Deposition of tetrahedral diamond-like carbon thin films by femtosecond laser ablation for applications of hip joints

Tetrahedral diamond-like carbon films (ta-C) were deposited by femtosecond pulsed laser deposition (PLD) on various substrates, including 316L stainless steel and ultra high molecular weight polyethylene, in perspective to extend the wear resistance of materials used in hip joints. Usually films are deposited by plasma enhanced chemical vapor deposition or by PLD, principally performed with laser pulse duration in the nanosecond range. In the present study, DLC films were deposited by femtosecond laser ablation in high vacuum conditions at room temperature. The 800 nm, 150 fs laser pulses are generated by a mode-locked Ti:Sapphire laser, including an amplification stage. The fluence ranges from 1 to 6 J/cm(2). Sputter cleaning of the substrates in an argon atmosphere prior carbon deposition was widely investigated; the adhesion of the films onto the stainless steel substrates was then considerably enhanced by removing the contamination and oxidized top-coats. The adhesion properties of films deposited in various conditions on 316L stainless steel substrates were studied by tensile tests. The films exhibit high wear resistance (in the 10(-8) mm(3) N-1 m(-1) range) with moderate hardness (in the 20-30 GPa range), which may be favorable for the accommodation motion between contacting surfaces in a hip joint. The capacity of these films to satisfy the biomedical demand is discussed. (C) 2003 Elsevier B.V. All rights reserved.