Grid-enhanced Plasma Source Ion Implantation Research Articles

Double Temperature and Density Phenomenon in Grid Enhanced Plasma Source Ion Implantation for Inner Surface Modification of Tubes

Inner surface coating for tubular samples was realized by the grid enhanced plasma source ion implantation (GEPSII) method. In the GEPSII system, two electrodes, a central rod electrode and a coaxial grid electrode were coaxially assembled inside the tube. Plasma was generated between the electrodes by a radio-frequency (RF) oscillating power source. Plasma then diffused through the grid and realized inner surface ion implantation by a negative high voltage applied to the tube. The plasma was then divided, by the grid, into two regions, namely the source plasma region and the diffused plasma region. The plasma's self-bias between two RF power source electrodes was measured. At the same time, the electron temperature and plasma density in the GEPSII system were measured by a scattering spectrometer. Results showed that the plasma properties of the two regions were entirely different; the plasma self-bias, which might greatly affect the sputtering rate of the central titanium electrode, depended on the electrode structure, gas pressure and RF power.

Axial property of the inner surface of a metal tube processed by GEPSII

As a novel inner surface processing method, grid enhanced plasma source ion implantation (GEPSII) method can realize uniform inner surface ion implantation of a metal tube and metal binary compound can be produced. In the experiment, three 0.45% carbon steel (45-steel) work pieces were axially put on the inner surface of the tube, and golden titanium nitride (TiN) films were produced on the work pieces by GPSII. Structure analysis shows that the TiN films have the preferred crystal faces (111) and (200), and the depth of the films is about 20 nm with partial embedding in the substrate. Analysis on the electrochemistry corrosion, hardness and friction of the work pieces indicates that the surface property of the 45-steel has been greatly improved by the protective TiN film, and very good axial uniformity has been obtained.

Properties of TiN coating on 45 # steel for inner surface modification by grid-enhanced plasma source ion implantation method

Using a new inner surface modification method named GEPSII (grid-enhanced plasma source ion implantation), which is designed for inner surface modification of tubular work pieces, we successfully produced polycrystalline TiN coating on 0.45{%} C steel (45# steel) samples. Compared with the uncoated 45# steel sample, the electrochemical corrosion test on the coated 45# steel samples presents evident improvement in their corrosion resistance. Two implanted voltages, direct current (–2kV) and pulsed negative voltage (–10kV), are applied on the substrates. It is shown that the direct current implantation is more effective than the pulsed implantation in the surface corrosion resistance. AES depth profile shows that coating thickness is about tens of nanometres. The preferred orientations expressed by peaks at (111) and (200) can be seen clearly in XRD patterns.

Grid-shadow effect in grid-enhanced plasma source ion implantation

A grid-shadow effect is observed in grid-enhanced plasma source ion implantation (GEPSII), in which ions produced within the plasma region are extracted through a grid electrode and are then accelerated to the inner surface of a cylindrical bore for implantation. By simulating the ion transportation behaviors from the grid electrode to the inner surface using a Monte Carlo model, we find that the grid-shadow effect results from grid blocking of the ion emission on the grid electrode and that it varies with the experimental parameters such as the gap distance between the grid electrode and the inner surface, the gas pressure, and the applied negative potential.

Influence of ion species ratio on grid-enhanced plasma source ion implantation

Grid-enhanced plasma source ion implantation (GEPSII) is a newly proposed technique to modify the inner-surface properties of a cylindrical bore. In this paper, a two-ion fluid model describing nitrogen molecular ions N2+ and atomic ions N+ is used to investigate the ion sheath dynamics between the grid electrode and the inner surface of a cylindrical bore during the GEPSII process, which is an extension of our previous calculations in which only N2+ was considered. Calculations are concentrated on the results of ion dose and impact energy on the target for different ion species ratios in the core plasma. The calculated results show that more atomic ions N+ in the core plasma can raise the ion impact energy and reduce the ion dose on the target.

Influence of grid and target radius and ion–neutral collisions on grid-enhanced plasma source ion-implantation process

Grid-enhanced plasma source ion implantation (GEPSII) is a newly proposed technique for inner surface modification of materials with cylindrical geometry. In this paper, a collisional fluid model is used to investigate the ion sheath dynamics between the grid electrode and the inner surface of a cylindrical bore during the GEPSII process. Assuming the initial ion density along the radial direction is not uniform but determined by diffusion mechanisms, the effects of grid electrode radius, target radius and ion–neutral collisions on the ion dose and impact energy are investigated by solving fluid equations for ions coupled with Boltzmann assumption for electrons and Poisson's equation. The results show that small gap distance between grid electrode and target is favourable to increase the ion dose and impact energy on the target. In addition, ion–neutral collisions can reduce both the ion dose and impact energy.

TiN coating for inner surface modification by grid enhanced plasma source ion im plantation

Using the new inner surface modification technique named GEPSⅡ(grid-enhanced pl asma source ion implantation), which is designed for inner surface modification of tubular work piece, has successfully produced TiN coating on 0.45% C steel (4 5# steel). By comparing with the uncoated 45# steel sample, the electrochemical corrosion test on the coated 45# steel samples presents about 5—10 times improv ement in their corrosion resistance. Structural analysis shows that the TiN coat ings have preferred crystal orientation(111) and (2000). And the depth of coatin gs is about 20 nm, with part of which embedding in the substrate.

Pulsed Ion Sheath Dynamics in a Cylindrical Bore for InnerSurface Grid-Enhanced Plasma Source Ion Implantation

Based on our recently proposed grid-enhanced plasma sourceion implantation (GEPSII) technique for inner surface modification ofmaterials with cylindrical geometry, we present the correspondingtheoretical studies of the temporal evolution of the plasma ion sheathbetween the grid electrode and the target in a cylindrical bore. Typicalresults such as the ion sheath evolution, time-dependent ion densityand time-integrated ion energy distribution at the target are calculatedby solving Poisson's equation coupled with fluid equations forcollisionless ions and Boltzmann assumption for electrons using finitedifference methods. The calculated results can further verify thefeasibility and superiority of this new technique.

Inner surface coating of TiN by the grid-enhanced plasma source ion implantation technique

An inner surface coating of a tubular sample was realized by a new method of grid-enhanced plasma source ion implantation (GEPSII), which is an extension of previous plasma source ion implantation inner surface modification. In GEPSII, a rf plasma core is produced between a center cathode and a grid electrode, which are coaxially arranged inside the tubular sample. Negative high voltage pulses are applied between the grid electrode and the inner surface of the tubular sample, thus an accelerating field for positive ions can be established between the grid electrode and the inner surface of the sample. In addition, particles of solid matter can be introduced into the rf plasma by sputtering the cathode, thus, it is possible to realize metal ion implantation and film deposition. In this article, the concept of GEPSII and some preliminary measurement results of this method are presented, and TiN films are produced on the inner surface of a tubular sample, which is a cylinder of an automobile. The plasma density profiles and plasma electron temperature inside the sample are measured by a Langmuir probe. It is shown that the axial plasma density profile is rather uniform in GEPSII. TiN films were also deposited on single-crystal silicon substrates, which are arranged on the inner surface of the cylinder.