Sinter-patterning of oxide dielectric and high critical transition temperature films by pulsed neodymium:YAG laser

Using metallo-organic precursors formulated based on metal carboxylates, various oxide dielectric films (ZrO\sb2, Y\sb2O\sb3 yttria stabilized zirconium (YSZ)), perovskite based oxide films (BaTiO\sb3, SrTiO\sb3, CaTiO\sb3, YBa\sb2Cu\sb3O\sb{\rm 7-x}), and Bi\sb4Ti\sb3O\sb{12} film were fabricated by spin coating onto single crystal substrates such as Si, ZrO\sb2 and MgO.Different microstructures and line patterns were generated by varying the laser pulse energy level and profile. Laser processing parameters, deposited film thickness and organic burn-off showed strong influence on the film densification behavior in terms of grain size development and pore elimination. With changes in input pulse energy and focusing conditions, the laser beam was also used to sinter line patterns in several deposited thin and thick films. Tighter pore size distribution was found with the focused condition.Basically, the optimal focusing conditions used for laser sintering of different patterns (such as areas, lines, or dots) was found to depend on the spacing between the adjacent sintered spots and on the pulse energy. With laser irradiation at energy densities higher than the threshold value, liquid phase recrystallization, caused by rapid quenching of the oxide films from high temperature was formed from increasing energy density or the laser beam dwell time. Densification of the thin films by laser beams of different wavelength (Nd:YAG and ArF excimer lasers) was found to give rise to similar results, indicating that laser sintering of the pyrolyzed carboxylate-derived films is primarily controlled by photothermal rather than by photochemical effects.The high T\sb{\rm c} films patterning by this technique were found to exhibit high T\sb{\rm c} properties comparable to other techniques. The results of magnetic SQUID measurement show the laser patterned YBa\sb2Cu\sb3O\sb{\rm 7-x} films on ZrO\sb2/Si substrates to exhibit T\sb{\rm c} above 80 K and $\Delta$T\sb{\rm c} \sim 3K. Dielectric properties of laser-sintered BaTiO\sb3 and Bi\sb4Ti\sb3O\sb{12} films were observed to be approximately the same as those of film specimens processed by rapid zone firing. This laser process has thus been shown to offer significant potential for thin film patterning, a technique which can be applied to both insulation and passivation uses in integrated circuit devices and packages. (Abstract shortened with permission of author.)U of I OnlyETDs are only available to UIUC Users without author permissio

Electrochemically Deposited MoS2 and MnS Multilayers on Nickel Substrates in Inverse Opal Structure as Supercapacitor Microelectrodes

High-dispersion polystyrene (PS) microspheres with monodispersity were successfully synthesized by the non-emulsification polymerization method, and three-dimensional (3D) photonic crystals of PS microspheres were fabricated by electrophoretic self-assembly (EPSA). The metal nickel inverse opal structure (IOS) photonic crystal, of which the structural thickness can be freely adjusted via electrochemical deposition (ECD), and subsequently, MnS/MoS2/Ni-IOS specimens were also prepared by ECD. Excellent specific capacitance values (1880 F/g) were obtained at a charge current density of 5 A/g. The samples in this experiment were tested for 2000 cycles of cycle life and still retained a reasonably good level of 76.6% of their initial capacitance value. In this study, the inverse opal structure photonic crystal substrate was used as the starting point, and then the microelectrode material for the MnS/MoS2/Ni-IOS supercapacitor was synthesized. Our findings show that the MnS/MoS2/Ni-IOS microelectrode makes a viable technical contribution to the design and fabrication of high-performance supercapacitors

Low Humidifying Proton Exchange Membrane Fuel Cells with Enhanced Power and Pt–C–h-SiO₂ Anodes Prepared by Electrophoretic Deposition

Hydrophilic anodes were prepared by electrophoretic deposition using a slurry containing hollow SiO₂ (h-SiO₂) nanospheres and commercial Pt–C nanocatalysts. Low humidifying membrane–electrolyte assemblies (MEAs) were then prepared, which were incorporated into single proton exchange membrane fuel cells (PEMFCs). The effect of humidity on the cell voltage and that of the h-SiO₂ mass fraction on the MEA power performance and resistance were examined. The MEA stability was evaluated. Adding h-SiO₂ nanospheres to the catalyst increased the Pt mass activity from 1997 to 2657 A/g_Pt at an operating voltage of 0.6 V at a 100% relative humidity (RH); it increased from 1557 to 2611 A/g_Pt at 0.6 V and 30% RH. The current density voltage (<i>i</i>–<i>V</i>) and electrochemical-impedance results showed that the addition of h-SiO₂ reduced both anode activation loss and ohmic polarization. In addition, the low humidifying MEAs exhibited the same <i>i</i>–<i>V</i> relationship over a wide humidity range. After long-term operation in the absence of moisture, the cell voltage of a standard MEA was found to reduce by 15.55% whereas that of our proposed single cell dropped by only 7.18%. The power density of our proposed MEA was enhanced by a factor of 1.5 relative to a regular MEA

Effects of Nanoscaled Tin-Doped Indium Oxide on Liquid Crystals against Electrostatic Discharge

In our studies, it was confirmed that the cause of image sticking on liquid crystal (LC) cells is based on attacks of electrostatic discharge (ESD), which can be greatly relieved by doping with a small amount of tin-doped indium oxide (ITO) nanoparticles. Our proposed remedy allows the residual time of image sticking to be significantly reduced by more than an order and may protect the LC displays against any adverse ESD conditions, thus enhancing the overall display quality and reliability. In this study, conventional voltage-transmittance (V-T) characterization, voltage holding ratio (VHR) measurement, and ESD testing were employed to investigate the properties of the ITO-doped LCs. Based on our low voltage measurement results, it is interesting to find that ITO nanoparticles do not evidently alter the intrinsic properties of the LC. Namely, ITO additive initiates an early breakdown of the doped LC samples exposed to high electric fields. A model is proposed in this paper to depict the possible role of ITO particles applied in LCs