Thin films
Mechanical properties measurement for materials and thin films (hardness, adhesion, thickness) by a variable load scratch test
Thin films are used extensively as protective and wear-resistant coatings for a wide range of objects. Correct mechanical properties measurements of these films without the substrate influence is an important task in the modern quality control systems. Scanning nanohardness tester NanoScan-3D allows hardness measuring of the films by different methods for a wide range of thicknesses.
The most common method of measuring the physical and mechanical properties of thin films today is an instrumented indentation method. However, there are several factors that lead to methodological errors for this measurement method. The most critical of these are the surface roughness, residual stresses and the so-called «substrate effect», which consists in the fact that for a film-substrate system the response of the material depends both on the film properties and the substrate properties.
The scratch test method (scratching and analysis of scratches profile) has several advantages over indentation methods for measuring the films hardness in the nanoscale. Direct observation of the residual scratch trace by SPM allows minimizing the influence of the dominant elastic deformation which is typical for the indentation methods.
Scratching at variable load (Fig. 1) makes it possible to define several film parameters in a single measurement procedure: the elastic interaction area, the limiting load at which the plastic deformation starts (there is a visible trace on the surface), separation and delamination of the film.
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| Fig.1. A diamond-like film on a silicon substrate | |