title: Nano-volcanic Eruption of Silver.
abstract: Silver (Ag) is one of the seven metals of antiquity and an important engineering material in the electronic, medical, and chemical industries because of its unique noble and catalytic properties. Ag thin films are extensively used in modern electronics primarily because of their oxidation-resistance. Here we report a novel phenomenon of Ag nano-volcanic eruption that is caused by interactions between Ag and oxygen (O). It involves grain boundary liquation, the ejection of transient Ag-O fluids through grain boundaries, and the decomposition of Ag-O fluids into O2gas and suspended Ag and Ag2O clusters. Subsequent coating with re-deposited Ag-O and the de-alloying of O yield a conformal amorphous Ag coating. Patterned Ag hillock arrays and direct Ag-to-Ag bonding can be formed by the homogenous crystallization of amorphous coatings. The Ag "nano-volcanic eruption" mechanism is elaborated, shedding light on a new mechanism of hillock formation and new applications of amorphous Ag coatings.
authors.affiliation: Department of Materials Science and Engineering, National Cheng Kung University, Tainan, 70101, Taiwan.|Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan, 70101, Taiwan.
authors.forename: Shih-Kang
authors.initials: SK
authors.lastname: Lin
authors.affiliation: Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, Japan.|Department of Adaptive Machine Systems, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, Japan.
authors.forename: Shijo
authors.initials: S
authors.lastname: Nagao
authors.affiliation: Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, Japan.
authors.forename: Emi
authors.initials: E
authors.lastname: Yokoi
authors.affiliation: Department of Adaptive Machine Systems, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, Japan.
authors.forename: Chulmin
authors.initials: C
authors.lastname: Oh
authors.affiliation: Department of Adaptive Machine Systems, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, Japan.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Materials Science and Engineering, National Cheng Kung University, Tainan, 70101, Taiwan.
authors.forename: Yu-Chen
authors.initials: YC
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, National Cheng Kung University, Tainan, 70101, Taiwan.
authors.forename: Shih-Guei
authors.initials: SG
authors.lastname: Lin
authors.affiliation: Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, Japan.|Department of Adaptive Machine Systems, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, Japan.
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Suganuma