The hardness and elastic modulus of C, CNx and AIN thin films after rapid thermal annealing have been investigated using nanoindentation and microhardness measurements techniques. The thin films have been deposited on silicon by plasma enhanced chemical vapor deposition using CCl4, ksilol and NH3 as precursors for CNchi layers. The film thickness was between 30 and 150 nm. Carbon and AIN thin films have been prepared using rapid thermal annealing. It has been found that the highest values for hardness (17.7 GPa) correspond to the samples prepared with CCl4 and NH3 as precursors, and subjected to rapid thermal annealing at 1400 K min(-1). (C) 2003 Elsevier B.V. All rights reserved.