Nano-Scale Indentation Creep Testing at Non-Ambient Temperature

Abstract

Depth sensing nanoindentation can be used to study the time-dependent deformation of very small volumes of materials, contacts, and thin films. Force modulation provides a continuous measure of the contact stiffness during an indentation, and minimises the adverse effect of thermal drift which is particularly important for sub-micron samples. Most of the nanoindentation experimental work so far has been carried out at room temperature. In this paper we describe a solid-state thermoelectric heating and cooling system which gives a straightforward way to vary the temperature of both sample and tip. The capabilities of the technique are demonstrated by observing the time and temperature dependent creep properties of high purity Indium. Hardness, its strain rate dependence, the stress exponent, and the activation energy for the creep process can all be directly measured from nanometre scale contacts, and the values obtained are similar to those from bulk conventional creep testing. The technique is likely to be of particular value for polymer thin films.

Key Words:

• Nanoindentation
• creep
• sub-micron testing
• hardness
• strain rate
• activation energy