Yong M. Kim

Atmospheric RF plasma effects on the film adhesion property

Abstract Commercial polymers in thin film form were used for modification by atmospheric RF plasma. The influence of the plasma treatments using Ar and Ar+O 2 on surface energy, morphology and chemical structure of the films was investigated. It was revealed that both modifications caused surface activation of the polymer film, but they obeyed different mechanisms enhancing polymer wettability. First, surface graphitization due to argon sputtering caused hydrogen to free the surface and then reacts with oxygen in the air. Second, surface oxidation is connected with the functional group formation. The reactions of Ti with the polymer led to the simultaneous formation of TiCl 2 , TiC, Ti-oxide and they contributed to film adhesion. In comparison with Ar, the mixed Ar+O 2 RF plasma treatment was a more timesaving process and had more influences on surface activation and film adhesion.

Investigation on the pulsed DC plasma nitriding with optical emission spectroscopy

Abstract We have investigated nitriding behavior by a pulsed DC plasma nitriding process. For effective control, it is necessary to monitor the density of the active nitrogen species in the plasma, which is responsible for the enhanced plasma–ferro-metal reaction. An optical emission spectroscopy (OES) method was employed for diagnostic analysis of the plasma during the processes. In this study, AISI H13 steels were nitrided at 550 °C for 4 h with various discharge times and nitrogen concentrations. Active species such as N 2 + , N 2 * were evaluated in terms of the first negative system [N 2 + (B 2 Σ u + , ν ′)→N 2 + (X 2 Σ g + , ν″ + hν ], the second positive system [N 2 (C 3 Π u , ν ′)→N 2 (B 3 Π g , ν″ )+ hν ] of nitrogen and Balmer series of hydrogen by OES. In addition, the structures of the samples were analyzed by XRD. It was found that the compound layer consists of the dominant γ′-Fe 4 N phase.

Titanium density analysed by optical absorption and emission spectroscopy in a dc magnetron discharge

This paper presents an optical diagnostic examination of dc planar magnetron discharge used for titanium deposition at 30 mTorr in argon bulk gas. The results were obtained by optical absorption (OAS) and emission (OES) spectroscopy for two distances from the target without substrate. The absolute density of titanium in the ground and metastable states at 4 cm from the target ranged, respectively, between 8 × 1010 cm−3 and 1012 cm−3 and between 6 × 1010 cm−3 and 3 × 1011 cm−3, in the range 0.2–1.0 A. OES results were used to prepare an assumed interpretation in terms of differences in loss mechanisms, mainly by either diffusion towards the walls for all particles at 8 cm from the target or collision losses for non-radiative species at 4 cm from the target, except for the titanium ground state. This was confirmed by our results of the argon metastable density measurement at 4 cm which was constant at around 7 × 1010 cm−3 with discharge current.

Spectroscopic study for pulsed DC plasma nitriding of narrow deep holes

Abstract The nitriding behavior of the inner surfaces of narrow blind holes with various diameters was investigated by the pulsed DC plasma nitriding process. Optical emission spectroscopy with an optical probe was employed for diagnostic analysis of the plasma during the processes. Active species were analyzed using an optical probe in front of narrow blind holes with diameters of 3–5 mm and a penetration depth of 30 mm. AISI H13 steel was nitrided at 550 °C for 3 h at various pulsed DC duty cycles, nitrogen and hydrogen partial pressures. The hollow-cathode discharge was effectively stabilized by controlling the pulse duty cycle and working pressure. The plasma stability in a narrow hole appeared to be enhanced by increasing working pressure and decreasing pulse duty cycle.

Deposition of TiOx thin film using the grid-assisting magnetron sputtering

This paper presents a modification to conventional magnetron sputtering systems. The introduction of a grid in front of the target increases metal ion ratio in the plasma. By using optical emission spectroscopy (OES) and observing both Ti neutral and Ti ion, the relative ionization could be qualitatively extended to grid-attached magnetron sputtering as compared with conventional magnetron systems. Experiments clearly demonstrate microstructural cross-sectional TEM analysis of the titanium oxide film changes from a columnar-like (anisostropic) structure to a homogenous structure (isotropic), and resulting in a high refractive index. It is believed that more energetic ion bombardment induced the structural changes in films in the case of grid-assisted magnetron sputtering.

Deposition of TiN thin films using grid-assisting magnetron sputtering

Summary form only given, as follows. It is well known that thin film growth and surface morphology can be substantially modified by ion-bombardment during the deposition. This is particularly important in case of thin-film deposition at low temperatures where the film growth occurs under highly nonequilibrium conditions. An attractive way to promote crystalline growth and surface morphology is deposition of additional energy into the surface of the growing film by bombardment with hyperthermal particles. We deposited crystalline Ti and TiN thin films on Si substrate by magnetron sputtering method with grid. Its thin films were highly smoothed and dense as increasing grid bias. In order explore the benefits of a bombardment of the growing film with high energetic particles, Ti and TiN films were deposited on Si substrates by an imbalanced magnetron sputter source with attached grid assembly for energetic ion extraction. Also, we have studied the variation of the plasma states for the feedback control of nucleation and growth behavior by Langmuir probe and Optical Emission Spectroscopy (OES). The epitaxial orientation, microstructual, optical characteristics and surface properties of the films were analyzed by XRD, SEM, ellipsometry and AFM.