[2] Ni T L, Ding F, Zhu X D, Appl. Phys. Lett., 2008, 92: 1503.
[3] Jeong J Y, Babayan S E, Tu V J, Plasma Sources Sci. & Technol, 1998, 7: 282.
[4] Xu L, Liu P, Zhan R J. Thin Solid Films, 2006, 506: 400.
[5] Chen G L, Chen S H, Zhou M Y, Plasma Sources Sci. & Technol, 2006, 15: 603.
[6] James M W. Peter B. Biswa N G. Journal of Physics D: Applied Physics, 2004, 37: 1658.