Toshiya Watanabe

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.

The growth of (TbxGd1 − x)AlO3 single crystals by the Czochralski method

(Tb x Gd 1-x )AlO 3 single crystals were grown by the Czochralski method. The crystals grown from Tb-rich melts under a reducing atmosphere were both twin and crack free. It is generally difficult to grow single crystals without cracks from Gd-rich melts. The optical properties of the crystals could be controlled by substituting Gd for Tb.

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.