New ultra low load indentation device with extremely low thermal drift: principle and experimental results

Nanoindentation has become an indispensable method for measuring the mechanical properties of small volumes of materials. It has gained importance in several domains such as thin film science, electronics and materials research. Despite continuous evolution of the nanoindentation technique over the past fifteen years, contemporary methods still suffer serious drawbacks, particularly long thermal stabilization and thermal drift which limit the duration of the measurements to only a short period of time. The presented paper introduces a novel ultra nanoindentation method that utilizes loads from the μN range up to 50 mN, is capable of performing long term stable measurements and has negligible frame compliance. The method is based on a novel patented design which uses an active top referencing system and components made from Zerodur$^{\circledR}$ glass. Several materials including fused silica, DLC and selected polymers were used to show the performance of the method. The tests were performed mainly at low loads to demonstrate the low load and displacement capabilities of the instrument. A large number of tests were performed with a hold at the maximum indentation load to observe the instrument thermal drift. It was proved that indentations with maximum loads in μN range and penetration depth of a few nm can be easily performed with this method. The measurements with hold at maximum load confirm extremely low levels of instrument thermal drift. The presented Ultra Nanoindentation Tester opens new possibilities for testing thin films and long term testing including creep of polymers at very high resolution without the need of long thermal stabilization