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.