Papers by Author: Chien Min Cheng

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Authors: Hung Chi Yang, Tsung Fu Chien, Chien Min Cheng, Kai Huang Chen
Abstract: An implantable antenna for the applications of biomedical telemetry has been widely studied in the modern medical science. The purpose of this study is to design and fabricate an implantable antenna which exhibits enhanced bandwidth (25%) and miniaturization for the use of implantation. In this letter, the microwave dielectric ceramic (MgTa1.5Nb0.5O6) substrate which possesses high dielectric constant (εr = 28) and high quality factor is used as the substrate of the implantable antenna, a CPW-fed monopole dual spiral structure is adopted as the antenna pattern and fabricated by the print-screening technique. The effects of shape, length, size, and thicknesses of the proposed antenna would be evaluated and investigated in this letter. In addition, the center frequency is required to conform to the band (402 ~ 405 MHz) provided by Medical Implant Communication Services (MICS). From the experimental results of the proposed antenna immersed in phantom fluid, the optimum antenna exhibits a miniaturized volume of 288 mm3, bandwidth of 134 MHz (33%), return loss 16.32 db at 404 MHz, the SAR of 142 W/Kg, and gain of 16 db, respectively.
Authors: Chien Min Cheng, Kai Huang Chen, Yuan Tai Hsieh, Fuh Cheng Jong, Shih Fang Chen
Abstract: Aluminum Oxide microwave dielectric ceramics exhibit good microwave dielectric characteristics and suitable be used in the microwave devices. In this letter, using screen-printing technique and Ag/Pd paste, a novel dual-mode 2.4 GHz microstrip bandpass filter with U-shaped defected ground structure is screen printed on the Aluminum Oxide (Al2O3, relative dielectric constant=9.8) microwave dielectric ceramic substrate. In addition, a pair of input/output microstrip lines are designed to be 50 Ω and coupled to a λ/4×λ/4 square loop resonator. And in the ground plane, a U-shaped defected ground structure is used toλ excite the degenerate modes, which can be considered as a perturbation element to control the odd-mode frequency and -3 dB bandwidth of the bandpass filter. Finally, the coupling effects between these degenerate modes are presented and detailed investigated.
Authors: Chien Min Cheng, Kai Huang Chen, Hung Chi Yang, Cheng Fu Yang, Wen Cheng Tzou, Ming Chang Kuan, Fuh Cheng Jong
Abstract: In order to improve the sintering density and dielectric properties of the lead-free K0.5Na0.5NbO3-based ceramics, by the use of solid-state reaction, part of the Nb atoms are substituted by the Ta atoms to form K0.5Na0.5Nb0.95Ta0.05O3 ceramics and the dielectric characteristics are detail investigated in this letter. It is found that the phases of K0.5Na0.5Nb0.95Ta0.05O3 ceramics are pure perovskite with typical orthorhombic symmetry, in addition, no other secondary phases could be certified. For pure K0.5Na0.5Nb0.95Ta0.05O3 ceramics, the shapes of the grains are quadrate and which would due to the increase of the porosity and can not be eliminated easily. Because of the phase stability of pure K0.5Na0.5Nb0.95Ta0.05O3 ceramics is limited to 1140 °C in this study, higher sintering temperature (over than 1140 °C) is not suitable for the fabrication of K0.5Na0.5Nb0.95Ta0.05O3 ceramics. Moreover, the Ta atoms in the K0.5Na0.5NbO3-based ceramics could be used to improve the dielectric properties effectively, and it also reveals lower Curie temperature and lower phase transition temperature than the pure K0.5Na0.5NbO3 ceramics. In this letter, for 1120°C-sintered K0.5Na0.5Nb0.95Ta0.05O3 ceramics, the optimum bulk density is 95.6 % of the theorical density, the Curie temperature is 380 °C, and the optimum relative dielectric constant is 6107 at 10 kHz.
Authors: Min Chang Kuan, Kai Huang Chen, Chien Min Cheng, Chun Cheng Lin, Shih Fang Chen
Abstract: The structure and electrical characteristics of the lead-free Lix(K0.5Na0.5)1-x(Nb0.8Ta0.2)O3 (x=0~0.05) piezoelectric ceramics for the conventional solid-state reaction method and the B-side pre-calcined method were achieved and compared. For the B-side pre-calcined method, the lead-free ceramic material exhibited the excellent electrical and piezoelectric properties. The relative dielectric constant (εr) and loss (tan δ) of the Lix(K0.5Na0.5)1-x(Nb0.8Ta0.2)O3 for x=0.03 using the B-side pre-calcined method were 1223 and 0.021, respectively. In addition, the electromechanical coupling factors (kp) and Curie temperature (Tc) was 48.5 % and 315°C. Finally, the electrical properties of the lead-free Lix(K0.5Na0.5)1-x(Nb0.8Ta0.2)O3(x=0~0.05) homogeneity ceramics improved by the B-side pre-calcined method were also investigated and discussed.
Authors: Chien Min Cheng, Shih Fang Chen, Jen Hwan Tsai, Kai Huang Chen, Hsiu Hsien Su
Abstract: Lead-free potassium sodium niobate ceramic thin films were synthesized using rf magnetron sputtering technology for MFIS structures. The optimal sputtering parameters of the as-deposited KNN thin films for depositing times of 1h were obtained. Regarding the measured physical properties, the micro-structure and thickness of as-deposited KNN thin films for different oxygen concentration were obtained and compared by XRD patterns and SEM images. The surface roughness of KNN thin film was also observed by AFM morphology. The average grain size and root mean square roughness were 250 and 7.04 nm, respectively. For KNN thin films in the MFIS structure, the capacitance and leakage current density were 280 pF and 10-8A/cm2, respectively. We investigated that the leakage current density and the memory window increased, the capacitance critically increased as the oxygen concentration increased from 0 to 40%. However, the excess oxygen concentration process was decreased the electrical and physical of as-deposited KNN thin film. The effect of oxygen concentration on the physical and electrical characteristics of KNN thin films was investigated and determined.
Authors: Fann Wei Yang, Kai Huang Chen, Chien Min Cheng
Abstract: We have investigated the structure and ferroelectric properties of the Bi3.25La0.75Ti3O12 (BLT) thin films on SiO2/Si substrate fabricated by sol-gel method. We used the BLT films were annealed at various temperatures of 600, 650, and 700°C for one hour by conventional furnace annealing (CTA). The temperature dependence of leakage currents densities of ferroelectric BLT thin films. The crystalline structure of the prepared BLT thin films was analyzed by X-ray diffraction (XRD). Field emission scanning electron microscopy (FESEM) was used to observe the film thickness and the surface morphology including grain size and porosity. The leakage current density and capacitance of thin film were measured by HP4156C.
Authors: Shih Fang Chen, Kai Huang Chen, Chien Min Cheng
Abstract: In this study, the effects of La and V doping on Bi4Ti3O12 (BLTV) ferroelectric thin films deposited on ITO/glass substrates using rf magnetron sputtering were produced and investigated. The effect of oxygen concentration and RF power on the physical and electrical characteristics of BLTV thin films was determined. The physical characteristics of BLTV thin films were obtained by the XRD pattern, SEM and AFM. The variations of crystallization, surface roughness and thickness of BLTV thin films were discussed. The electrical properties of BLTV thin films deposited under various parameters were measured by the HP4156C.
Authors: Kai Huang Chen, Chia Lin Wu, Jian Yang Lin, Chien Min Cheng
Abstract: To improve the electrical and physical properties of as-deposited BSTZ thin films, the oxygen plasma treatment process were used by a low temperature treatment. In this study, the BSTZ thin films were post-treated under 150°C and 25 mTorr in the inductively coupled plasma. After oxygen plasma process treatment, the capacitance of thin films increased from 150 to 300pF in C-V curves, and the passivation of oxygen vacancy and defect in leakage current density curves were found. The influence of oxygen plasma on the chemical bonding state and crystalline structure was investigated by using XPS and XRD measurement.
Authors: Ming Chang Kuan, Kai Huang Chen, Wen Cheng Tzou, Chien Min Cheng, Yi Jun Lin
Abstract: In this study, the electrical properties of as-deposited Sr0.4Ba0.6Nb2O6 (SBN) ferroelectric thin films on SiO2/Si(100) substrates were improved by low temperature supercritical carbon dioxide fluid (SCF) process treatment. The as-deposited SBN ferroelectric thin films were treated by SCF process which mixed with pure H2O and propyl alcohol. After SCF process treatment, the memory windows increased in C-V curves, and the passivation of oxygen vacancy and defect in leakage current density curves were obtained. In addition, the improvement properties of as-deposited SBN thin films after SCF process treatment were found by XPS, C-V, and J-E measurement. Finally, the mechanism concerning the dependence of electrical properties of the SBN ferroelectric thin films on the SCF process was discussed.
Authors: Fann Wei Yang, Chien Min Cheng, Kai Huang Chen
Abstract: In this experimental, solid state method is used to synthesize proportioned nano-ZnO and SiO2 powders into Zn2SiO4 phosphor, and to achieve better control on grain size and grain shape than traditional powder. La is used to replace Mn; and to achieve better control on grain size and grain shape than traditional powder. With different sintering conditions, With different sintering conditions, the effect of the luminescent intensity due to sintering temperature and the concentration of activator would be discussed by the X-Ray Diffraction, SEM and TEM were utilized in the characterization of phase purity and microstructure of phosphor particles. Photoluminescence (PL) spectroscopy was utilized to characterize the optical properties. This use of phosphor materials is the application of the main light source, display components. Therefore, our study zinc silicate as the main principle of doping Mn, La of the characteristics of, expects to find the best glow.
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