Browsing by Author "Tso, Kuang-Chih"

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Combination of electrophoresis and electro-flocculation for the formation of adhering IrO2 pH sensing films
(2019-07-20)
Wang, Han-Yi
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Hsieh, Yi-Chieh
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Tso, Kuang-Chih
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Chang, Chung-Kai
;
Cheng, Yu-Ting
We demonstrate a simple scheme to produce dense and adhering IrO2 thin films on ITO substrates via a bipolar pulsing process combining both electrophoresis and electro-flocculation. Our fabrication steps entail the synthesis of negatively-charged IrO2 nanoparticles in size of 3.5 nm using NaClO as an oxidizer in conjunction with Na3IrCl6, citric acid, and NaOH. Subsequently, multiple bipolar potentiostatic pulses are imposed in which alternating positive and negative potentials engender the electrophoresis of IrO2 nanoparticles, followed by their immediate coalescence facilitated by proton-catalyzed electro-floccu-lation. The resulting IrO2 thin films reveal impressive physical properties in surface uniformity, robust structural integrity, and strong adhesion to the substrate. The as-synthesized IrO2 thin film exhibits an amorphous nature with a pH sensing slope between -73.6 and -71.5 mV/pH, characteristic of super-Nernstian behavior. In contrast, the annealed IrO(2 )sample demonstrates a crystalline rutile phase with a pH sensing slope between -49.5 and -54.7 mV/pH, consistent with typical Nernstian response. Our approach provides a new route for the formation of strong and adhering oxide films from their colloidal constituents. (C) 2019 Elsevier Ltd. All rights reserved.
Conformal Deposition of RuO2 on Cu via a Galvanic Cementation Reaction
(2019-06-28)
Lin, Chun
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Chou, Shih-Cheng
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Tso, Kuang-Chih
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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.
Development of IrO2 bio-ink for ink-jet printing application
(2019-09-01)
Hsieh, Yi-Chieh
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Wang, Han-Yi
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Tso, Kuang-Chih
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Chang, Chung-Kai
;
Chen, Chi-Shih
We develop a chemical formulation to synthesize stable IrO2 colloidal solution as a bio-ink for ink-jet printing purpose. This wet chemical process entails Na3IrCl6 and NaClO as the Ir precursor and oxidizer, respectively. In addition, citric acid and sodium hydroxide are employed as the complex agent and pH adjuster. The pH value of the IrO2 colloidal solution could be readily adjusted over a broad range without incurring undesirable precipitation. Their respective zeta potential decreases from positive to negative with increasing pH values. The IrO2 colloidal solution demonstrates impressive chemical stability over extended storage at 5 and 65 degrees C. Images from transmission electron microscope indicate the average size for the IrO2 nanoparticles to be 3.5 nm. The X-ray diffraction pattern from the heat-treated IrO2 sample shows a polycrystalline rutile phase. The IrO2 colloidal solution undergoes repeated filtering and washing to retrieve the IrO2 nanoparticles. After an annealing at 450 degrees C for 2 h in air, the crystalline IrO2 nanoparticles are resuspended in a 0.5 wt% aqueous medium as the bio-ink for ink-jet printing on an ITO substrate. Our method enables the synthesis of stable IrO2 nanoparticles in a neutral solution at 25 degrees C, which provides a facile and effective approach over conventional ones that require alkaline environment at elevated temperature.
Facile Synthesis of Co3O4@CoO@Co Gradient Core@Shell Nanoparticles and Their Applications for Oxygen Evolution and Reduction in Alkaline Electrolytes
(2020-06-01)
Chou, Shih-Cheng
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Tso, Kuang-Chih
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Hsieh, Yi-Chieh
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Sun, Bo-Yao
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Lee, Jyh-Fu
We demonstrate a facile fabrication scheme for Co3O4@CoO@Co (gradient core@shell) nanoparticles on graphene and explore their electrocatalytic potentials for an oxygen evolution reaction (OER) and an oxygen reduction reaction (ORR) in alkaline electrolytes. The synthetic approach begins with the preparation of Co(3)O(4)nanoparticles via a hydrothermal process, which is followed by a controlled hydrogen reduction treatment to render nanoparticles with radial constituents of Co3O4/CoO/Co (inside/outside). X-ray diffraction patterns confirm the formation of crystalline Co(3)O(4)nanoparticles, and their gradual transformation to cubic CoO and fcc Co on the surface. Images from transmission electron microscope reveal a core@shell microstructure. These Co3O4@CoO@Co nanoparticles show impressive activities and durability for OER. For ORR electrocatalysis, the Co3O4@CoO@Co nanoparticles are subjected to a galvanic displacement reaction in which the surface Co atoms undergo oxidative dissolution for the reduction of Pt ions from the electrolyte to form Co3O4@Pt nanoparticles. With commercial Pt/C as a benchmark, we determine the ORR activities in sequence of Pt/C > Co3O4@Pt > Co3O4. Measurements from a rotation disk electrode at various rotation speeds indicate a 4-electron transfer path for Co3O4@Pt. In addition, the specific activity of Co3O4@Pt is more than two times greater than that of Pt/C.
Formation of Cu/MnOx composite film by concurrent electroplating and electrophoresis in an organic solvent
(2018-08-30)
Chiang, Wei-Shen
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Huang, Jun-Qian
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Tso, Kuang-Chih
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Hung, Pei-Sung
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Chen, Po-Chun
A composite Cu/MnOx thin film was fabricated by conducting electroplating of Cu and electrophoresis of MnOx colloids simultaneously in an organic electrolyte. The organic electrolyte was prepared by dissolving copper (II) acetylacetonate and manganese (II) acetylacetonate in ethylene glycol, with addition of 10 vol% acetic acid to improve ionic conductivity. Since both Cu ions and MnOx colloids carry positive charges, the formation of a composite film was achieved by a pulse current mode in which a low current pulse was used for Cu2+ reduction, followed by a high current pulse for the electrophoresis of the MnOx colloids. The Cu/MnOx composite film was dense and its X-ray diffraction pattern revealed a mixture of Cu, Mn2O3, and Mn3O4. Both X-ray photoelectron spectroscopy and X-ray absorption spectroscopy show consistent results confirming the metallic nature of Cu and oxidized state of Mn.
Interface Engineering Strategy Utilizing Electrochemical ALD of Cu-Zn for Enabling Metallization of Sub-10 nm Semiconductor Device Nodes
(2019-08-28)
Joi, Aniruddha
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Venkatraman, Kailash
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Tso, Kuang-Chih
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Dictus, Dries
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Dordi, Yezdi
A novel interface engineering approach, utilizing electrochemical atomic layer deposition (e-ALD) of Cu(Zn) on a Ru liner, is presented for enabling the metallization of sub-10 nm interconnects in future semiconductor devices. Upon thermal treatment, Zn present in the e-ALD Cu layer at similar to 0.8 at.% is shown to diffuse through the Ru liner and react with the SiO2 to form a Zn-silicate layer at the Ru-SiO2 interface. This 'self-forming' interfacial layer provides adhesion enhancement to the Ru-SiO2 interface and serves as a diffusion barrier retarding Cu diffusion into the SiO2 layer while enabling void-free gap-filling of high aspect ratio trench structures. Absorption Near-Edge Spectroscopy and Extended X-ray Absorption Fine Structure analyses confirm that the self-formed barrier layer is composed primarily of Zn2SiO4. The interface engineering approach utilizing Cu(Zn) presented herein offers several potential advantages over traditional Mn-based self-forming barrier approaches, i.e., scalability to narrower dimensions and minimal impact to interconnect resistance. (C) The Author(s) 2019. Published by ECS.
Synthesis and characterization of iridium oxide thin film via a pre-coordination step for bio-stimulating electrode application
(2020-08-01)
Chung, Tsai-Wei
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Hsieh, Ming-Ting
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Tso, Kuang-Chih
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Kuo, Shuo-Hsiu
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Cheng, Chien-Tai
An effective solution-based process is developed for the fabrication of iridium oxide thin film in application of bio-stimulating electrode. The chemical bath employs a pre-coordination scheme in which the IrCl63- precursor undergoes a ligand exchange step to form stable Ir(OH)(6)(3-), followed by an oxidative electroless deposition to render iridium oxide thin film with desirable surface morphologies. Relevant processing parameters have been optimized to increase the utilization rate of Ir precursor for a thicker deposit without any noticeable defect. The iridium oxide thin film is mechanically robust and exhibits superior performances in both charge storage capacity and charge injection capacity. In particular, the normalized charge storage capacity is recorded at 0.367 mC/(cm2hm), a value that is five times greater than comparable iridium oxide thin films. In addition, in cell viability test, the iridium oxide thin film demonstrates impressive biocompatibility with desirable growth of neuronal cells.
Synthesis of IrO(2)decorated core-shell PS@PPyNH(2)microspheres for bio-interface application
(2020-09-11)
Hsieh, Tsung-Lin
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Hung, Pei-Sung
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Wang, Chuan-Jyun
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Tso, Kuang-Chih
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Wang, Han-Yi
In this paper, an effective approach is demonstrated for the fabrication of IrO2-decorated polystyrene@functionalized polypyrrole (core@shell; PS@PPyNH2) microspheres. The synthesis begins with the preparation of monodispersive PS microspheres with a diameter of 490 nm, by a process of emulsifier-free emulsion polymerization, followed by a copolymerization process involving pyrrole and PyNH(2)monomers in a PS microsphere aqueous suspension, to produce uniform PS@PPyNH(2)microspheres with a diameter of 536 nm. The loading of 2 nm IrO(2)nanoparticles onto the PS@PPyNH(2)microspheres can be easily adjusted by tuning the pH value of the IrO(2)colloidal solution and the PS@PPyNH(2)suspension. At pH 4, we successfully obtain IrO2-decorated PS@PPyNH(2)microspheres via electrostatic attraction and hydrogen bonding simultaneously between the negatively-charged IrO(2)nanoparticles and the positively-charged PS@PPyNH(2)microspheres. These IrO2-decorated PS@PPyNH(2)microspheres exhibit a characteristic cyclic voltammetric profile, similar to that of an IrO(2)thin film. The charge storage capacity is 5.19 mA cm(-2), a value almost five times greater than that of PS@PPyNH(2)microspheres. In addition, these IrO2-decorated PS@PPyNH(2)microspheres exhibit excellent cell viability and biocompatibility.