Diamond-like carbon (DLC) films were deposited on the inner wall surface of 304 austenitic type stainless steel tubes with inner diameter of 0.9 and 0.5 and 15 mm length by a plasma source ion implantation (PSII). A 2.45 GHz microwave was fed into a tubular vacuum chamber and supplied to an antenna. An acetylene gas was fed into the alumina ceramic tube. Plasma was produced by a coaxial electron cyclotron resonance (ECR) discharge. A magnetic field of one kilogauss was generated by a solenoidal coil. The negative high voltage pulse (typically -10 kV, 1 kHz, 10 mus) was applied to the steel tube. The results showed that the DLC film deposition on the inner wall of sub-millimeter size steel tubes was achieved by the PSII Raman spectra of the DLC films showed a broad peak related to amorphous carbon structure. (C) 2003 Elsevier Science B.V. All rights reserved.