Materials Science Forum Vols. 663-665

Abstract: Chitosan, a biocompatible, biodegradable, nontoxic polymer, is prepared from chitin, which is the second most naturally occurring biopolymer after cellulose. Sorbyl chitosan and p-aminobenzoyl chitosan were synthesized working under high-intensity ultrasound and their antimicrobial properties were analyzed against Escherichia coil, Staphylococcus aureus and Aspergillus niger. The structures of the derivatives were characterized by FTIR spectroscopy and elemental analysis. The results indicated that the products had the effect of bacteriostasis and the antibacterial activity increased with increasing the concentration. Acylated chitosan had better inhibiting effect on S. aureus than others. It was also found that the antifungal activities of the derivatives were stronger than that of chitosan.

Abstract: Chemical mechanical planarization (CMP) of copper interconnection in hydrogen peroxide (H2O2) as oxidizer based alkaline slurry was investigated. The new model is put forward, which is based on the characteristic of H2O2, chemical kinetics and mechanical removal. This properties of H2O2 can be effectively compensated the defect of surface topology during the process of polishing. Researcher previous study has shown that the surface is largely copper metal with Cu2O at low H2O2 concentrations and largely CuO at high H2O2 concentrations. Cu2O is more easily removed by both chemical and mechanical processes than CuO. During the CMP process, as the oxidizer concentration increases, the removal rate goes up initially followed by a gradual decay. This characteristic of oxidizer is used to achieve copper surface global planarity. The surface planarity was achieved by removing high area on the surface more quickly relative to the low area, because the concentration of Cu2O in the low area as the passivation film is more than the high area. Meanwhile the passivation film of the low area is thicker than the high area. In order to achieve polishing process optimization, the influence of pH adjustment and pressure, are also taken into consideration. Combining both RR and PE, the optimal H2O2 concentration and pressures are in range 1.0 ~1.5 vol% and 0.04 ~0.07 mpa, respectively. The roughness of surface which is measured by AFM is 0.49 after CMP.

Abstract: The paper reports on the PZT thick films preparation method by bonding bulk PZT on Si and then lapping PZT to suitable thicknesses. Epoxy resins with preferable thermostability were used as the intermediate adhesive layer in bonding process. A tight bonding of more than 10MPa was attained at suitable gradient bonding temperatures in an oven which were from 30 oC up to 105 oC according to 15 oC per thirty minutes and holding for more than 3h at 105 oC, and a pressure of more than 0.05MPa. Some properties of the prepared PZT thick films were tested. Finally, a piezoelectric MEMS power generator was fabricated by using the described techniques of PZT thick films preparation on silicon. The maximum output voltage under the resonant operation was measured.

Abstract: Highly ordered Ni and Ni-Cu nanowires were electrodeposited into the micropores of the porous anodic alumina (PAA) template which was fabricated by the method of two-step anodizing and the thickness of barrier layer which was formed during the anodizing process was rectified by applying current limited anodization steps. The X-ray diffration (XRD) was used to characterize the Ni and Ni-Cu nanowires and the morphology of these nanowires was examined by the way of scanning electron microscopy (SEM). The SQUID magnetometry was used to investigate the magetic properties of the nanowires. It is found that the coercivity and remanence ratio of Ni-Cu nanowire is larger than that of Ni nanowire.

Abstract: Magnetic iron oxide nanomaterials (e.g. Fe3O4 and γ-Fe2O3) with different morphologies have aroused extensive attention due to their fundamental research and potential technological applications such as magnetic recording media, magnetic fluids and magnetic drug-targeting. In this article Fe3O4 nanosheets were successfully synthesized using triblock copolymer (PEO)20(PPO)70(PEO)20 (P123) micelles as structure-directing agents in the presence of surfactant-assisted ethylene glycol (EG) and precipitator hexamethylenetetramine (HMTA) at 70 °C for 2 h in N2. The Fe3O4 nanosheets have irregular shape with thickness of the Fe3O4 nanosheets about 10-15 nm. The X-ray diffraction (XRD) pattern confirms the Fe3O4 nanosheets have magnetite structure and its nine distinguishable diffraction peaks can be perfectly indexed to the (111), (220), (311), (222), (400), (422), (511), (440), and (533) planes of the fcc structure of magnetite. Its saturation magnetization (σs) is 58.4 emu/g. The possible formation mechanism of the Fe3O4 nanosheets in present work is proposed.

Abstract: The Kondo insulator FeSi was prepared by DC magnetron sputtering and the effects of sputtering parameters on the formation of FeSi were investigated in detail. The formation of monosilicide FeSi was clarified using X-ray diffraction (XRD) and its microstructure was characterized by scanning electron microscopy (SEM). The results indicate that the sputtering gas pressure, the sputtering power and the Ar flux all have significantly effects on formation of FeSi and the crystalline of the film. The sputtering gas pressure has effects on sputtering yields, depositing rate and the energy of sputtering atoms, the sputtering power has effects on the kinetic energy and the diffusion ability of deposing atoms and the gas flux has the effects on the flowing state of Ar gas. The most optimal sputtering parameters for the preparation of the Kondo insulator FeSi by DC magnetron sputtering are given: 1.5 Pa for sputtering Ar pressure, 100 W for sputtering power and 20 SCCM for sputtering Ar flux.

Abstract: LiNbO3 (Mg:LN) crystal is an important electro-optical material and MgO-doped LiNbO3 was expected to improve its optical damage resistance. In the present work, we reported the Bridgman growth of MgO-doped LiNbO3 crystal. The growth parameters were discussed and the defects were investigated by the chemical etching method. The etch hillocks and etch pits were observed on the negative Z surface while only etch pits on the positive Z surface by the optical microscope and EPMA. The etching morphology was discussed considering the domain structure.

Abstract: In order to measure quantum yield (quantum efficiency) of light in the research of fluorescence excitation, rapid prototyping of micro-structure and photochemical, the absorption spectrum must be precisely measured. Therefore, the reflection on optical media interface, absorption and transmission in the medium must also be considered. In this article, we exhibit a set of reasonable experimental method which is designed to measure absorption spectrum by grating spectrometer. The results show that the obtained absorption lines are properly reliable if we select an appropriate way to settle the sample. Furthermore, it can be well generalized and applied to the selection of fluorescence excitation spectrum, photochemical reaction spectrum, photoelectric device spectrum.

Abstract: During the chemical synthesis nanometer-sized particles of ferrous iron oxide were in situ infiltrated into the mesopores in a porous silicon film. The microstructures of porous silicon and the magnetic properties of the nanometer-sized particles of the ferrous iron oxide were characterized with scanning electron microscopy, X-ray diffractometry, and the hysteresis loop measurement, respectively. Our results have demonstrated that the magnetic properties of the nanometer-sized Fe3O4 particles can be dramatically modified when they are confined into the mesopores of the porous silicon film.

Abstract: The solid solution crystal Pb(Zn1/3Nb2/3)O3-PbTiO3 [PZNT] has been grown from the high temperature solution. The crystallization behavior of PZNT was investigated. The evaporation of PbO was controlled by sealing crucible and the erosion of the melt or solution on Pt crucible was discussed. By optimizing growth conditions, high quality PZNT crystal was obtained. The ferroelectric properties were measured and the results showed as–grown crystal has high performance.