Seiichiro Matsumoto

Diamond synthesis from gas phase in microwave plasma

Crystalline diamond predominantly composed of {100} and {111} faces was grown on a non-diamond substrate from a gaseous mixture of hydrogen and methane under microwave glow discharge conditions.

Vapor Deposition of Diamond Particles from Methane

Microcrystalline diamond has been formed on silicon or molybdenum substrates by vapor deposition from a geseous mixture of methane and hydrogen. Cubo-octahedral or multiply-twinned crystals were obtained. The structure of the deposits was identified by electron diffraction and Raman scattering.

Growth of diamond particles from methane-hydrogen gas

Microcrystals of diamond were grown on non-diamond substrates including silicon, molybdenum and silica, as well as on diamond by chemical vapour deposition. Deposition was carried out by passing a mixture of hydrocarbon and hydrogen gases through a heated reaction chamber in which a hot tungsten filament was held near the substrates. The deposit was identified by reflection electron diffraction and Raman spectroscopy. The effects of experimental conditions on the growth features were studied.

Synthesis of diamond films in a rf induction thermal plasma

Microcrystals and microcrystalline films of diamond were prepared on molybdenum substrates in a thermal plasma which was produced by rf inductive heating in an argon‐hydrogen‐methane mixture gas under 1 atm pressure. The deposition rate amounted to 1 μm/min.

Electron microscopic observation of diamond particles grown from the vapour phase

Diamond particles prepared by chemical vapour deposition from a mixture of methane and hydrogen gases have been examined by electron microscopy. The particles were crystalline with a cubic structure. The typical habit was cubo-octahedron and twinned crystals, i.e. spinel-law twins and multiply-twinned particles, were also observed. Four cage compounds, i.e. bicyclo[2.2.2] octane, tetracyclo[4.4.0.13,9.14,8] dodecane, hexacyclo[5.5.1.12,6.18,12.03,11.05,9]pentadecaneand dodecahedrane are proposed for embryos of twinned crystals.

High-Rate Deposition of High-Quality, Thick Cubic Boron Nitride Films by Bias-Assisted DC Jet Plasma Chemical Vapor Deposition

Cubic boron nitride thin films were deposited on (100) silicon substrates by DC jet plasma chemical vapor deposition in an Ar–N2–BF3–H2 gas system. Negative DC bias was applied on the substrate during deposition. Scanning electron microscopy, x-ray diffraction, infrared and Raman spectroscopy were carried out to characterize the samples. It was found that boron nitride films with cubic phase over 90% were synthesized under optimized conditions. A high deposition rate of about 0.3 µm/min and a film thickness over 3 µm were firstly achieved. Furthermore, the Raman measurements show clear TO and LO characteristic peaks of c-BN with a full width at half maximum of 28.8 and 19.7 cm-1, revealing a high quality of the deposited films.

The introducing of fluorine into the deposition of BN: a successful method to obtain high-quality, thick cBN films with low residual stress

Abstract Cubic boron nitride films were synthesized on silicon substrates by DC-bias-assisted DC jet chemical vapor deposition in an Ar–N 2 –BF 3 –H 2 system. By this method, the deposition of cBN at high gas pressure of 50 torr became possible, and the conditions of cBN CVD approached to those of diamond CVD. cBN films with low residual stress (1–2 GPa) and with large crystal size of up to several hundred nanometers were obtained and clear Raman peaks of cBN appeared. Furthermore, the deposition rate was as high as 0.3 μm/min at the initial stage and over 20-μm-thick BN films were obtained for a 3-h deposition. These remarkable improvements are attributed to the preferential etching effect of fluorine to sp 2 bonds and the decrease of the bombarding energy of ions.

Hardness and Young’s modulus of high-quality cubic boron nitride films grown by chemical vapor deposition

The elastic and mechanical properties of high-quality cubic boron nitride (cBN) films with a few microns thickness and submicron grain size grown on silicon substrates by chemical vapor deposition were determined by measuring the dispersion of surface acoustic waves propagating along the surface of the layered system. The values are compared with those obtained with an ultralow load indenter (Triboscope). Specifically, the hardness, Young’s modulus and density of the film were measured.

High-quality, faceted cubic boron nitride films grown by chemical vapor deposition

Thick cubic boron nitride (cBN) films showing clear crystal facets were achieved by chemical vapor deposition. The films show the highest crystallinity of cBN films ever achieved from gas phase. Clear evidence for the growth via a chemical route is obtained. A growth mechanism is suggested, in which fluorine preferentially etches hBN and stabilizes the cBN surface. Ion bombardment of proper energy activates the cBN surface bonded with fluorine so as to enhance the bonding probability of nitrogen-containing species on the F-stabilized B (111) surface.

Electron field emission from nanostructured cubic boron nitride islands

Nanocrystal-assembled cubic boron nitride (cBN) islands are formed by using low-energy (∼20eV) ion irradiation in an inductively coupled fluorine-containing plasma. The temporal evolution of surface morphology and roughness reveals three-dimensional island growth for initial sp2-bonded BN and subsequent cBN, accompanied by a high frequency of renucleation. The formation of cBN islands enhances the field emission and reduces the turn-on field down to around 9V∕μm due to an increase in the island-related field. The results demonstrate the high potential of cBN for field emitters, comparable to other wide band gap semiconductors.