Mechanical characterization of nickel nanowires by using a customized atomic force microscope

A new experimental method to characterize the mechanical properties of metallic nanowires is introduced. An accurate and fast mechanical characterization of nanowires requires simultaneous imaging and testing of the nanowires. However, existing mechanical characterization techniques fail to accomplish this goal due either to the lack of imaging capability of the mechanical test setup or the difficulty of individual alignment and manipulation of single nanowires for each test. In this study, nanowire specimens prepared by an electroplating technique are located on a silicon substrate with trenches. A customized atomic force microscope is located inside a scanning electron microscope (SEM) in order to establish the visibility of the nanowires, and the tip of the atomic force microscope cantilever is utilized to bend and break the nanowires. The ability to visualize the nanowires in an SEM improves the speed and accuracy of the tests. Experimentally obtained force versus bending displacement curves are fitted into existing analytical formulations to extract the mechanical properties. Experimental results reveal that nickel nanowires have significantly higher strengths than their bulk counterparts, although their elastic modulus values are comparable to bulk nickel modulus values.