Browsing by Author "Ho, Pei-Jung"

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Facile electrochemical synthesis of 3D nano-architectured CuO electrodes for high-performance supercapacitors
(2014-08-28)
Deng, Ming-Jay
;
Wang, Cheng-Chia
;
Ho, Pei-Jung
;
Lin, Chih-Ming
;
Chen, Jin-Ming
With a simple electrochemical process, we prepared nano-architectured CuO electrodes with a 3D hierarchically porous structure and an excellent supercapacitive performance. These nano-architectured CuO electrodes were processed through co-deposition of a Ni-Cu layer on Ni foam, selective etching of Cu from the Ni-Cu film (leaving tentacle-like nanoporous Ni), and anodic deposition of CuO nanoribbons (NRs) on the tentacle-like nanoporous Ni/Ni foam substrate. Because of its unique nano-architecture, the prepared CuO nanoribbon-on-Ni-nanoporous/Ni foam (CNRNP) electrode shows exceptional performance of energy storage relative to a conventional version of the electrode. The CNRNP electrode has also a superior kinetic performance relative to CuO nanoflake-on-Ni foam (CNFNF) and flake-like CuO (FLC) electrodes. Besides its excellent cyclic stability, an exceptionally large specific capacitance of 880 and 800 F g(-1) (deducting the substrate capacitance from the total) for the CNRNP electrode is obtained at scan rates of 10 and 200 mV s(-1), respectively. The excellent pseudocapacitive characteristics of CNRNP electrodes associated with the variation of the Cu oxidation state during charge and discharge cycles were elucidated with in situ X-ray absorption near-edge structure (XANES) spectra.
Tailor magnetic order and spin-polarized gap states of opto-spintronic compounds by carrier mediation
(2018-08-15)
Yang, Chao-Yao
;
Chiu, Yi-Hsuan
;
Tsai, Kai-An
;
Hsu, Hua-Shu
;
Lin, Jun-Xiao
We investigate the role of carriers in the presence of oxygen vacancies (Vo) in mediating the ferromagnetic order and spin-polarized gap states of Cu-doped ZnO nanoparticles. We demonstrate the tuning of magnetic order via post-annealing under Ar/O-2. Carrier (Vo)-rich condition (Ar-treatment) is found to favor higher magnetic order of the nanoparticles with enhanced thermal stability and wide spin-polarized gap states from ultra-violet (UV) to visible energy range. Conversely, carrier (Vo)-poor condition (O-2-treatment) reduces resistance to thermal fluctuations and quenched spin-polarization due to lack of carrier mediation. The proposed method is effective to tailor the magnetic order as well as the wide polarized band-gap states, of oxide opto-spintronic compounds by finding the physical equivalency between charge carriers and spin electrons. (C) 2018 Elsevier B.V. All rights reserved.