Eungsun Byon

Characterization of ternary boron carbon nitride films synthesized by RF magnetron sputtering

Boron carbon nitride (BCxNy) films were deposited on silicon wafers by RF magnetron sputtering of boron and graphite targets. BCN films with different compositions were obtained by varying the sputtering power of the graphite target (60, 180, 240 W). Chemical bonding states, composition and structure of the films were investigated by FTIR, XPS and AES analysis. The BCN films synthesized in this work were found to be BCN hybridized amorphous material, whose microstructure was examined with TEM observation. Mechanical properties of BCN films were compared to find the effect of the carbon sputtering power and resultant compositional changes on this ternary system. A BCN film with hardness of 15 GPa was synthesized at the high power of carbon source. With a higher sputtering power of carbon, hardness, elastic modulus and friction coefficients of a BCN film were increased due to the increase of strong BC, CC and CN bonds in the amorphous BCN film.

Coalescence of nanometer silver islands on oxides grown by filtered cathodic arc deposition

Ultrathin silver films have been deposited on glass and oxide-coated glass using filtered cathodic arc deposition and, for comparison, magnetron sputtering. The energetic differences between these deposition methods lead to initially different film properties. Silver films made by cathodic arc deposition show an earlier onset of island coalescence, indicating a lower aspect ratio than islands produced by evaporation and sputtering. However, the as-deposited films are thermodynamically unstable, exhibiting changes on a timescale of minutes. While films of islands tend to increase their sheet resistance with time, the sheet resistance of contiguous films shows a decrease. Both effects can be explained by silver mobility driven to minimize film and interfacial energy.

Bone response of Mg ion‐implanted clinical implants with the plasma source ion implantation method

OBJECTIVES This study examined the bone response of magnesium (Mg) ion-implanted implants produced using a plasma source ion implantation method. MATERIALS AND METHODS The surface characteristics were evaluated by scanning electron microscopy, Auger electron spectroscopy, X-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy. The screw-type titanium implants were treated with resorbable blasting media (RBM) and divided into one control group (RBM implants) and three test groups (Mg ion-implanted implants with different retained Mg doses). Twenty-four implants from each group were placed into the tibiae of 24 New Zealand white rabbits. After allowing 6 weeks for healing, the removal torque (RTQ) was measured and the implants were subjected to histomorphometric analysis. RESULTS The surface roughness and surface morphology of the test groups were similar. The Mg ion-implanted implants with a 2.3 x 10(15) ions/cm(2) retained dose showed a significantly higher RTQ than the other implants. Histomorphometric analysis indicated that the bone contact of this group was superior to the other groups. CONCLUSION The bone response of Mg ion-implanted implant showed results superior or similar to an RBM-treated implant. The optimal Mg ion concentration that induced the strongest osseointegration was approximately 9%.

Bias and self-bias of magnetic macroparticle filters for cathodic arc plasmas

Curved magnetic filters are often used for the removal of macroparticles from cathodic arc plasmas. This study addresses the need to further reduce losses and improving plasma throughput. The central figure of merit is the system coefficient Kappa defined as filtered ion current normalized by the plasma-producing arc current. The coefficient Kappa is investigated as a function of DC and pulsed magnetic field operation, magnetic field strength, external electric bias, and arc amplitude. It increases with positive filter bias but saturates at about 15 V for relatively low magnetic field ({approx}10 mT), whereas stronger magnetic fields lead to higher Kappa with saturation at about 25 V. Further increase of positive bias reduces Kappa. These findings are true for both pulsed and DC filters. Bias of pulsed filters has been realized using the voltage drop across a self-bias resistor, eliminating the need for a separate bias circuit. Almost 100 A of filtered copper ions have been obtained in pulse d mode, corresponding to Kappa approximately equal to 0.04. The results are interpreted by a simplified potential trough model.

Mechanical properties of BCN films deposited by dual cesium ion beam sputtering system

Abstract A study has been made on the formation of boron–carbon–nitride (BCN) thin films. The BCN thin films were synthesized using dual cesium ion beam sputtering system, which consisted of conventional magnetron sputter for carbon and boron sources and cesium flow system for negative ion generation. Nitrogen gas was introduced into argon plasma as a nitrogen source. Optimum process parameters were examined by the method of Taguchi L9 experiment. Hardness of BCN films was mainly affected by carbon sputtering power, working pressure and boron sputtering power in sequence. At the optimum process condition, the hardness and stoichiometry of BCN film were 30.6 GPa and BC 0.9 N 0.7 . From Fourier transform infrared spectroscopy results, it was found that the characteristics of the films had mixed with sp 2 BN, BC and CN bonding. The tribological behaviors of BCN films have been investigated by ball-on-disk tribometer. It is found that the friction coefficient is directly related to the film hardness and process parameters.

The effects of Mg‐ion implantation and sandblasting on Porphyromonas gingivalis attachment

OBJECTIVES The purpose of this study was to evaluate the effect of titanium surface treatment on Porphyromonas gingivalis bacterial attachment. MATERIALS AND METHODS Titanium disks of 15 mm in diameter and 1 mm in thickness (n=40) were subjected to mechanical grinding, or sandblasting. Magnesium (Mg) ions were implanted onto the titanium surface using a plasma source ion implantation method. The structure, chemistry, and surface morphologies of the titanium surfaces were analyzed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy and Auger electron spectroscopy. Surface roughness was measured using a laser profilometer. Half of the titanium disks in each group were dipped in saliva for 24 h. All of the titanium specimens were rinsed with distilled water. A P. gingivalis strain was cultured in anaerobic conditions at 37°C for 72 h, and all titanium specimens were dipped in the bacterial suspension at 37°C for 24 h. Specimens were examined at × 3000 magnification using a SEM. The number of bacteria in each of 10 separate fields was determined by directly counting the number of bacterial colonies that adhered to each specimen. The mean values were calculated afterward. The resulting data were analyzed to assess the significance of observed differences based on the method of the surface treatment, ion implantation, and saliva dipping. RESULTS The amount of P. gingivalis attached to the sandblasted specimens was greater than that on the ground specimens (P<0.001). Moreover, surfaces with Mg-ion implantation had more attachments than nonimplanted surfaces (P<0.001). Saliva dipping acted synergistically with surface roughness and chemical composition of the specimens. CONCLUSIONS Chemically modified surface increase the attachment of a major periodontopathic bacterium, P. gingivalis.

Corrosion behavior of boron-carbon-nitride films grown by magnetron sputtering

The corrosion behavior of BCN thin films in aqueous solution was investigated. BCN films with different composition were deposited on a platinum plate by magnetron sputtering in the thickness range of 150–280 nm. In order to understand effect of pH of solutions, BC2.4N samples were immersed in 1 M HCl, 1 M NaCl and 1 M NaOH solution at 298 K, respectively. BCN samples with different carbon content were immersed in 1 M NaOH solutions to investigate the effect of chemical composition on corrosion resistance. The corrosion rate of the samples were measured by ellipsometry. The corrosion rates of B1.0C2.4N1.0 films in the immersion test were NaOH>NaCl>HCl in sequence. With increasing carbon content in BCN films, the corrosion resistance of BCN films is enhanced. The lowest corrosion rate was obtained for B1.0C(3.2–4.4)N1.2 films.

Gene expression in Ca or Mg implanted titanium surfaces

It may be essential to know the behavior and gene expression of osteoblasts cultured on chemically modified surfaces to understand their surface properties in vivo. The purpose of this study was to compare the initial cDNA cellular response to calcium (Ca)- and magnesium (Mg)-ion implanted titanium surfaces. Mg ions and Ca ions were implanted onto ground titanium using the plasma source ion implantation technique. The structural and surface properties of the specimens were analyzed by scanning electron microscopy, auger electron spectroscopy, and Rutherford back-scattering spectroscopy. The MTT assay was used for examining the attachment of MC3T3-El cells, and cDNA microarray was used for the identification of differentially expressed genes. After ion implantation, the surface roughness and morphology did not change. The atomic concentrations of Mg and Ca were similar, while the Ca ions had higher oxygen affinity than Mg ions. The MTT assay showed an increase in the cell attachment on the Mg- and Ca-implanted surface. In the cDNA microarray analysis, the Ca-implanted surface showed more upregulated gene expression than the Mg-implanted surface. Also, the biocompatibility-related genes were expressed more on the Ca-implanted surface.

Effect of solenoid magnetic current on the beam extraction of filtered vacuum arc source (FVAS)

Abstract In this study, a new type of filtered vacuum arc source (FVAS) was designed, which was composed of a torus structure with bending angle of 60°. The radius of torus and plasma duct was 266 mm and 80 mm, respectively, and the total length was 600 mm. The magnet part was composed of one permanent magnet, one magnetic yoke and five solenoid magnets. The cathode evaporation region with a modified magnetic mirror configuration was adapted. The plasma duct was electrically isolated from the ground so that a bias voltage could be applied. The cathode was made of graphite and was 80 mm in diameter. A computer simulation and experiment using the Taguchi method (design of experiment) studied the effects of a solenoid magnet on plasma extraction. The source and extraction magnet affected the arc stabilization. The extraction beam current was maximized with a low value of the source magnet current and a high value for the filtering magnet current. The maximized values of the beam current density of 1.8 mA cm2 and average deposition rate of 5 A/s were obtained at the conditions of the arc discharge current, source, extraction and bending magnet were 30 A, 1 A, 3 A and 3 A, respectively.

Effects of Mg-ion and Ca-ion implantations on P. gingivalis and F. nucleatum adhesion

The purpose of this study was to evaluate the effects of ion implantation on Porphyromonas gingivalis (P. gingivalis) and Fusobacterium nucleatum (F. nucleatum) bacterial adhesion. Titanium (Ti) discs of 15 mm diameter and 1 mm in thickness (n = 42, 7 per group) were fabricated. Magnesium (Mg) and calcium (Ca) ions were implanted into the Ti surfaces using a plasma-source ion-implantation method. The roughness, chemistry, morphology, and contact angle of the titanium surfaces were analyzed using scanning electron microscopy, Rutherford back-scattering spectroscopy, Auger electron spectroscopy, and contact angle meter. P. gingivalis and F. nucleatum strains were cultured in anaerobic conditions at 37°C for 72 hours, and all titanium specimens were dipped in the bacterial suspension at 37°C for 24 hours. Specimens were examined at 1,000× magnification using a fluorescence microscope. The number and total area of bacteria in each of 10 separate fields were determined by computer imaging analysis method. The resulting data was analyzed to assess the significance of observed differences based on the method of the surface treatment, ion implantation. The number of P. gingivalis and F. nucleatum attached to the Mg-(927 and 227, respectively) and Caionimplanted (1325 and 231, respectively) surfaces were greater than those attached to the non-implanted surfaces (306 and 98, p <.001). Total area occupied by P. gingivalis adhesion was greater than those of F. nucleatum in the Mgand Caion-implanted surfaces (p <.001). The types of ion and bacteria did not affect the amount of bacterial adhesion. Ion implantation enhanced the adhesions of P. gingivalis and F. nucleatum. Non-specific bonding derived from the electrostatic force affected by positively charged ions might be the predominant factor in bacterial adhesion. The possibility of specific bonding could not be ruled out in the Ca-ion- implanted surface.