Hideki Sasaoka

Characterization and surface modification of carbon nanowalls

The microstructure and surface features of carbon nanowall (CNW) thin films has been investigated by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). It is found that CNWs have a surface chemical state comprising a mixture of sp2 and a few sp3 bonds. Some oxygen atoms are chemically absorbed on the CNW surface. The valence band XPS spectra revel the CNW shows a band structure like normal crystalline graphite materials. Hydrogen plasma treatment technique is employed to modify the CNW surface, which is evidenced to be an efficient approach to increase CNW surface areas, benefiting to host and anchor catalyst substances.

Fabrication and charaterization of silica nanocoatings on ZnS phosphor particles

With the addition of the cationic surfactant, cetyltrimethylammonium chloride (CTAC), continuous and uniform silica nanocoatings on ZnS phosphors have been successfully obtained. The coatings are proven to cover ZnS phosphors completely by using transmission electron microscopy (TEM), zeta potential and x-ray photoelectron spectroscopy (XPS) analysis. The XPS and Fourier transform infrared red (FT-IR) spectroscopy results provide evidence of the presence of Zn–O–Si bonds between the silica coatings and ZnS phosphors. It is suggested that the bridging effect of CTAC favours the formation of silica coatings, and Zn–O–Si bonds are formed during the annealing procedure.

Characterization of three-dimensional nano-carbon field emission emitters

A unique three-dimensional nano-carbon electron emitter film with high emission current density at low electric field has been developed on stainless steel substrate by a direct current plasma chemical vapor deposition system. Scanning electron microscopy image taken from this film indicates that the film contains cone-like emitters whose array density is about 3×106/cm2. The center of each emitter is a carbon nanoneedle, and many carbon nano-walls are grown from the needle. Transmission electron microscopy observation reveals that the needles are hollow cone shape with bamboo-joint like structures on the side surface. Carbon nano-wall growth just starts from the bamboo joints. Raman spectroscopy was used to evaluate its graphitization degree and crystallinity. The I-V characteristic exhibits an emission current density of 143mA/cm2 at 2.2V/μm, and the field emission current is durable, making it possibly suitable for developing field emission devices.

Fabrication of field emission lamps using nano-crystalline diamond on carbon nanowall films

We have developed the funnel-shaped field emission lamp (FEL), utilizing the cathodoluminescent (CL) light which goes to the inside of the FEL. The electron emitter, arranged along the central axis of the FEL vessel, is comprised of six rod-shaped substrates on which nano-diamond /carbon nanowall (ND/CNW) layer this is the emitting film that emit electrons around the angle of 360°. The electric field on ND/CNW films are corrected by utilizing the bending effect of the electric contour lines surrounding the terminal metal parts of the electron emitter. The changes of the electron densities irradiating on the phosphor layer can be controlled to within 50%. The sealed FEL has been verified to emit homogeneous surface light and it kept the even performance status for more than 11 months.

Nano-carbon field electron emission films synthesized by a confined-plasma chemical vapor deposition system

In this study, we developed a novel plasma CVD system that can generate a uniform long confined plasma column which enables us to grow the thin films on entire surface (3600) of the long-wire or rod substrates. By means of this kind of confined plasma CVD (CPCVD), nano-carbon films have been successfully deposited on the 1000-mm-long metal wires. The as-deposited nano-carbon films present the efficient field electron emission properties.

Development of New Scaife Machine for Making the High Precision Diamond Cutting Tools

We have developed a new scaife polishing machine for the purpose of polishing the high precision diamond cutting tools. As a high precision cutting tool, the high sharpness and flawless cutting edge are required. By using this polishing machine, the sharpness of a diamond tool at the cutting edge can be controlled within the range of 20nm. This machine is equipped with a submicron-scale mirror finished hardened-steel polishing Scaife, a supporting table can reduce the face deflection to less than 1μm, and a plastic diamond tool holder for protecting the edge of the diamond tool from the unexpected shock, which is supported by three points consisting of the edge of diamond tip and two control screws, this structure can help to adjust the work surface to any angles by only adjusting the two control screws. To facilitate the advanced angle operations, the algorithm was created to calculate the overhang length variations of the two control screws for controlling the changes of roll- and pitch-angle of the diamond tools.