Papers by Author: Chien Min Cheng

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.

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.

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.

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.

Abstract: We have investigated the structure and ferroelectric properties of the Bi_3.25La_0.75Ti₃O₁₂ (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.

Abstract: BaTiO₃/ which has good dielectric properties, they were widely used in ceramic capacitors, thermistors, etc. In this study, BaTiO₃/ ceramics prepared by sol-gel powder, then mixed in the organic polymer polyether imide (PEI) and dispersant (surface active agents) and silane coupling agent (Silane Coupling Agent) of the composite material on flexible substrates, And analysis of its properties and electrical properties. Increase by a ceramic powder, to explore the impact of the substrate. In the physical analysis is used XRD, SEM to measure the intensity of crystalline phase and surface uniformity of the electrical measurement using HP4294 measuring dielectric constant and dielectric loss.

Abstract: The structure and electrical characteristics of the lead-free Li_x(K_0.5Na_0.5)_1-x(Nb_0.8Ta_0.2)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 (ε_r) and loss (tan δ) of the Li_x(K_0.5Na_0.5)_1-x(Nb_0.8Ta_0.2)O₃ for x=0.03 using the B-side pre-calcined method were 1223 and 0.021, respectively. In addition, the electromechanical coupling factors (k_p) and Curie temperature (T_c) was 48.5 % and 315°C. Finally, the electrical properties of the lead-free Li_x(K_0.5Na_0.5)_1-x(Nb_0.8Ta_0.2)O₃(x=0~0.05) homogeneity ceramics improved by the B-side pre-calcined method were also investigated and discussed.

Abstract: In this study, we investigated that of Al/ Ba(Zr_0.1Ti_0.9)O₃ (BZT)/Pt/Ti/SiO₂/Silicon metal-ferroelectric-metal-insulator-semiconductor (MFM) ferroelectric structures and found the memory effect and capacitance of annealed BZT films during the different annealing temperature. Additionally, the capacitance and leakage current density were about 4.3 nF and 1´10^-6A/cm², respectively. From C-V curves, the ferroelectric properties and charges accumulation of annealed BZT films were also found during the annealing temperature of 700°C.

Abstract: In this study, thin films of CaBi₄Ti₄O₁₅ with preferential crystal orientation were prepared by the chemical solution deposition (CSD) technique on a SiO₂/Si substrate. The films consisted of a crystalline phase of bismuth-layer-structured dielectric. The as-deposited CaBi₄Ti₄O₁₅ thin films were crystallized in a conventional furnace annealing (RTA) under the temperature of 700 to 800°C for 1min. Structural and morphological characterization of the CBT thin films were investigated by X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM). The impedance analyzer HP4294A and HP4156C semiconductor parameters analyzer were used to measurement capacitance voltage (C-V) characteristics and leakage current density of electric field (J-E) characteristics by metal-ferroelectric-insulator- semiconductor (MFIS) structure. By the experimental result the CBT thin film in electrical field 20V, annealing temperature in 750°C the CBT thin film leaks the electric current is 1.88x10^-7 A/cm² and the memory window is 1.2V. In addition, we found the strongest (119) peak of as-deposited thin films as the annealed temperature of 750°C

Abstract: In this study, the electrical properties of as-deposited Sr_0.4Ba_0.6Nb₂O₆ (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.