The indentation depth effect has been systematically examined on the mechanical properties of electrodeposited nickel films under 0% and 10% tensile strains. It is found that the indentation depth is proportional to the square root of the loads applied and the depth profiles of hardness and elastic modulus follow the similar trend of change with maximal values at the surface skins. The hardness and modulus then attenuate to a value of about half of the maximum, which follows the model proposed by Graca et al., Surf. Coat. Technol. ͑in press͒ with the mechanism of geometrically necessary dislocations and surface free energy. We suggest that the effect of surface oxidation and surface bond contraction ͓C. Q. Sun, Prog. Solid State Chem. 35, 1 ͑2007͔͒ contributes intrinsically to the anomalous skin strengthening because of the local strain and energy trapping caused by surface bonds breaking.

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Ferroelectric LiNbO3 thin film of high near-c-axis orientation was grown on Si by pulsed laser deposition using a thin ZnO buffer layer of high c-axis orientation. Both the LiNbO3 film and the ZnO layer consist of columnar grains with random in-plane twist relative to each other. The c axes of LiNbO3 grains tilt small angles with respect to the film growth direction and the deviation angles follow nearly Gaussian probability distribution within 5°. The out-of-plane tilt nucleation of LiNbO3 lattices on the waved surfaces of the ZnO layer leads to the near-c-axis oriented growth of the LiNbO3 film.

The creep behaviour of polycrystal Ni thin films under the same maximum load (Pmax = 8000 microN) and different unloading periods (ranging from 1 to 250 s) has been investigated at room temperature using nanoindentation tests. A 'nose' has been observed in the unloading segment of the load-penetration depth curve when the holding time at peak load is short and/or the unloading rate is small, and when the peak load is sufficient high. When a 'nose' presents, the apparent unloading stiffness Su, defined as dP/dh, is negative, and the reduced modulus can no longer be calculated from the Oliver-Pharr method. Taking such uncertainties into account, a critical appraisal is proposed for ranking creep propensities exhibited during nanoindentation under specified conditions.

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