In situ electron microscopy four-point electromechanical characterization of freestanding metallic and semiconducting nanowires

Electromechanical coupling is a topic of current interest in nanostructures, such as metallic and semiconducting nanowires, for a variety of electronic and energy applications. As a result, the determination of structure-property relations that dictate the electromechanical coupling requires the development of experimental tools to perform accurate metrology. Here, a novel micro-electro-mechanical system (MEMS) that allows integrated four-point, uniaxial, electromechanical measurements of freestanding nanostructures in-situ electron microscopy, is reported. Coupled mechanical and electrical measurements are carried out for penta-twinned silver nanowires, their resistance is identified as a function of strain, and it is shown that resistance variations are the result of nanowire dimensional changes. Furthermore, in situ SEM piezoresistive measurements on n-type, [111]-oriented silicon nanowires up to unprecedented levels of ∼7% strain are demonstrated. The piezoresistance coefficients are found to be similar to bulk values. For both metallic and semiconducting nanowires, variations of the contact resistance as strain is applied are observed. These variations must be considered in the interpretation of future two-point electromechanical measurements. Electromechanical measurements are demonstrated in silicon and silver nanowires using a newly developed MEMS for in situ electron microscopy, four-point electromechanical characterization. Silver nanowires show resistance changes in agreement with elasticity and plasticity theory, while silicon nanowires, strained up to 7%, show piezoresistance coefficients in the same order of magnitude as bulk. Strain-induced variations in the contact resistance are also identified.