Thin metallic films are commonly employed in micro and nano electro mechanical systems (MEMS & NEMS). These films may experience various mechanical constraints. The design of more reliable and sophisticated devices relies on the knowledge, understanding and ability to control the mechanical properties of thin films. A main characteristic of thin films is that the specimen dimensions become comparable to the characteristic length-scales that govern the mechanical behavior. Therefore, specimens at the sub-µm scales often exhibit a mechanical behavior which may be different from that of bulk specimens. This phenomenon is referred to as "size effect". The difficulties in producing and handling µm-scale free-standing specimens led to the development of several methods for studying the mechanical behavior of such films. However, this mechanical behavior is significantly influenced by many factors, such as the film substrate, deposition method and fabrication process of the test device. Tensile test of free standing films eliminate the effect of the substrate. Moreover, the stress and strain states are uniform during the tensile test, which simplifies the extraction of the mechanical properties of the specimen. In this talk we present a novel apparatus and a procedure for tensile testing of thin free-standing films under a wide range of strain rates from quasistatic to high, almost comparable with those obtained in Hopkinson bar tests. Results from tensile tests of thin aluminum films under quasi-static, medium and high strain rates are demonstrated. A large strain rate effect is revealed as the ultimate tensile strength increases by more than 400% compared to quasi-static tests. An analysis of the kinetic relation for plastic flow shows that all commonly used kinetic laws cannot explain our results. Instead, we suggest an elaborated kinetic law that is in good agreement with the results over the entire range of strain rates.
