Elastic modulus measurements by force spectroscopy
NanoScan scanning nanohardness testers are capable of measuring the quantitative value of elastic modulus by the force spectroscopy technique . This method consists in the oscillating the probe sensor simultaneously with loading. The oscillation amplitude is less 10 nm, frequency is around 10 kHz. When the diamond indentor is in contact with the surface, the frequency increases with increasing load.
According to the analytical description based on the Hertz model, the slope of the frequency dependence versus probe displacement (approach curve) is proportional to the elastic modulus of the material in the area of contact. Before the test, the device is calibrated on reference materials with known elastic modulus values. The resulting elastic modulus value is evaluated as a proportion between approach curves slopes and reference elastic modulus.
|The slope of ∆f curve characterizes the elastic modulus of the material.||Approach curve measurement schema.|
This method is nondestructive and allows measuring elastic modulus values in the range up to 1000 GPa. The material layer involved in the test can be as small as 100 nm. This makes it possible to measure the elastic modulus of thin films without substrate influence.
The comparative measurements on different materials showed correct elastic modulus values in the wide range.