Between nanoindentation and scanning force microscopy: measuring mechanical properties in the nanometer regime

Interest in the properties of materials in small dimensions has led to the parallel development of nanoindentation and scanning force microscopy (SFM). Nanoindentation has extended indentation testing into the submicrometer regime via the development of suitable equipment and means of interpreting indentation load-displacement data which obviate the need to image such microscopic indentations. SFM, on the other hand, has been developed primarily as an imaging tool which depends on tip-surface interaction forces. Both of these methods depend on very low load mechanical contacts and can, in principle, be used to examine mechanical properties on a very fine, near atomic, dimensional scale. Indeed, efforts have been made to apply the technique of nanoindentation at ever smaller loads, while SFM-based techniques have been developed which enable one to assess mechanical properties. Nonetheless, approximately three orders of magnitude separate the commonly-used load ranges of these methods, and it is precisely in this load gap that one might like to work in order to investigate mechanical properties in the 1-10 nm regime. A review of recent work in this area is presented along with results obtained using SFM-based nanoindentation techniques on surfaces and thin coatings. Methods for interpreting the results of such experiments are evaluated, and some prospects for the future are outlined. (C) 1997 Elsevier Science S.A.