Browsing by Author "Wan, Chung-Yun"

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Annealing effect on the photoluminescence characteristics of ZnO-nanowires and the improved optoelectronic characteristics of p-NiO/n-ZnO nanowire UV detectors
(2015-06-01)
Li, Yu-Ren
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Wan, Chung-Yun
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Chang, Chia-Tsung
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Huang, Yu-Chin
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Tsai, Wan-Lin
Transparent ultraviolet (UV) detectors with nanoheterojunctions (NHJs) of p-type NiO and n-type ZnO nanowires (ZnO-NWs) were successfully fabricated using a DC sputtering system and a hydrothermal process, respectively. After annealing in nitrogen ambient, the near-band-edge emission to deep level emission ratio (NBE/DLE) of ZnO-NWs gradually increased as the temperature increased and reached a maximum of 28.9 at a temperature setting of 500 degrees C. In contrast, after annealing in oxygen atmosphere, the NBE/DLE of ZnO-NWs initially increased from 1.2 to 5.9 and then decreased to 3.2. At a reverse bias of 2V, the devices with the 500-degrees C-N-2-annealed ZnO-NWs exhibited better sensitivity (J(UV)/J(Dark) = 5.65; J(Visible)/J(Dark) = 1.35) to UV light (365 nm, 0.3 mW/cm(2)) than those with the as-grown ZnO-NWs (J(UV)/J(Dark) = 4.98; J(Visible)/J(Dark) = 3.82) because the structural defects in ZnO-NWs were effectively eliminated after annealing in nitrogen ambient at 500 degrees C. (C) 2015 The Japan Society of Applied Physics
High-Performance Programmable Metallization Cell Memory With the Pyramid-Structured Electrode
(2013-10-01)
Huang, Yu-Chih
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Tsai, Wan-Lin
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Chou, Chia-Hsin
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Wan, Chung-Yun
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Hsiao, Ching
The pyramid structure fabricated with the potassium hydroxide (KOH) anisotropically etched (100) silicon substrate has been deposited with a copper film as the bottom electrode of the programmable metallization cell (PMC) memory to significantly improve the resistive switching characteristic. As compared with the conventional flat copper electrode, this pyramid-structured electrode exhibited the set/reset voltage as low as 1/0.6 V and superior endurance of 2400 cycles at the set/reset voltages of -5/+3 V for the voltages pulsewidth of 1 mu s. The high performance of this PMC could be attributed to high local electrical fields at the tips of the pyramid structure, resulting in the formation of the narrower conductive filaments that facilitate the lower operation voltage and better endurance.
Sensitivity Enhancement of Ultraviolet Photodetectors With the Structure of p-NiO/Insulator-SiO2/n-ZnO Nanowires
(2015-08-01)
Li, Yu-Ren
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Wan, Chung-Yun
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Chang, Chia-Tsung
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Huang, Yu-Chih
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Tsai, Wan-Lin
A high-performance photodetector with the structure of NiO/SiO2/ZnO nanowires has been proposed. The devices with 6-nm-thick SiO2 exhibited a better rectification ratio (J(forward)/J(reverse)) of 246 at +/- 2 V, lower dark current density (J(dark)) of 3.5 x 10(-7) A/cm(2) at a reverse bias of 2 V, and superior ultraviolet (UV) sensitivity (I-UV/I-dark) of 16.23 than those without the SiO2 layer (J(forward)/J(reverse) = 44, Jdark = 4.7x10(-6) A/cm(2), and I-UV/I-dark = 5.5). The improved performance was mainly due to the ultrathin inserted SiO2 layer that builds a barrier height to minimize the transmission probability of low-energy carriers, leading to the enhancement of the UV sensing characteristics.
Thickness effect of NiO on the performance of ultraviolet sensors with p-NiO/n-ZnO nanowire heterojunction structure
(2015-08-01)
Li, Yu-Ren
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Wan, Chung-Yun
;
Chang, Chia-Tsung
;
Tsai, Wan-Lin
;
Huang, Yu-Chih
Based on the p-NiO/n-ZnO nanowire (NW) heterojunction structure, a high-performance ultraviolet (UV) sensor has been achieved in this work. The sputtered p-type NiO exhibited good coverage on the hydrothermally-grown n-type ZnO Nano-Wires (NW\'s). The devices with 250-nm-thick NiO obtained the highest UV light sensitivity (I-UV/I-Dark = 4.98; I-Visible/I-Dark = 3.82 biased at -2 V) under UV (lambda = 365 nm) intensity as low as 300 mu W/cm(2). Such p-n junction with thinner or thicker NiO layer led to worse UV detecting characteristics due to the fully-depleted NiO layer and larger series resistance, respectively. Furthermore, the N-2 annealing process can increase the UV light response and suppress the visible light response because of the reduced structural defects in ZnO NWs and the fewer interfacial defects (I-UV/I-Dark = 5.65; I-Visible/I-Dark = 1.35 biased at -2 V). (c) 2015 Elsevier Ltd. All rights reserved.