The plasma formed during the laser ablation of a carbon target has been studied by optical emission spectroscopy and Langmuir electrostatic probes in order to investigate the kinetic energy of the ions, and the plasma density as a function of the target-to-substrate distance and the laser intensity. The experiments were carried out using a Nd:YAG laser with emission at the fundamental line, with a maximum energy output of 150 mJ. In our experimental conditions the plasma emission is principally due to C+ (283.66, 290.6, 299.2 and 426.65 nm) and C2+ (406.89 and 418.66 nm). The ion energies detected varied in a wide range, from similar to 100,up to 500 eV The highest plasma densities (9 x 10(13) cm(-3)) that could be detected with the probe were measured at 6 cm from the target, and the lowest (5 x 10(11) cm(-3)) were measured at 15 cm. The characterized plasma regimes were used for the deposition of a-C films under different ion energies and plasma densities, so that different percentages of sp(3) bonding might be formed in the deposits. The films were analysed using Raman spectroscopy, EELS and EDS. (C) 2003 Elsevier Science B.V. All rights reserved.