We carried out shallow depth indentations on ultra-thin hydrogenated amorphous carbon (a-C:H) films deposited by plasma enhanced chemical vapour deposition onto silicon and Al2O3-TiC ceramic substrates. These measurements are relevant to data storage and microelectronic applications, which require sub-50-nm, wear protective overcoats. Weused the continuous stiffness measurement technique to monitor the Young Modulus (E) and the hardness (H) as a function of depth for films with thickness varying from 10 to 50 nm. Raman spectroscopy and atomic force spectroscopy show that the films have similar roughness and microstructural bonding environment. For all films, the sub-30-nm region shows a continuous increase of E and H with depth, with no discernible tip calibration artifact. Above 30 nm depth, the effect of the film is predominant, essentially hardening noticeably the silicon and softening slightly the ceramic substrate, with E and H valuestypical of a-C:H materials. Above 50 nm, the E and H curves are dominated by the properties of the substrates. Initial nano-scratch experiments indicate that the films have better wear resistance than the Al2O3-TiC substrate. Therefore, the hardness and wear of the samples show no correlation at these shallow depths. (C) 2000 Elsevier Science B.V. All rights reserved.