Murray lecture tensile testing at the micrometer scale: Opportunities in experimental mechanics

The measurement of mechanical properties using specimens whose minimum dimensions are of the order of micrometers is an important new area of experimental solid mechanics. One obvious application is in the area of micro-electromechanical systems (MEMS) where the final product is on the millimeter or micrometer scale. This paper describes techniques developed at Johns Hopkins University for tensile testing of materials used in MEMS. Polycrystalline silicon is currently the most widely used material; its modulus has been measured as 158±10 GPa, and its Poisson's ratio as 0.22±0.01, with fracture strengths ranging from 1.2 to 3.0 GPa depending upon the manufacturer. The properties of silicon nitride, silicon carbide, and electroplated nickel have also been measured and are presented. In addition to the quasi-static tensile tests, new techniques and procedures for measuring strengths at stress concentrations in brittle thin-film materials, fatique testing, and high-temperature testing are described.