Diamond-like carbon (DLC) films have been grown on Si substrates at ambient temperature by the pulsed-laser ablation technique, using pulses of different durations both in the nano- and picosecond ranges and at various energy fluences. The stability of these films was investigated as a function of thermal anneals performed in UHV conditions up to 1273 K. Their physico-chemical properties have been characterized by different techniques including X-ray photo-emission, Auger electron and electron-energy-loss spectroscopies, Raman scattering, spectroscopic ellipsometry and atomic-force microscopy. The thermal stability of the films has been demonstrated to be related to their initial structural (sp3/sp2 ratio) and chemical (contaminant) properties. DLC layers prepared under optimized conditions have been found to show a very good thermal stability up to 900 K.