Electromechanical Characterization of Au Thin Films using Micro-tensile Testing

Abstract

This paper presents the test technique about measurement of electrical resistance changes of thin films during tensile testing. In this work, we used a real-time digital image correlation strain measurement system coupled with micro-tensile testing unit and voltage/current sourcemeter. This system has the advantage of real time displacement monitoring with a resolution of 50 nm during the micro-tensile testing, with the ability to measure the variation in electrical resistance of the specimen at the same time. We obtained the complete testing data for the stress-strain curve and associated electrical resistance-strain curve for 1 and 2 μm-thick freestanding gold films. Young's modulus was about 61~69 GPa and 0.2% offset yield strength was about 361~402 MPa. In case of the electrical resistance, rapid change was observed under the elastic regime, while less obvious under the plastic regime. We also conducted finite element analysis, and this result implied that the electrical resistivity would not be constant during micro-tensile testing.

Mechanical characterization of sub-100-nm-thick Au thin films by electrostatically actuated tensile testing with several strain rates

“…Lee et al reports the 0.2% yield strength of 361 to 402 MPa for the Au films having 1000 to 2000 nm. 17) The texture of the film determined in the fabrication process is likely to be the origin of these differences in the reported values of yield strengths of Au thin films.…”

“…11) In fact, the small Young's modulus of Au thin films compared to the bulk has been reported previously by several groups. [12][13][14][15][16][17] For example, Haque and Saif conducted the tensile tests of an Au film with a thickness of 350 nm fabricated by sputtering method. 14) They obtained the Young's modulus of 52 GPa.…”

Tensile testing of ultra-thin films on water surface

“…Therefore, the effect of any possible chemical reaction at the interface between the Au specimen and underlying water can be neglected. Moreover, the mechanical behaviour of free-standing Au thin films with thickness above 100 nm has been widely studied 15,[17][18][19][20][21] , which is useful for the validation of our tensile testing method. However, to the best of our knowledge, ultra-thin Au films with thickness below 100 nm have not been tested by the free-standing tensile test due to the difficulties in the specimen fabrication and handling without damage.…”

“…Furthermore, a gripping method using polymer-coated grips is devised to attach loading grips to the thin-film specimen by van der Waals adhesion. A digital image correlation (DIC) device is set up for real-time strain measurement 14,15 . In the end, we have been able to apply tensile force to the floated specimens and directly measure stress-strain curves, from which the mechanical properties of ultra-thin films can be obtained.…”