calculated projected pile up. This is taken from the equations from the nanoindenter [1], and is plotted as a reference. The pile up area is less than this projected area, and if the two were to be added, it would be the total area. Although others have tried to use this total area values, the plot clearly shows that pile up is not affected by film thickness. No matter the depth of the indent, the pile up will be the same in all cases. 1.4 Conclusions Overall, this work first concludes that SEM images and the software ImageJ can be used to measure the pile up of the indents. This replaces tedious methods such as atomic force microscopy. The next conclusion is that there is no effect on pile up with changing the thickness of gold films on silicon substrates. Other substrates and films are being studied (MgO, Al2O3, AlN), and the same trend is appearing across combinations that provide pile up. Instead of having to worry about accounting for pile up, elastic properties can be considered the same as if there were no pile up. The model seemed to account for the pile up, but when measuring and calculating the trends, the pile up instead has no effect on the elastic properties of the material. These findings will help shape the way that the elastic modulus is measured for soft films on hard substrates where pile up occurs. It is greatly important to extract the film properties correctly so that material selection during thin film applications can happen without errors. References 1. Oliver WC, Pharr GM (1992) An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J Mater Res 7:1564–1583 2. Oliver WC, Pharr GM (2004) Measurement of hardness and elastic modulus by instrumented indentation: advances in understanding and refinements to methodology. J Mater Res 19:3–20 3. Chen X, Vlassak JJ (2001) Numerical study of the measurement of thin film mechanical properties by means of nanoindentation. J Mater Res 16:2974–2982 4. Doerner MF, Nix WD (1986) A method for interpreting the data from depth-sensing indentation instruments. J Mater Res 1:601–609 5. Gao H, Chiu C-H, Lee J (1992) Elastic contact versus indentation modelling of multi-layered materials. Int J Solid Struct 29:2471–2492 6. Zhou B, Prorok B (2010) A discontinuous elastic interface transfer model of thin film nanoindentation. Exp Mech 50:793–801 7. Zhou B, Prorok BC (2010) A new paradigm in thin film nanoindentation. J Mater Res 25:1671–1678 8. Kese K, Li ZC (2006) Semi-ellipse method for accounting for the pile-up contact area during nanoindentation with the Berkovich indenter. Scr Mater 55:699–702 9. Kese K, Rowcliffe DJ (2003) Nanoindentation method for measuring residual stress in brittle materials. J Am Ceram Soc 86:811–816 1 Newly Discovered Pile Up Effects During Nanoindentation 5
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