Osamu Tsuda

Synthesis of amorphous carbon films by plasma-based ion implantation using ECR plasma with a mirror field

Abstract Carbon films were synthesized on Si wafer with or without a pulse biasing and DC biasing by a plasma-based ion implantation system using an electron cyclotron resonance (ECR) plasma source with a mirror field and a power supply to apply negative high-voltage pulses and a negative DC bias to the substrate. Diamond-like carbon (DLC) films with a smooth surface and a low friction coefficient could be formed by the application of low negative-voltage pulses to the substrate, such as −2 kV; however, polymer-like carbon films were formed without pulse biasing or by only a DC biasing to the substrate. Furthermore, the tribological properties, such as friction coefficient and wear, were much improved under a high applied load during the friction test when the DLC film was formed by the simultaneous application of the pulse bias of −2 kV and the DC bias of −200 V. It is considered that the improvement in tribological properties was due to the increase in thickness of the mixed layer formed at the interface between the DLC film and the Si substrate by application of the DC bias.

Band-Edge Luminescence at Room Temperature of Boron Nitride Synthesized by Thermal Chemical Vapor Phase Deposition

We successfully synthesized hexagonal boron nitride (hBN), which exhibits intense intrinsic band-edge luminescence in the UV region, on a polycrystalline nickel substrate by thermal chemical vapor phase deposition. In cathodoluminescence (CL) spectra measured at room temperature, the deposited boron nitride (BN) exhibited an intense free-exciton luminescence peak at 215 nm with another luminescence peak at 226 nm. The line width of the Raman peak of the deposited BN is comparable to that of single-crystal hBN synthesized by a high-pressure/high-temperature (HPHT) method. These results indicated that the deposited BN has as high crystallinity as single-crystal hBN synthesized by a HPHT method.

Tribological properties of a-C:H films coated by the PBII method

Abstract Amorphous hydrogenated carbon (a-C:H) films were synthesized by the plasma-based ion implantation (PBII) technique using an electron cyclotron resonance plasma source with a mirror field with the simultaneous application of a DC and a pulse bias to the substrate. The influence of the duty ratio of the pulse biasing on the property and the uniformity of the a-C:H films for three-dimensional surfaces were investigated. An a-C:H film with a low friction coefficient (0.02) and low wear rate (6×10 −8 mm 3 /Nm) under a high conducted load (20 N) could be formed by the simultaneous application of a pulse (−2 kV) of low duty ratio (1%) and a DC bias (−200 V). The thickness, structure, and friction coefficient of the a-C:H film for the three-dimensional surfaces were very uniform. Furthermore, the deposition of a-C:H films on a drilling tool of high-speed steel was carried out, and a uniform film was obtained, because a uniform plasma was formed around the drilling tool. Finally, the uniformity of the film thickness for three-dimensional surfaces was improved within ±10% in distribution by both the DC biasing and the pulse biasing with a short duration.

Synthesis of amorphous carbon films by plasma-based ion implantation with simultaneous application of DC and pulse bias

Abstract Carbon films were synthesized on a Si wafer by simultaneous application of pulse bias and DC bias by a plasma-based ion implantation system using an electron cyclotron resonance (ECR) plasma source with a mirror field. The relationship between the pulse biasing voltage and the properties of carbon films was investigated. The hardness and tribological properties of the carbon film improved as the pulse bias voltage was decreased from −10 kV to −2 kV. Diamond-like carbon (DLC) films with a low friction coefficient were formed by simultaneous application of a low pulse bias voltage, such as −2 kV, and a DC bias. During the friction test of the DLC film, excellent tribological properties were observed under a high conducted load, such as 20 N, which shows that not only the friction coefficient but also the durability during the friction test was improved. The improvement of the tribological property was attributed to the formation of a mixed layer at the interface between the DLC film and the Si substrate.

Influence of DC biasing on the formation of hydrogenated amorphous carbon films using a plasma-based ion implantation technique

Carbon films were synthesized on a Si wafer by pulse biasing and DC biasing in a plasma-based ion implantation system using an electron cyclotron resonance (ECR) plasma source with a mirror field, and the influence of DC biasing with additional pulse biasing on the properties of carbon films was investigated. Diamond-like carbon (DLC) films with a low friction coefficient could be formed by the application of both a pulse bias and a DC bias. The tribological property was considerably improved by increasing the DC bias voltage up to -200 V for DLC formation, which shows the low friction coefficient under a high load conducted during the friction test. The improvement of the tribological property was attributed to the increase in the thickness of the mixed layer formed at the interface between the DLC film and the Si substrate upon DC biasing without the transition of structure from that of DLC to one similar to glassy carbon.

The influence of DC biasing on the uniformity of a-C:H films for three-dimensional substrates by using a plasma-based ion implantation technique

Abstract Amorphous hydrogenated carbon (a-C:H) films were synthesized by the use of a PBII technique using an electron cyclotron resonance plasma source with a mirror field, and the influence of the biasing conditions on the properties and the uniformity of the three-dimensional surfaces of a-C:H films was investigated. For convex faces, the film thickness was almost constant, independent of the deposition conditions, because a uniform plasma surrounded the substrates. For concave faces, the thickness of the films that formed without biasing and with only the application of a pulse bias decreased when the microwave-incident angle was decreased. On the other hand, when a DC bias was applied to the substrate in addition to a pulse bias, the uniformity of the thickness was much improved with a distribution within ±10%. The improvement in the uniformity was assumed to be the result of the continuous supply of ions in the plasma to the surfaces by the DC biasing.

X-Ray Magnetic Scattering in Fe-3 wt%Si

The intensity of interference scattering which originates in the product of charge and magnetic X-ray scattering amplitudes is successfully separated from the charge (Thomson) scattering intensity in the (220) reflection of Fe-3 wt%Si. Using intense elliptically polarized X-rays of about 1011 photons/s, sufficient counts can be accumulated within a short measuring time of about 6 minutes. The magnetic form factor determined from the interference scattering intensity agrees in sign and amplitude with the theoretical value.

Synthesis of a-C thin films by plasma-based ion implantation using an electron cyclotron resonance plasma source with a mirror field

Abstract Diamond-like carbon (DLC) films were synthesized by the plasma-based ion implantation technique, and the influence of the raw material used and the duty ratio of the pulse bias to the target on the properties of the DLC films was investigated. DLC films prepared by applying a pulse bias with a low duty ratio using either CH 4 or C 2 H 2 gas showed a good tribological property. A Cue5f8H absorption band measured by Fourier transform infrared absorption spectroscopy was not observed within the detection limit in the DLC films formed using CH 4 gas with the application of a pulse bias of a low duty ratio, but it was in the DLC films formed using C 2 H 2 gas. On the other hand, according to elastic recoil detection analysis, the hydrogen content remaining in the film formed using CH 4 gas was more than that remaining in the film formed using C 2 H 2 gas. We assume that hydrogen atoms remaining in the film formed using CH 4 gas were not bonded with carbon atoms and existed in the interstitial site in the film. We consider that these differences of the properties of the DLC films formed using CH 4 or C 2 H 2 gas resulted from the difference of the thickness of the modified carbon layer by the application of a pulse bias.