Progress in Functional Materials

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Authors: Sheng Zhao Wang, Ying Peng Yin, Chun Juan Nan, Ming Ji Shi
Abstract: By PECVD deposition technology, we mainly investigated the influence of substrate on intrinsic amorphous/microcrystalline silicon thin film prepared at 300°C. We study the crystallization ratio, grain size of the silicon thin film specially. The results reveal that the crystallization ratio and grain size of the silicon thin film changed along with different substrates. The silicon thin film crystallization ratio and grain size changed sharply when using glass and stainless steel substrate. On this work we think ideal μc-Si:H can be obtained by using glass as substrate and in the suitable experimental conditions.
169
Authors: Jing Zhang
Abstract: We present a fully coupled thermal-electrical-mechanical finite element based model to study material degradation behaviors of high-frequency electronic devices. The mechanisms of degradation and ultimately failure in wide bandgap (WBG) devices are very complex. Under operating conditions, the devices are usually subject to high electric fields, high stress/strain fields, high current densities, high temperatures and high thermal gradients. Moreover, these phenomena are coupled together. The presented finite element model is capable of computing stress, temperature, and electric fields based on an innovative finite element approach for the solution of non-linear coupled thermal-electrical-mechanical problems. The model can be applied to wide bandgap electronic devices to address major issues of performance and lifetime.
173
Authors: X.F. Chen, J. Li, T.T. Feng, Y.S. Jiang, X.H. Zhang, H.T. Wu, Y.L. Yue
Abstract: The pseudobrookite-structure MgTi2O5 was successfully synthesized by the aqueous sol-gel method using titanium dioxide and magnesium nitrate as starting materials instead of expensive organic solvent and metal alkoxides. The as-prepared nanopowders were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscope (TEM), respectively. The results showed that the calcinations process of gel consisted of a series of oxidation and combustion reactions, accompanied by significantly exothermal effects. Highly reactive nanosized magnesium titanate powders were successfully obtained at 650 °C with less than ~100 nm.
177
Authors: Xin De Tang, Ye Chen, Fa Qi Yu, Mei Shan Pei
Abstract: Organic/inorganic hybrid materials based upon stimuli-responsive copolymers have attracted an inceasing attention. Compared with the polymeric materials, these hybrid materials can form aggregates in aqueous solution with much more stable shape-persistance due to the inorganic structure, which facilitate the mass delivery and long-term life. A novel hybrid material based on a new reactive block copolymer, poly(ethylene oxide)-block-poly{3-(trimethoxysilyl)propyl methacrylate-co-N-isopropylacrylamide-co-6-[4-(4-methoxyphenylazo)phenoxy]hexyl methacrylate} [PEO-P(TMSPMA-NIPAM-AzoMA)] was synthesized via atom transfer radical polymerization (ATRP). The vesicles were obtained by self-assembly of the resulting block copolymer in a selective solvent, and then the PTMSPMA block was subjected to hydrolysis and polycondensation reaction to fix vesicle wall in the presence of triethylamine as a catalyst. The photo- and thermo- dual-responsive properties of the vesicles were investigated.
181
Authors: Qing Lan Ma, Rui Xiong, Yuan Ming Huang
Abstract: Metal-semiconductor Zn/ZnO core-shell structures are fabricated by a simple ultrasonic process of raw Zn particles in water. The crystal structure, morphologies and fluorescence of the Zn/ZnO core-shell particles are characterized with X-ray diffraction (XRD), scanning electronic microscopy (SEM) and fluorescence spectrophotometer. The XRD pattern confirms that the shells of the Zn/ZnO core-shell particles are composed of Wurtzite ZnO crystals. The SEM study clearly exhibits the formation of ZnO on the surface of Zn spheres. The room-temperature fluorescence spectra have been observed a strong ultraviolet (UV)-visible emission at 381 nm and a yellow-green deep-level emission at about 534 nm. It is noted that the very broad green emission at 510 nm appears in the ZnO crystals with increasing the content of ZnO shell on the surface of Zn spheres. Furthermore, a possible formed mechanism of ZnO shells on the Zn core is discussed.
185
Authors: An Hai Tseng, Yei Fai Chiang, Dong Po Wang
Abstract: Contactless electroreflectance(CER)spectra of Zn and O-polarity faces of a c-plane ZnO bulk were measured at room temperature. Besides a depletion electric field existing in the sample, it is known that there is a polarization electric field due to nonzero spontaneous polarization. In this work, a mercury lamp was focused on the ZnO sample in the CER measurements to provide a photo-biased voltage to reduce strength of electric field of the sample. It was found that the spectrum with Hg lamp being on is more blue-shifted and its amplitude is smaller than that without Hg lamp. Thus the type of transition was attributed to excitonic transition. The shift of the excitonic transition-energies of the Zn- and O-faces were obtained by fitting experimental CER spectra by using Lorenzian line-shapes. In addition, the polarity of faces can be determined by the amount of shift with Hg lamp being on.
189
Authors: X.F. Chen, J. Li, T.T. Feng, Y.S. Jiang, X.H. Zhang, H.T. Wu, Y.L. Yue
Abstract: The willemite-type Zn2SiO4 was successfully synthesized by the aqueous sol-gel method using Si sols dioxide and zinc nitrate as starting materials instead of expensive organic solvent and metal alkoxides. The as-prepared nanopowders were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscope (SEM), respectively. The results showed that the calcination process of gel consisted of a series of oxidation and combustion reactions, accompanied by significantly exothermal effects. Highly reactive nanosized Zn2SiO4 powders were successfully obtained at 800 °C with particle size ~100 nm. By comparison, the aqueous sol-gel process was the most effective and least expensive technique used for the preparation of Zn2SiO4 nanopowders.
193
Authors: Bao Gai Zhai, Yuan Ming Huang
Abstract: Polystyrene encapsulated phosphors SrAl2O4:Eu2+,Dy3+ were prepared by dispersing the phosphors into the matrix of polystyrene. The phase, morphology and optical properties of the polystyrene encapsulated phosphors were characterized with X-ray diffractometry, scanning electron microscopy and photoluminescence (PL) spectroscopy, respectively. It has been observed that both the PL spectrum and the luminescent color of the polystyrene encapsulated phosphors can be dramatically modified although the phosphorescence of the polystyrene encapsulated phosphors is not affected. Tunable photoluminescent colors from green to deep-blue are expected for the polystyrene encapsulated phosphors by the control of the weight percentage of the phosphors in the composites.
197
Authors: Shou Xiang Chen, Xiu Lun Yang, Xiang Feng Meng, Yu Rong Wang, Lin Hui Wang, Guo Yan Dong
Abstract: Plane-wave expansion method was employed to analyze the photonic band gap in two-dimensional silicon nitride photonic crystal. The effects of filling ratio and lattice structure type on the photonic band gap were studied. The results showed that two-dimensional dielectric cylinder type silicon nitride photonic crystal only has TE mode band gap, while, the air column type photonic crystal has complete band gap for TE and TM modes simultaneously. The distribution of band gap can be influenced by the filling ratio of dielectric materials and the lattice type. It is shown that the triangular lattice structure is much easier to form band gap than square lattice structure.
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Authors: Sheng Zhao Wang, Ying Peng Yin, Lan Li Chen, Chun Juan Nan
Abstract: ZrO2 sols were obtained by hydrothermal synthesis. With different hydrothermal synthesis time, ZrO2 particle size varied from 5nm to 16nm. And ZrO2 thin films were prepared with spin coating method. ZrO2 thin films were characterized or examined by many kinds of instruments. And 1-on-1 laser-induced damage threshold tests on ZrO2 films were carried out. Refractive index and thickness of the ZrO2-PVP films were measured by means of automatic scanning spectroscopic ellipsometer and the refractive index of ZrO2 -PVP film changed with the addition of PVP content.
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