Browsing by Author "Huang, Chien-Jung"

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Effects of UV illumination on oxygen detection for ZnO film prepared by thermally oxidized Zn on sapphire substrate
(2014)
Yu, Cheng-Chang
;
Hsu, Yu-Ting
;
Lan, Wen-How
;
Shih, Ming-Chang
;
Hong, Jin-Hua
The ZnO thin film prepared after the 600 degrees C oxidation of thermally-evaporated Zn thin film on sapphire substrate was studied. A nano structured surface morphology was observed by scanning electron microscope. With following Ti/Au metallization, the metal-semiconductor-metal (MSM) device was formed. With ultra violate (UV) light illumination come from the mercury lamp with a short pass filter, the device resistance variation under oxygen atmosphere was investigated. The reduction of detection response time and recovery time for this device with UV light illumination were observed also. After discussion based on the grain boundary connected model, the observed resistance variation controlled by the nano texture was realized. The UV light illumination technology shows an effective method to enhance the gas detection response time for this ZnO MSM gas sensor. Keywords: ZnO, MSM,
Enhanced photocatalytic decomposition of methylene blue by the heterostructure of PdO nanoflakes and TiO2 nanoparticles
(2012-12-15)
Huang, Chien-Jung
;
Pan, Fu-Ming
;
Chang, I-Chun
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材料科學與工程學系
;
Department of Materials Science and Engineering
We prepared PdO nanoflakes by reactive sputter deposition to form a heterostructure with TiO2 nanoparticles on the SiO2 substrate for the study of photocatalytic decomposition of methylene blue (MB) molecules. Although the PdO nanoflake has little photocatalytic activity toward MB decomposition, the PdO/TiO2 heterostructure has a photocatalytic activity toward MB decomposition under UV light illumination as large as twice that of bare TiO2 nanoparticles. The enhancement in the photocatalytic activity is ascribed to the fast photogenerated carrier separation resulting from the potential barrier formed at the heterojunction between the two oxide semiconductors. Although PdO nanoflakes can be photoexcited under visible light illumination, the PdO/TiO2 heterostructure exhibits little photocatalytic activity toward the MB decomposition. (C) 2012 Elsevier B. V. All rights reserved.
Fabrication of Porous Ti Structures with Nanostructures from Ti Powders by Femtosecond Laser Pulses
(2015-12-01)
Cheng, Chung-Wei
;
Huang, Chien-Jung
;
Cheng, Hui-Ta
;
Kuo, Ching-Nan
;
機械工程學系
The fabrication of titanium (Ti) porous structures covered with periodic nanostructures from micro Ti powders by femtosecond laser-induced sintering and simultaneous laser-induced periodic surface structures (LIPSS) are demonstrated. Different types of structures are obtained only by controlling the laser power of a femtosecond laser at wavelength 800 nm: sintered structures and sintered/melted structures with periodic nanostructures of period 550 similar to 650 nm.
Growth and Field Emission of Reactive Sputtered Pd-PdO Core-Shell Nanoflakes on Platinum
(2009)
Huang, Chien-Jung
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Pan, Fu-Ming
;
Tzeng, Tai-Cheng
;
Li-Chang
;
Sheu, Jeng-Tzong
Palladium oxide (PdO) was deposited on platinum by reactive sputter deposition, and the PdO thin film grown on the Pt substrate had a flakelike morphology. The nanosized flake had a core-shell structure with a single Pd grain encapsulated by a crystalline PdO surface layer. The formation of the PdO capped nanoflakes was ascribed to a large interfacial stress due to a lattice mismatch between PdO and Pt. Field emission characteristics of the nanoflakes were studied and a field-enhancement factor of 791 was obtained.
Growth and photoresponse study of PdO nanoflakes reactive-sputter deposited on SiO(2)
(2010-09-01)
Huang, Chien-Jung
;
Pan, Fu-Ming
;
Chen, Hsiu-Ying
;
Li-Chang
;
材料科學與工程學系
This study prepares PdO nanostructures on a SiO(2) substrate by reactive-sputter deposition and examines photoresponse characteristics of the thin films. PdO thin films deposited at 25 degrees C is composed of bowed nanoflakes standing on the SiO(2) substrate, which have a single-crystalline structure after thermal anneal at 400 degrees C. The 400 degrees C-annealed nanoflake thin film has a band gap energy in the red-light range (similar to 2.06 eV), and exhibits a very sensitive photoresponse upon the UV (365 nm) illumination. The high photoresponse sensitivity of the 400 degrees C-annealed nanoflake thin film is ascribed to a lower density of recombination centers and traps due to an excellent crystallinity and a high carrier extraction efficiency due to a low electrical resistivity. A slight decrease in the photocurrent density during the initial stage of the UV illumination is attributed to adsorption of O(2)(-) anions on the 400 degrees C-annealed nanoflakes. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3476567]
Growth and photoresponse study of PdO nanoflakes reactive-sputter deposited on SiO2
(2010-09-01)
Huang, Chien-Jung
;
Pan, Fu-Ming
;
Chen, Hsiu-Ying
;
Li-Chang
;
材料科學與工程學系
This study prepares PdO nanostructures on a SiO2 substrate by reactive-sputter deposition and examines photoresponse characteristics of the thin films. PdO thin films deposited at 25 degrees C is composed of bowed nanoflakes standing on the SiO2 substrate, which have a single-crystalline structure after thermal anneal at 400 degrees C. The 400 degrees C-annealed nanoflake thin film has a band gap energy in the red-light range (similar to 2.06 eV), and exhibits a very sensitive photoresponse upon the UV (365 nm) illumination. The high photoresponse sensitivity of the 400 degrees C-annealed nanoflake thin film is ascribed to a lower density of recombination centers and traps due to an excellent crystallinity and a high carrier extraction efficiency due to a low electrical resistivity. A slight decrease in the photocurrent density during the initial stage of the UV illumination is attributed to adsorption of O-2(-) anions on the 400 degrees C-annealed nanoflakes. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3476567]
Improved Characterization of High-Impedance Surfaces for Better Designs of Low Profile Antennas
(2012)
Huang, Chien-Jung
;
Kehn, Malcolm Ng Mou
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傳播研究所
;
Institute of Communication Studies
Low profile antenna designs using high impedance or artificial magnetic conducting ground planes composed of periodic structures have been receiving considerable research attention, but most if not all of them only use the reflection-phase of the normal incident plane wave to determine the high impedance frequency of operation. Considering the fact that the overlying antenna does not radiate toward only the normal direction, it is necessary to use numerous incident waves of different incident angles and polarizations to properly characterize the periodic structures for subsequently more appropriate antenna designs. Though in this paper the concept is built on planar corrugated surfaces [1], it can be extended to other periodic structures.
On the Nitrogen Doping in Erbium and Nitrogen Codoped Magnesium Zinc Oxide Diode by Spray Pyrolysis
(2020-01-01)
Chen, Chun-An
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Hsu, Yu-Ting
;
Lan, Wen-How
;
Huang, Kai-Feng
;
Chang, Kuo-Jen
Diodes with an erbium and nitrogen codoped magnesium zinc oxide (MgZnO:Er,N) active layer were fabricated by spray pyrolysis on Si substrate with aqueous solutions including magnesium nitrate, zinc acetate, erbium acetate, ammonium acetate, and indium nitrate precursors. Diodes with different nitrogen content in their precursor were prepared and their properties were investigated. With scanning electron microscopy, film surface with mixed hexagonal flakes and tiny blocks was characterized for all samples. Certain morphologies varied for samples with different N contents. In the photoluminescence analyses, the intensity of the oxygen-related defects peak increased with the increasing of nitrogen content. The diodes were fabricated with an Au and In deposition on the top and backside. The diode current-voltage as well as capacitance-voltage characteristics were examined. An ununiformed n-type concentration distribution with high concentration near the interface in the MgZnO:Er,N layer was characterized for all samples. Diodes with high nitrogen content exhibit reduced breakdown voltage and higher interface concentration characteristics. Under reversed bias conditions with an injection current of 50 mA, a light spectrum with two distinct green emissions around wavelengths 532 and 553 nm was observed. A small spectrum variation was characterized for diodes prepared from different nitrogen content. The diode luminescence characteristics were examined and the diode prepared from N/Zn=1 in the precursor showed an optimal injection current-to-luminescence property. The current and luminescence properties of the diode were characterized and discussed.
Photocatalytic study of Zinc Oxide with bismuth doping prepared by spray pyrolysis
(2015-09-01)
Lin, Tzu-Yang
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Hsu, Yu -Ting
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Lan, Wen-How
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Huang, Chien-Jung
;
Chen, Lung-Chien
The unintentionally doped and bismuth (Bi) doped zinc oxide (ZnO) films were prepared by spray pyrolysis at 450 degrees C with zinc acetate and bismuth nitrate precursor. The n-type conduction with concentration 6.13 x10(16)cm(-3) can be observed for the unintentionally doped ZnO. With the increasing of bismuth nitrate concentration in precursor, the p-type conduction can be observed. The p-type concentration 4.44x10(17)cm(-3) can be achieved for the film with the Bi/Zn atomic ratio 5% in the precursor. The photoluminescence spectroscopy with HeCd laser light source was studied for films with different Bi doping. The photocatalytic activity for the unintentionally doped and Bi-doped ZnO films was studied through the photodegradation of Congo red under UV light illumination. The effects of different Bi contents on photocatalytic activity are studied and discussed. Results show that appropriate Bi doping in ZnO can increase photocatalytic activity.
Thickness Study of Er-Doped Magnesium Zinc Oxide Diode by Spray Pyrolysis
(2018-12-01)
Hsu, Yu-Ting
;
Lee, Che-Chi
;
Lan, Wen-How
;
Huang, Kai-Feng
;
Chang, Kuo-Jen
Erbium-doped magnesium zinc oxides were prepared through spray pyrolysis deposition at 450 degrees C with an aqueous solution containing magnesium nitrate, zinc acetate, erbium acetate, and indium nitrate precursors. Diodes with different erbium-doped magnesium zinc oxide thicknesses were fabricated. The effect of erbium-doped magnesium zinc oxide was investigated. The crystalline structure and surface morphology were analyzed using X-ray diffraction and scanning electron microscopy. The films exhibited a zinc oxide structure, with (002), (101), and (102) planes and tiny rods in a mixed hexagonal flakes surface morphology. With the photoluminescence analyses, defect states were identified. The diodes were fabricated via a metallization process in which the top contact was Au and the bottom contact was In. The current-voltage characteristics of these diodes were characterized. The structure resistance increased with the increase in erbium-doped magnesium zinc oxide thickness. With a reverse bias in excess of 8 V, the light spectrum, with two distinct green light emissions at wavelengths of 532 nm and 553 nm, was observed. The light intensity that resulted when using a different operation current of the diodes was investigated. The diode with an erbium-doped magnesium zinc oxide thickness of 230 nm shows high light intensity with an operational current of 80 mA. The emission spectrum with different injection currents for the diodes was characterized and the mechanism is discussed.
UV Enhanced Oxygen Response Resistance Ratio of ZnO Prepared by Thermally Oxidized Zn on Sapphire Substrate
(2013)
Yu, Cheng-Chang
;
Hsu, Yu-Ting
;
Lan, Wen-How
;
Shih, Ming-Chang
;
Hong, Jin-Hua
ZnO thin film was fabricated by thermally oxidized Zn at 600 degrees C for 1 h. A surface containing nanostructured dumbbell and lines was observed by scanning electron microscope (SEM). The ZnO resistor device was formed after the following Ti/Aumetallization. The device resistance was characterized at different oxygen pressure environment in the dark and under ultraviolet (UV) light illumination coming from the mercury lamp with a short pass filter. The resistance increases with the increase of oxygen pressure. The resistance decreases and response increases with the increase of light intensity. Models considering the barrier height variation caused by the adsorbed oxygen related species were used to explain these results. The UV light illumination technology shows an effective method to enhance the detection response for this ZnO resistor oxygen sensor.