Diamond-like carbon films with extremely low stress

We in this paper report different ways to realise thick diamond-like carbon (DLC) films with stress values lower than 0.5 GPa. Thick DLC films grown b y conventional r.f. self bias technique often delaminate from the substrate s due to the presence of high compressive stresses of the order of 4-7 GPa. We have made an in-depth study of the delamination problem of DLC films at NPL and found that only for substrates kept away from the plasma (plume) i t is possible to grow thick DLC films. This goes to show the heating of the substrates, when in contact with the plasma, appears to be one of the most important factors giving rise to the high stress values. Techniques that h ave produced consistently low stress values (0.2-0.5 GPa) in this laborator y are pulse plasma PECVD and the one using de saddle field fast atom beam s ource. Electronic properties of the materials so produced have been estimat ed by evaluating Urbach energy using photothermal deflection spectroscopy ( PDS) measurements. A correlation between the unbound hydrogen in these film s, as measured by a nuclear technique (ERDA), and the stress levels has bee n found. Deposition rate, room temperature conductivity, optical bandgap an d refractive index have also been measured for these films. (C) 1999 Elsevi er Science S.A. All rights reserved.