Papers by Author: Jian Ling Zhao

Abstract: ZnO films were deposited on Si (100) substrate by ultrasonic spray pyrolysis at atmosphere. The film grown at optimum conditions is well crystallized with uniform, smooth and dense microstructure. Photoluminescence measurement shows a strong near band edge UV emission at 379nm and an almost undetectable deep-level emission band centered at 502nm. The resistivity of ZnO film is reduced by an order after N-In codoping, which produces p-type conduction with high hole concentration and hall mobility.

Abstract: ZnO thin films were grown on single-crystal Si(100) substrate by pulsed laser deposition (PLD) technique. The crystal structure and electrical properties were investigated as a function of oxygen partial pressure. Results indicate that highly c-axis oriented ZnO films can be obtained at all oxygen pressure range. With the increase of oxygen pressure, the crystallinity is further enhanced and the film presents smooth, uniform and dense packed columnar microstructure. Hall measurement indicates the resistivity of ZnO films increases with oxygen pressure. ZnO film grown at optimum conditions is employed to fabricate the MSM structured UV detectors with Ti/Pt/Au interdigital electrode configuration by standard photolithography and lift-off technique. The I-V characteristic and photo response measurement indicate a good ohmic contact between the ZnO film and electrode, and significant photoresponsivity under ultraviolet illumination.

Abstract: Dispersing barium titanate (BT) in aqueous media has received special attention due to economic and environmental considerations. A new kind of dispersant named poly (acrylic acid-co-itaconic acid) has been synthesized in our study. By adjusting reactant ratio and reactant condition poly (acrylic acid-co-itaconic acid) with different average molecular (2000~10000) and different content of itaconic acid (10% ~ 30%) have been obtained. Dispersing effects of poly (acrylic acid-co-itaconic acid) have been studied through zeta potential, sediment experiments, rheological behavior. It can be concluded from our study poly (acrylic acid-co-itaconic acid) containing 20% itaconic acid with Mw between 3000 and 5000 show the best dispersing effect.

Abstract: (Ba,Sr)TiO3 films with thickness between 1 ~ 20 µm are fabricated by electrophoretic deposition using (Ba,Sr)TiO3 nanopowder synthesized by different methods including sol-gel, coprecipitation and conventional solid phase synthesis. Experiments show that conventional solid phase synthesis need higher crystallization temperature (>1000°C) and result in larger size of particle while in sol-gel and coprecipitation process (Ba,Sr)TiO3 crystallizes at lower temperature and results in smaller size of particle . Powders synthesized from various routes have different surface property. Deposition parameter must be adjusted accordingly to obtain dense and smooth (Ba,Sr)TiO3 film.

Abstract: The effect of rare earth oxides (Y2O3 and Dy2O3) on the microstructure and electrical properties of the X7R-type ceramics for base metal internal electrode multilayer ceramic capacitor (BME-MLCC) was investigated. As the amount of Y increased, the dielectric constants and the dielectric losses increased, while the temperature coefficient of capacitors (TCC) curve rotated in counterclockwise direction. On the contrary, the dielectric constants decreased with Dy, and the TCC curve remained the same. The grain growth can be inhibited by the Dy2O3, concluded from XRD analysis. The different influences on dielectric properties between Y2O3 and Dy2O3 were discussed by defect chemistry. Y3+ acted as acceptor, performing B-site substitution, while Dy3+ showed the amphoteric behavior. By optimizing appropriate qualities of Y2O3 and Dy2O3, the most-compatible composition for BME X7R ceramics can be obtained.

Abstract: Textured bismuth titanate ceramics were successfully produced by spark plasma sintering, using plate-like Bi4Ti3O12 particles prepared by a molten salt method. The microstructure and electric properties of the samples were investigated. The results show that the textured Bi4Ti3O12 ceramics electric property is anisotropic in different direction, and spark plasma sintering is an effective sintering technology to get textured dense Bi4Ti3O12 ceramics at a low temperature.