Nobuki Yamashita

Formation of cBN films by ion beam assisted deposition

Boron nitride films were deposited by using ion beams of nitrogen mixed with argon and simultaneous evaporation of boron. The effect of deposition conditions on the formation of the cBN phase were also studied. The acceleration voltage of ions was in the range of 0.3–7 kV. The deposited films were analyzed by infrared absorption spectra, x‐ray diffraction, and transmission electron diffraction. The infrared absorption spectra showed a strong absorption at 1080 cm−1, indicating a formation of the cBN film. It seemed that the amount of the cBN phase in deposited films largely increases with decreases in acceleration voltage, and that the use of ion beams of nitrogen mixed with argon is effective for the formation of the cBN phase. Deposited films exhibited electron diffraction rings with interplanar spacings that agreed well with the values of cBN having a zinc blende structure. Deposited films also exhibited x‐ray diffraction patterns that agreed with the (111) plane of cBN. The micro Vickers hardness of t...

Cross-sectional transmission electron microscopy observations of c-BN films deposited on Si by ion-beam-assisted deposition

Abstract Cubic boron nitride (c-BN) films were deposited on Si wafers by ion-beam assisted deposition (IBAD). Both the structure of the film and the interface between the film and the substrate were investigated by cross-sectional transmission electron microscopy (TEM). Two types of specimens were observed. One was formed by IBAD which was performed by irradiating nitrogen with argon ions accelerated to an energy of 0.5 keV and evaporating boron simultaneously. The other was also formed by IBAD under the same conditions as above but employing ion beam dynamic mixing (IBDM), which was performed by irradiating the sample with ions accelerated to a rather high energy of 7 keV and evaporating boron simultaneously. The formation of c-BN was observed in both specimens by electron diffraction patterns and high resolution electron micrographs. The TEM observation clearly showed that the interface between the film and the substrate was different with or without IBDM. The interface of the speicimen formed with IBDM was diffuse, while that of the specimen formed without IBDM was sharp. The formation of the diffuse interface is thought to improve the adhesion of the film.

Fundamental research on the deposition of cubic boron nitride films on curved substrates by ion-beam-assisted vapor deposition

Abstract As fundamental research to deposit cubic boron nitride (BN) films on curved substrates by the ion-beam-assisted vapor deposition method using boron deposition and the irradiation of nitrogen and argon ions, BN films were deposited on Si substrates by waving them and continuously changing the angle of ion irradiation. As a result, it has become clear that cubic BN films are deposited even when the waving angle is ±90°, and that the cubic BN films are deposited on curved substrate surfaces when the substrates are rotated or waved.

Adhesion and structure of c-BN films produced by ion-beam-assisted deposition

Abstract Ion beam dynamic mixing was performed to improve the adhesion of cubic boron nitride (c-BN) films prepared by ion-beam-assisted deposition. The interface between the c-BN film and the substrate and the adhesion of prepared films were also studied. Ion beam dynamic mixing was performed on silicon wafers and WC-Co coated with TiN by irradiation by ions with energies of 3 and 7 keV and by simultaneous evaporation of boron. c-BN films were then deposited by irradiation by ions with an energy of 0.5 keV. The structure and the adhesion of the coatings were studied by IR absorption spectroscopy, X-ray diffraction, Auger electron spectroscopy, scratch tests and cutting tests. The adhesion of c-BN films was greatly improved by ion beam dynamic mixing. The critical load determined from scratch tests becomes larger with increasing ion beam energy. No cohesive failures of films prepared by ion beam dynamic mixing with an ion beam energy of 7 keV were observed in cutting tests on carbon steels.

Compositions in layers modified by ion beam dynamic mixing to improve the adhesion of cBN films and in situ ion measurement

Abstract The depth profiles of elements in layers modified by ion beam dynamic mixing (IBDM) on substrates which unproved the adhesion of cubic boron nitride (cBN) films were studied by Auger electron spectroscopy (AES). The measurements of mass spectra and energy distribution of ions during IBDM were also undertaken in order to monitor the surface composition of the modified layer. The IBDM was performed on WC-Co coated with TiN by irradiation of ions of nitrogen mixed with argon with an energy of 7 keV and simultaneous evaporation of boron. Only a mixed layer, composed of a gradient mixture of boron, nitrogen and the elements of the substrate, was formed on the substrate under a suitable boron/ion arrival ratio. However, the mixed layer was covered by a boron-rich layer whose B/N atomic ratio was in excess of the stoichiometric value of unity with increases in the boron/ion arrival ratio. In situ measurement of boron and titanium secondary ions from the surface of the modified layer, and boron vapor and atmosphere gases ionized by the ion beam, were possible during IBDM. The changes of the intensity ratio with operating time of secondary ions of titanium to those of boron, correlated well with the depth profiles of the titanium composition by AES.