Abstract
Hierarchical structures of 20 nm grains embedded with twins are realized in electrodeposited Au–Cu alloys. The electrodeposition method allows refinement of the average grain size to 20 nm order, and the alloying stabilizes the nanoscale grain structure. Au–Cu alloys are face-centered cubic (FCC) metals with low stacking fault energy that favors formation of growth twins. Due to the hierarchical structure, the Hall–Petch relationship is still observed when the crystalline size (average twin space) is refined to sub 10 nm region. The yield strength reaches 1.50 GPa in an electrodeposited Au–Cu alloy composed of 16.6 ± 1.1 nm grains and the average twin spacing at 4.7 nm.
Highlights
The usage of precious metals in micro-components of microelectromechanical system (MEMS)devices has been demonstrated to allow further enhancement in the sensitivity and miniaturization of the device [1,2,3]
Electrodeposited Au–Cu alloys incorporated with nanotwins were confirmed by scanning transmission electron microscopy (STEM) and HRTEM observation
To understand the stress drop observed in the stress–strain curves, microstructures of the deformed micro-pillars were further investigated by the STEM and HRTEM
Summary
The usage of precious metals in micro-components of microelectromechanical system (MEMS)devices has been demonstrated to allow further enhancement in the sensitivity and miniaturization of the device [1,2,3]. The usage of precious metals in micro-components of microelectromechanical system (MEMS). Au is a promising material owing to its advantageous properties and process feasibility in electronic devices [4]. An improved yield strength (σy ) of ~500 MPa [5] has been reported by refining the average grain size (d) to nanoscale following the Hall–Petch relationship (HP) [6,7,8], the strength is still low when compared with materials commonly used in electronic devices. Silicon materials are often applied in MEMS devices and possess fracture strength of 1–3 GPa [9]. Enhancement in the strength along with the grain refinement reverses when the average grain size reaches ca
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