Indenting thin films using an atomic force microscope

The feasibility of using a Scanning Probe Microscope to measure nanomechanical properties of thin films was investigated. An Atomic force Microscope was utilized in an attempt to perform nanoindentations to measure the hardness and elastic modulus of several materials. A high modulus cantilever beam was constructed from silicon and a tungsten bead was adhered to its free end. Using this cantilever assembly three samples were indented: a bulk aluminum sample, a 2micrometers thick aluminum film sputtered onto a glass substrate, and a elastomer (rubber band). Subsequent to the indenting process, force curves were captured in the form of tip deflection versus the z-displacement of the piezoelectric. Using transformation equations typical loading and unloading curves were generated from this data. The loading portion of the curves were used to generate the hardness of the materials, while the unloading portions of the curves were used to generate the material\u27s elastic modulus. Two analysis techniques are presented for use in the determination of the elastic modulus in conjunction with the type of unloading behavior exhibited. To asses the accuracy of the methods used, the values of hardness and elastic moduli for several materials were calculated and compared to available literature values determined by independent means. The results demonstrate that with the construction of a stiff cantilever assembly and with the proper analysis of good force curves, the potential of obtaining hardness and elastic moduli for thin film materials, via an AFM, is feasible