The contact response of thin SiC-coated silicon systems—characterisation by nanoindentation

The detailed contact response of a range of epitaxial, cubic (3C)- SiC coatings on both (100) and (111) Si have been studied using nanoindentation techniques. In order to assess the influence of the coating thickness on the system properties, indentations were made to peak loads between 5 and 500 mN, creating displacements which either exceed, are of the same order of, or are less than the coating thickness. Besides calculating hardness (H) and Youngʹs modulus (E) as a function of the contact scale, load–displacement (P–δ) curves, load–vs.–displacement-squared (P∝δ2) and load–vs.–stiffness squared (P–S2) analyses have also been used to evaluate the detailed influence of the coating on the contact response. Deformation structures associated with the indentations have been characterised by scanning electron microscopy. The mechanical property enhancements provided by the coating have been quantitatively estimated including the fractional support of the contact load by the coating which contributes to a decrease in contact penetration at a given load. Interestingly, the differing scale-sensitive effects of the coating on both E and H imply that there is a critical contact scale at which a maximised elastic response is experienced and this could be exploited in design.