Jong-Kuk Kim

Effect of ion mass and charge State on transport of vacuum arc plasmas through a biased magnetic filter

The effect of ion mass and charge state on plasma transport through a 90/spl deg/-curved magnetic filter is experimentally investigated using a pulsed cathodic arc source. Graphite, copper, and tungsten were selected as test materials. The filter was a bent copper coil biased via the voltage drop across a low-ohm, self-bias resistor. Ion transport is accomplished via a guiding electric field, whose potential forms a trough shaped by the magnetic guiding field of the filter coil. Evaluation was done by measuring the filtered ion current and determination of the particle system coefficient, which can be defined as the ratio of filtered ion current, divided by the mean ion charge state, to the arc current. It was found that the ion current and particle system coefficient decreased as the mass-to-charge ratio of ions increased. This result can be qualitatively interpreted by a very simple model of ion transport that is based on compensation of the centrifugal force by the electric force associated with the guiding potential trough.

Synthesis and Characterization of Ti-Si-C-N Nanocomposite Coatings Prepared by a Filtered Vacuum Arc with Organosilane Precursors

Many deposition tools such as magnetron sputtering, plasma enhanced chemical vapor dep‐ osition (PECVD), arc ion plating (AIP), and filtered vacuum arc (FVA) have been introduced for synthesizing nanocomposite films. Table 1 summarizes previous works of nanocompo‐ site coatings. Nanocomposites based on TiN have been investigated dominantly with the in‐ corporation of silicon or carbon contents. The incorporation methods such as an alloy arc cathode, addition of reactive gas, and additional magnetron sputtering have been used to deposit ternary or quaternary composition nanocomposite films. The magnetron sputtering and PECVD have been firstly used to grow nanocomposite films due to the simplicity of controlling a composition ratio becuase precise control of additional components is impor‐ tant to make a nanocomposite structure. For example, Ti-Si-N nanocomposite films have showed the maximum hardness at Si content of 9±1 at.% [1]. After that, a vacuum arc dis‐ charge has been applied to the nanocomposite coatings becuase the vacuum arc process has many advantages against other CVD or PVD processes. A vacuum arc plasma exhibits high ionization ratio more than 90%. Also the ion energy in a vacuum arc is in the range of 10-100 eV. Hence, the effect of ion energy on the film structure appears significantly [2]. Neverthe‐ less, the vacuum arc method cannot avoid the problem of macro particles. Macro particles generated from arc spots are the main drawback of the vacuum arc process. The macro par‐ ticles form micro cracks or pin holes, resulting in a bad corrosion resistance when coatings are exposed in some corrosive environments.

Development of Surface Treatment for Hydrophobic Property on Aluminum Surface

A hydrophobic surface has been fabricated on aluminum by two-step surface treatment processes consisting of structure modification and surface coating. Nature inspired micro nano scale structures were artificially created on the aluminum surface by a blasting and Ar ion beam etching. And a hydrophobic thin film was coated by a trimethylsilane () plasma deposition to minimize the surface energy of the micro nano structure surface. The contact angle of micro nano structured aluminum surface with the trimethylsilane coating was (surface energy: 9.05 ), but the contact angle of only trimethylsilane coated sample without the micro nano surface structure was (surface energy: 99.15 ). In the hydrophobic treatment of aluminum surface, a trimethylsilane coated sample having the micro nano structure was more effective than only trimethylsilane coated sample without the micro nano structure.

Nanocomposite Films Deposition by means of Various Filtered Vacuum Arc Systems

A hard coating is of considerable significance in industrial applications such as high speed cutting tools. The hard coating technologies have been investigated to improve a life time as well as performance of the tools. Up to now, TiN coatings were widely used. However, the substitution of TiN has been required because of its low oxidation temperature of 500 oC. From 1970s, it was revealed that nanocomposite films have their infinite probability enough to replace the previous materials such as TiN. Nanocomposite materials such as nanocrystalline TiN/Si3N4, TiN/TiC/Si3N4, and TiN/AlN/Si3N4 exhibited superior oxidation temperature (~1000 oC) as well as ultra hardness (45-55 GPa) [1-6]. Many deposition tools like a magnetron sputtering, plasma enhanced chemical vapor deposition (PECVD), arc ion plating (AIP), and filtered vacuum arc (FVA) were introduced for synthesizing nanocomposite films. Table 1 summarized previous works of nanocomposite coatings. Nanocomposite films based on TiN were dominantly investigated with the incorporation of silicon or carbon. The incorporation methods such as an alloy arc cathode, addition of reactive gas, and additional magnetron sputtering were used to deposit ternary or quaternary composed nanocomposite films. The magnetron sputtering and PECVD have been firstly used to the growth of nanocomposite films due to the simplicity of controlling a composition ratio. Precise composition control of additional components is important. For example, Ti-Si-N nanocomposite films represent the maximum hardness at Si content of 9±1 at.%. After that, a vacuum arc discharge has been applied to the nanocomposite coatings because it can generate dense plasma with energetic ions near a cathode spot (<60 eV), which help a delicate crystallization and rapid growth. Nevertheless, the vacuum arc method cannot avoid the problem of macro particles emitted at an arc spot. The macro particles make some defects in the coatings and result in drastically decreasing corrosion resistance when the coatings are exposed in the corrosive environment. Therefore magnetic filters have been introduced to transport plasma except the macro particles. The filters only transport charged particles using electromagnetic fields and the neutral macro particles collide with a filter wall by an inertia drift. As a result, various FVA methods have been widely applied to the nanocomposite deposition.

Surface Modification of WC-Co and SCM415 by the Ion Bombardment Process of Filtered Vacuum Arc Plasma

The surfaces of WC-Co and SCM415 were etched to form a micro size protrusion for oil based ultra low friction applications using an ion bombardment process in a filtered vacuum arc plasma. WC-Co species showed that a self-patterned surface was available by the ion bombarding process due to the difference of sputtering yield of WC and Co. And the increasing rate of roughness was 0.6 nm/min at -600 V substrate bias voltage. The increasing rate of roughness of SCM415 species was 1.5 nm/min at -800 V, but the selfpatterning effect as shown in WC-Co was not appeared. When the SCM415 species pretreated by electrical discharge machining is etched, the increasing rate of roughness increased from 1.5 nm/min to 40 nm/min at -800 V substrate bias voltage and the uniform surface treatment was available.