Femtosecond pulsed laser deposition of diamond-like carbon thin films for tribological applications

Pulsed laser ablation is a well-known technique used for thin film deposition of hard and wear resistant diamond-like carbon (DLC) films. Most of the previous studies were carried out by using pulse duration in the nanosecond range. Compared to conventional nanosecond laser ablation, femtosecond laser allows the production of high energy (up to a few keV) ions in the plasma, which may strongly affect the structure and properties of the deposited films. The present study was achieved by ablating graphite targets with femtosecond (10(-15) s range) laser pulses. DLC films were deposited under vacuum onto (1 0 0) p-type silicon substrates at room temperature. The laser pulse energy was 1.5 mJ at a repetition rate of I kHz. The fluence (or energy density) range was between I and 6 J/cm(2). The nature and mechanical properties of the films are characterized by X-ray absorption near-edge spectroscopy and nanoindentation techniques. The tribological behavior of the films are also investigated in a pin-on-plate configuration. Correlations between the structure of the films and some of their properties are highlighted, depending on the deposition conditions. Discussion is focused on the comparison between present results obtained using the femtosecond mode, with previously published results related to DLC films deposited using the nanosecond mode. (C) 2002 Elsevier Science B.V. All rights reserved.