Indentation

Indentation

Indentation techniques have been used for many years and is conceptually very simple.   A tip, usually made of diamond, is forced down into the surface of the sample material and the area of the resulting of the impression measured.  Indentation is traditionally used as a method to evaluate the mechanical properties of materials such as hardness.  The hardness is simply the applied force divided by the resulting (projected) area. However,  conventional indentation involves the optical imaging of residual indent impressions which imposes a lower limit on the scale of testing.  This limit has been overcome in recent years by the development of nanoindentation.

Nanoindentation

Nanoindentation instruments are capable of continuously measuring  the indentation loads and displacements.  Indentation on a smaller scale is routinely achieved today by applying minute forces (usually mN) and by continuously measuring both the force and depth.  By combining the details of the force and indentation depth with a detailed knowledge of the tip shape and an understanding of the compliance of the indentation system, the mechanical properties of the sample can be calculated.

Nanoindentation is an ideal method for studying mechanical deformation in semiconductors since details of load-unload curves (see below) and hardness parameters can be directly correlated with the induced structural changes.  Spherical indentation is particularly suited to semiconductor studies as these materials are generally quite brittle and are prone to cracking at small loads.  The ANU has a ultra-micro indentation system (UMIS) which was designed and manufactured in Australia.