over the excitation energy range 275–320 eV. Substrate temperature and Ar cluster ion acceleration voltage in the synthesis conditions of DLC films were optimized to make the sp2 content minimum.