Browsing by Author "Yu, Cheng-Chang"

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Effects of Doping Ratio and Thermal Annealing on Structural and Electrical Properties of Boron-Doped ZnO Thin Films by Spray Pyrolysis
(2013-06-01)
Yu, Cheng-Chang
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Hsu, Yu-Ting
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Lee, Shao-Yi
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Lan, Wen-How
;
Kuo, Hsin-Hui
Boron-doped zinc oxide (BZO) thin films have been fabricated by spray pyrolysis on a glass substrate. The morphology and electrical properties of the thin films were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed. It was found that [B]/[Zn] ratio altered both the microstructure and concentration of the BZO thin films. The film grain size was reduced by increasing the [B]/[Zn] ratio. The highest Hall mobility was 3.65 cm(2)V(-1)s(-1) for the undoped ZnO thin film, and the highest carrier concentration of 1.0 x 10(19) cm(-3) was achieved for the as-deposited BZO thin film with [B]/[Zn] = 1.5 at. %. Conductivity was determined at different measurement temperatures and shallow donors provided the dominate conduction mechanism for the as-deposited BZO thin films. After 600 degrees C annealing, shallow level reduction and donors with a high activation energy of 129 +/- 6 meV in the BZO thin films were characterized, and the shallow donors that dominate the carrier concentration for the as-deposited spray-pyrolized BZO thin film were eliminated. (C) 2013 The Japan Society of Applied Physics
Effects of UV illumination on oxygen detection for ZnO film prepared by thermally oxidized Zn on sapphire substrate
(2014)
Yu, Cheng-Chang
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Hsu, Yu-Ting
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Lan, Wen-How
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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,
Improved Output Power of Nitride-Based Light-Emitting Diodes With Convex-Patterned Sapphire Substrates
(2012-10-01)
Hsu, Yu-Ting
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Yu, Cheng-Chang
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Huang, Kai-Feng
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Lan, Wen-How
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Huang, Jing-En
Nitride-based light-emitting diodes (LEDs) grown on different convex-patterned sapphire substrates are proposed and fabricated. The electrical and optical properties of these LEDs are discussed in detail. It is found that the LED with a ball-shape patterned sapphire substrate has the best crystalline quality and I-V characteristic. On the other hand, on reducing total internal reflection, the LED with hexagonal-shape patterned sapphire substrate (HPSS) has the best performance on output power and external quantum efficiency. In comparison to the LED without patterned substrate, the LED with HPSS has 175% and 165% enhancement on output power and external quantum efficiency, respectively.
Indium-Nitrogen Codoped Zinc Oxide Thin Film Deposited by Ultrasonic Spray Pyrolysis on n-(111) Si Substrate: The Effect of Film Thickness
(2014)
Yu, Cheng-Chang
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Lan, Wen-How
;
Huang, Kai-Feng
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電子物理學系
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Department of Electrophysics
Indium-nitrogen codoped zinc oxide (INZO) thin films were fabricated by spray pyrolysis deposition technique on n-(111) Si substrate with different film thicknesses at 450 degrees C using a precursor containing zinc acetate, ammonium acetate, and indium nitrate with 1 : 3 : 0.05 at.% concentration. The morphology and structure studies were carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The grain size of the films increased when increasing the film thickness. From XRD spectra, polycrystalline ZnO structure can be observed and the preferred orientation behavior varied from(002) to (101) as the film thickness increased. The concentration and mobility were investigated by Hall effect measurement. the p-type films with a hole mobility around 3 cm(2)V(-1)s(-1) and hole concentration around 3 x 10(19) cm(-3) can be achieved with film thickness less than 385 nm. The n-type conduction with concentration 1 x 10(20) cm(-3) is observed for film with thickness 1089 nm. The defect states were characterized by photoluminescence. With temperature-dependent conductivity analysis, acceptor state with activation energy 0.139 eV dominate the p type conduction for thin INZO film. And the Zn-related shallow donors with activation energy 0.029 eV dominate the n-type conduction for the thick INZO film.
UV Enhanced Oxygen Response Resistance Ratio of ZnO Prepared by Thermally Oxidized Zn on Sapphire Substrate
(2013)
Yu, Cheng-Chang
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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.