Novel ultra nanoindentation method with extremely low thermal drift: Principle and experimental results

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Novel ultra nanoindentation method with extremely low thermal drift: Principle and experimental results J. Nohava CSM Instruments SA, Rue de la Gare 4, Peseux CH-2034, Switzerland

N.X. Randalla) CSM Instruments Inc., Needham, Massachusetts 02494

N. Conte´ CSM Instruments SA, Rue de la Gare 4, Peseux CH-2034, Switzerland (Received 24 July 2008; accepted 20 October 2008)

Despite active development over the past 15 years, contemporary nanoindentation 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 work introduces a novel ultra nanoindentation method that uses loads from the mN 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. Several materials were used to demonstrate the performance of the 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 high resolution without the need of long thermal stabilization.

I. INTRODUCTION

Recent advances in materials research have motivated the development of nanoindentation instruments using extremely low loads and depths. Several such instruments have been proposed to answer this need. These instruments allow the use of loads from several tens of mN up to several mN and can measure depth within a few nm up to a few hundreds of nm. Once such low loads and penetration depths are applied and measured, appropriate working conditions must be ensured. Nanoindentation machines are generally placed in a soundproof enclosure on an antivibration table to eliminate the transfer of vibrations and noise to the displacement and load signals. Of great importance is the thermal stability of the environment: the temperature variation should not exceed 0.5  C/h. This criterion is crucial for nearly all presently commercially available instruments as they all suffer, to some degree, the problem of thermal drift.1–3 The phenomenon of thermal drift is well known in the nanoindentation field and significantly limits the use of such instruments for longterm measurements. Although the term “thermal drift” has never been properly defined, it is widely understood as “the change in the indentation depth when the force on the indenter is maintained constant and the a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0127 J. Mater. Res., Vol. 24, No. 3, Mar 2009

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material does not exhibit time-dependent mechanicalproperties.” Materials that do not exhibit timedependent properties do not change their deformation in time while constant load is applied. The thermal

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