Browsing by Author "Koike, Junichi"

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Conformal Deposition of RuO2 on Cu via a Galvanic Cementation Reaction
(2019-06-28)
Lin, Chun
;
Chou, Shih-Cheng
;
Tso, Kuang-Chih
;
Hsieh, Yi-Chieh
;
Chan, Ting-Shan
We develop a seedless wet chemical process to deposit uniform RuO2 on a Cu substrate. Our approach entails the synthesis of volatile RuO4 colloids in a pH 9 aqueous solution from the oxidation of RuCl52- by ClO-, followed by a galvanic cementation reaction in which the Cu undergoes a mild oxidation in conjunction with the reduction of RuO4 to produce a dense and conformal RuO2 thin film on the Cu surface. The nature for the chemical reactions and constituents involved are investigated by UV-Vis, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Both as-deposited and annealed RuO2 films are characterized by scanning electron microscope and X-ray diffractometer. The as-deposited RuO2 film, with a thickness of 199 nm, reveals an amorphous structure and after an Ar annealing, becomes crystalline in rutile phase. In between the RuO2 and Cu, there are presence of CuO from the displacement cementation reaction, and Cu2O from the parasitic Cu corrosion as expected from the Pourbaix diagram. These Cu oxides, with a thickness of 330 nm, provide sufficient adhesive bonding between RuO2 and Cu. (c) The Author(s) 2019. Published by ECS.
Polydopamine and Its Composite Film as an Adhesion Layer for Cu Electroless Deposition on SiO2
(2020-03-09)
Chou, Shih-Cheng
;
Chung, Wei-An
;
Fan, Tzu-Ling
;
Dordi, Yezdi
;
Koike, Junichi
We explore dopamine (DA) and its mixtures with polyethylene glycol (PEG) or polyethylenimine (PEI) as an adhesion layer for bonding between Cu and SiO2. The DA is oxidized to form polydopamine (PDA) which deposits as aggregates on SiO2 surface with notable surface roughness. After mixing with PEG or PEI, the morphology of PDA aggregates is altered considerably. Electroless Cu deposition in a mild alkaline bath is employed to deposit Cu atop the adhesion layer. The Cu films reveal an fcc lattice with (111) preferred orientation and their thickness was around 650 nm. From measurements of four-point probe, breaking strength, and tape-peeling tests, the PDA/PEG mixture reveals impressive performance serving as a strong adhesive for robust Cu bonding. We attribute the unique adhesive ability of PDA/PEG to the hydrogen bonds established between the catechol and amine groups of DA with PEG that renders desirable film formation on the SiO2 surface for optimized interaction between Cu and SiO2. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.