# The hardness and modulus of molybdenum/aluminum oxide microlaminates as determined by nanoindentation

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 Title: The hardness and modulus of molybdenum/aluminum oxide microlaminates as determined by nanoindentation McAdams, Shaun Donald Pharr, George M. The elastic modulus and hardness of 1.2 $\mu$m thick films made of alternating and equal layers of sputter deposited Mo and Al$\sb2$O$\sb3$ were measured by a depth-sensing indentation apparatus which can test the properties of submicron volumes of material. Microlaminates with bilayer thicknesses ($\lambda$) of 5, 20, 30, and 100 nm were prepared and tested. The moduli of the microlaminates were found to follow a rule-of-mixtures. No "supermodulus effect" was observed. The hardness of the 100 nm microlaminate was observed to be almost twice as high as the hardness of either as-deposited Mo or Al$\sb2$O$\sb3$. This may be evidence of the "superstrength effect." A new method for determining the area of contact between an indenting diamond and the tested sample as a function of the plastic depth of indentation was established. An accurate area function is necessary for deriving mechanical properties from indentation data. McAdams, Shaun Donald. (1991) "The hardness and modulus of molybdenum/aluminum oxide microlaminates as determined by nanoindentation." Masters Thesis, Rice University. http://hdl.handle.net/1911/13535. http://hdl.handle.net/1911/13535 1991