Tensile behavior of nanotwinned nanoporous gold

Abstract

Nanoporous gold(np-Au) have been widely studied for catalyst, sensor, actuator and other applications due to their high surface-to-volume ratio, bio-compatibility and chemical inertness. Np-Au shows brittle fracture by open cell structure that only few of ligament should bear tensile load. Brittleness of np-Au causes difficulty in use to MEMS devices and other applications, thereby mechanical properties of np-Au have been investigated. In recent studies, nanotwin(nt) structure in Cu and Ag can significantly enhance both strength and ductility compared to ultra-fine grain or coarse grain structure due to a large density of twin boundaries. In this study, we fabricated nanotwined nanoporous gold(nt np-Au) thin film and measured its mechanical properties using in-situ tensile test. We fabricated nt Ag-Au thin film by co-sputtering of Ag and Au targets in magnetron sputter. By changing annealing time after deposition, we controlled grain size and twin boundary density in nt precursor thin film. After free corrosion dealloying in nitric acid, microstructures of precursor and np-Au are observed by TEM(Transmission Electron Microscope) and SEM(Scanning Electron Microscope) and mechanical properties are investigated by in-situ tensile test using push-to-pull device in SEM chamber.