Sheng-Yuan Chu
National Cheng Kung University
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Featured researches published by Sheng-Yuan Chu.
Materials Letters | 2002
Walter Water; Sheng-Yuan Chu
Abstract In this paper, poly-crystal zinc oxide (ZnO) films with c -axis (002) orientation have been successfully grown on the silicon substrate by r.f. magnetron sputtering technique. The deposited films were characterized as a function of deposition temperature, argon–oxygen gas flow ratio, and r.f. power. Crystalline structures, stress and roughness characteristics of the films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurement. By controlling deposition parameters and annealing temperature, we could improve intrinsic stress and surface roughness of ZnO film. Preferred deposition condition was found to show good film quality for SAW device applications.
Journal of The Electrochemical Society | 2011
Ying-Chien Fang; Sheng-Yuan Chu; Po-Ching Kao; You-Ming Chuang; Zong-Liang Zeng
CaLa 2 (MoO 4 ) 4 :Sm 3+ , Eu 3+ phosphors are prepared using a convenient solid-state reaction route. The red emission intensity of Eu 3+ is enhanced by Sm 3+ ion codoping. The energy transfer mechanism from Sm 3+ to Eu 3+ was found to be a dipole-quadrupole interaction with a critical distance of 10.42 A. With increasing Eu 3+ doping content, the energy transfer efficiency (Sm 3+ → Eu 3+ ) gradually increased to 75.5%. The thermal quenching behavior was investigated using absorption and emission spectra. The thermal quenching temperature (T 50 ) of CaLa 2 (MoO 4 ) 4 :Sm 3+ ,Eu 3+ phosphors is above 200°C, and the activation energy of the thermal quenching process is 0.13 eV. The effect of codoped Sm 3+ ions on the thermal stability of CaLa 2 (MoO 4 ) 4 :Sm 3+ ,Eu 3+ phosphors is investigated.
Ceramics International | 2000
Sheng-Yuan Chu; Tser-Min Yan; Shen-Li Chen
Abstract A new sol–gel processing method to prepare ZnO-based varistor powders, using inexpensive zinc acetate dihydrate, ethylene glycol, n -propyl alcohol and glycerol as starting materials, is presented. Compared to conventional oxide-mixing techniques, this method yields powders with a more homogeneous distribution of dopants; the sintering temperature could be lowered by about 200 K to 1000°C and the grain size is much smaller which proves very helpful for achieving high breakdown strength. Microstructure and electrical characteristics of the sintered powders were investigated.
Materials Letters | 2002
Walter Water; Sheng-Yuan Chu; Yung-Der Juang; Shih-Jeh Wu
Abstract It is necessary for zinc oxide film to have high resistivity for piezoelectric applications. The ZnO films have been deposited by RF sputtering deposition system using Li-doped ZnO ceramics as the target and high oxygen ratio (100% oxygen) for high film resistivity. The maximum resistivity of ZnO film measured was 10 8 Ω cm in our experiments, and stronger intensity of c -axis orientation was grown at 50% oxygen ratio. Postdeposition annealing ZnO films in vacuum circumstance were found to relieve stress, avoid the electrode oxidation and increase resistivity one order. The preferred deposition conditions and annealing condition were obtained for piezoelectric application. Then, an over-mode resonator was made and showed a large return loss of 42 dB at the center frequency of about 2 GHz after annealing for 1 h in vacuum circumstance at 400 °C.
Applied Physics Letters | 2010
Zong-Liang Tseng; Po-Ching Kao; Meng-Fu Shih; Hsin-Hsuan Huang; Jing-Yuan Wang; Sheng-Yuan Chu
A hybrid resistance switching device consisting of ZnO nanorods embedded in an insulating polymethylmethacrylate (PMMA) heterostructure sandwiched between a transparent conductive film and an Al electrode is proposed. The current-voltage characteristics of the device are discussed in terms of the formation and rupture of its conductive filaments. The hybrid device shows stable electrical bistable behaviors after more than 200 resistance-switching cycles. The hybrid ZnO nanorod/PMMA device presented in this work has potential applications in the field of bistable random access memory devices.
Ferroelectrics | 2003
Sheng-Yuan Chu; Walter Water; Yung-Der Juang; Jih-Tsang Liaw
In this paper, samples of (Na x K 1 m x )NbO 3 where x = 0.1 m 1 and Li y (Na 0.5 K 0.5 ) 1 m y NbO 3 where y = 0.01 m 0.05 have been prepared by conventional ceramic technique. The prepared Sodium Potassium Niobate (Na x K 1 m x NbO 3 ) and Lithium Sodium Potassium Niobate (Li y (Na 0.5 K 0.5 ) 1 m y NbO 3 ) samples are characterized using X-ray diffraction method and grain size have been calculated using SEM photographs; the phase transitions have been observed from DSC experiments. Finally, the piezoelectric and dielectric characteristics of these ceramic systems are also investigated. Lithium dopants in (Na, K)NbO 3 ceramics play an important role on the ferroelectric curie temperature, dielectric constant, grain size as well as the planar mechanical coupling coefficient ( k p ) value.
Ferroelectrics | 2003
Sheng-Yuan Chu; Walter Water; Yung-Der Juang; Jih-Tsang Liaw; S. B. Dai
In this paper, xLi2O-yK2O-(1-x-y)Nb2O5, x = 0 − 1 and y = 0 − 1, system was partially studied using Lithium and Potassium Niobate as sintering materials in order to reduce the sintering temperature. The prepared lithium potassium niobate ceramics are characterized using X-ray diffraction method and grain size have been calculated using SEM photographs; the phase transitions have been observed from DSC experiment. Finally, the piezoelectric and dielectric characteristics of these mixed ceramic systems are also investigated. The planar mode electromechanical coupling coefficient kp reaches 33.5% and two phase transitions (orthorhombic—tetragonal; tetragonal—cubic) have been observed.
Applied Physics Letters | 2013
Bo-Yuan Su; Sheng-Yuan Chu; Yung-Der Juang; Han-Chang Chen
Ultraviolet (UV)-ozone photo-annealing was applied to fabricate low-temperature high-performance solution-processed thin-film transistors (TFTs). With UV-ozone treatment at the optimal temperature of 300 °C, TFT devices showed an improved field-effect mobility of 1.73 cm2 V−1 s−1, a subthreshold slope (S) of 0.32 V dec−1, an on/off-current ratio greater than 1.3 × 107, and good operational bias-stress stability compared to those of InGaZnO TFT devices fabricated with only a conventional thermal-annealing process. The results of X-ray photoelectron spectroscopy and the maximum density of the surface states (Ns) confirm that the device improvement originates from reduced oxygen-related defects and improved electron trapping due to UV-ozone irradiation.
Ultrasonics | 2003
Sheng-Yuan Chu; Walter Water; Jih-Tsang Liaw
Love mode acoustic devices are very promising as biosensors in liquid environments because of their high sensitivity. An experimental study of Love mode sensors based on ZnO/90 degrees rotated ST-cut quartz structure with different sputtering conditions to deposit ZnO films is presented. In order to achieve sensor with higher sensitivity, the effects of sputtering substrate temperatures to deposit ZnO films on the sensitivity of viscosity and conductivity were investigated. Phase velocity, sensitivity and temperature coefficient of frequency (TCF) of Love wave devices have been studied. The Love wave sensor has higher sensitivity as sputtering ZnO films on the unheated substrate than that of on the heated substrate. The maximum sensitivity up to -18.77 x 10(-8) m(2) s kg(-1) of ZnO film with thickness of 1.8 microm for a wavelength of 40 microm is much bigger than SiO(2)/quartz structure. In this research, we report ZnO/90 degrees rotated ST-cut quartz structure of Love wave sensors with high sensitivity of viscosity and conductivity in liquid circumstance and TCF of quartz is compensated by ZnO film.
CrystEngComm | 2015
Jian-Fu Tang; Hsiu-Hsien Su; Yang-Ming Lu; Sheng-Yuan Chu
This study developed a hydrothermal method for the growth of three types of zinc oxide (ZnO) nanostructures: nanorods, nanowalls and nanoflowers. The structures are produced at high densities with a high degree of uniformity on Al-coated SiO2 substrates without the need for surfactant. Unlike the random distribution of ZnO nanoflowers reported in previous studies, the proposed method makes it possible to control the distribution of these structures along the grooves created by altering the growth rate of ZnO nanorods and nanowalls. The number of ZnO nanoflowers created in this manner depends on the concentration of solution (HMT: hexamethylenetetramine) and reaction time. Measurements of cathodoluminescence (CL), X-ray diffractometry (XRD), and SEM-EDS confirm that the resulting structures are pure ZnO with good crystallinity. We also investigated the optical properties of these ZnO nanostructures and propose a possible growth mechanism.