| Recent developments in the field of nanotechnology and nanofabrication have produced material structures with nanometer-scale dimensions. However, the practical applications of these structures requires a thorough understanding of their mechanical properties on the nanometer scale. When used in an indentation mode, the atomic force microscope (AFM) is capable of probing mechanical properties with unprecedented spatial and force resolution. Until recently, routine extraction of quantitative data from AFM nanoindentation measurements had not been possible.; A custom-built AFM has been developed at the Naval Research Laboratory (NRL) to quantitatively probe mechanical properties at the nanometer scale. The present study describes the design, operation, and calibration of this instrument. A serious hysteresis and creep effect associated with lead zirconate titanate (PZT) piezoelectric ceramics used in this and many other AFM designs, which can significantly limit the potential of the AFM in being used as a quantitative mechanical property probe, has been observed. This effect has been eliminated by replacing the sample PZT with an electrostrictive lead magnesium niobate (PMN) component.; Upon making this improvement, the capability of the AFM to probe mechanical properties at the nanometer scale is shown for three single-crystal metals (chromium, molybdenum, and tungsten) and their respected native oxides. Nanoindentation data were compared with the measured thicknesses of the metallic layers obtained using X-ray Photoelectron Spectroscopy (XPS).; To further investigate the effects of oxide layers on the surface mechanical properties, nanoindentation was performed on silicon single crystals with native oxide and thermally-grown surface oxide layers of 5, 15, and 30 nm thicknesses. Nanoindentation data were correlated with preliminary modeling results obtained using finite element analysis (FEA).; Using micron sized soda lime glass spherical indenters, absolute quantitative mechanical property measurements of highly oriented pyrolytic graphite (HOPG), polycarbonate, and polystyrene films were obtained. Nanoindentation data were compared for each sample using a commercial indentation instrument.; Conclusions as well as recommendations outlining necessary effects which should be of concern when performing nanoindentation via atomic force microscopy are given. |
