Study of uniaxial deformation behavior of 50 nm-thick thin film of gold single crystal using in situ X-ray pole figure measurements

In this paper, in situ measurements of synchrotron x-ray pole figure have been performed during incremental uniaxial deformation test on a single-crystal gold foil. The 50 nm thick Au thin film was elaborated by ion sputtering at 400 °C on NaCl single crystal as a template. The resulting film consists of a single-crystal gold foil containing a small density of thin and small {111} growth twins (few nm thick and few tens of nm long) revealed by x-ray pole figure measurement. The as-deposited gold single crystal was then transferred onto flexible polyimide substrates for deformation test. This work focuses on the relative evolution of the diffracting volume related to growth twins during a loading-unloading tensile test. Macroscopic applied deformations and x-ray pole figures were measured in situ during a uniaxial tensile test in the Au [110] direction. X-ray pole figures clearly evidenced the relative evolution of the diffracting volumes related to the (111) and 1¯1¯1 twins which exhibit a huge increase of about 450% at a uniaxial applied true strain of about 4%. The concomitant variation of diffracting volumes related to the two other twin variants (namely 1¯11 and 11¯1 twins) shows a relatively low decrease of 25%. The results open out onto a true strain-twinning volume hysteresis curve, indicative of the deformation mechanisms of gold thin films that can be interpreted as a twinning-detwinning mechanism.