A note on the reliability of nanoindentation: Effect of sample standing

This paper discusses the experimental reliability in carrying out nanoindentationson a generally-purposed nanoindentation facility using a stage with magnet buttons for sample holding. The instability of the testing results was found to happen during the nanoindentation on both silicon and quartz samples bonded on different types of stands. It was detected that the maximum indentation depth under the same load function could deviate considerably when such a sample was positioned beyond a certain distance from the centre of a magnet button. It was identified that the application of a thin sample stand led to large deviations, and that using a thick stand would provide more reliable measurements. The most reliable outcome was found to be associated with the testing on the sample directly waxed to the indentation stage without using a sample stand. A systematic analysis revealed that such instability of nanoindentation was caused by the improper contact between a sample stand and the indentation stage, including the insufficient bending rigidity of the stand. It was concluded that a simple solution tothis technical problem is to use a thick enough stand of high bending rigidity and to guarantee a stable contact with the stage surface to obtain sufficient mechanical support to the nanoindentation. This study alerts to the fact that even though the force and deformation in a nanoindentation test are small, the effect of the mechanical support to a sample on the reliability of the testing result can be significant.