Density of States-Based DC $I$– $V$ Model of Amorphous Gallium–Indium–Zinc-Oxide Thin-Film Transistors

The density of states (DOS)-based DC I-V model of an amorphous gallium-indium-zinc oxide (a-GIZO) thin-film transistor (TFT) is proposed and demonstrated with self-consistent methodologies for extracting parameters. By combining the optical charge-pumping technique and the nonlinear relation between the surface potential (phiS) and gate voltage (V _GS), it is verified that the proposed DC model reproduces well both the measured V _GS-dependent mobility and the I _DS-V _GS characteristics. Finally, the extracted DOS parameters are N _TA = 4.4 times 10¹⁷ cm^-3 middot eV^-1, N _DA = 3 times 10¹⁵ cm^-3 middot eV^-1, kT _TA = 0.023 eV, kT _DGA = 1.5 eV, and EO = 1.8 eV, with the formulas of exponential tail states and Gaussian deep states.     

Effect of Glass Composition on the Dielectric Properties of a Liquid-Phase-Sintered MgO-Doped BaTiO3

A series of BaTiO₃–MgO–glass mixtures has been sintered via liquid-phase sintering in a reducing atmosphere at 1280°C by controlling MgO/CaO ratio in an aluminum borosilicate glass composition, and the subsequent microstructure, phase evolution, and dielectric properties have been investigated. The growth of BaTiO₃ grains was inhibited in all of the prepared specimens with the evidence of Mg incorporation to the BaTiO₃ lattice from the glass. The change in MgO/CaO ratio in the glass notably modified the dielectric properties: a high MgO/CaO ratio in the glass resulted in a decreased dielectric constant, a decreased phase transition temperature, a broadened temperature range of phase transition, a decreased temperature coefficient of capacitance, and increased electrical resistivity.     

Protein Adsorption Modes Determine Reversible Cell Attachment on Poly(N‐isopropyl acrylamide) Brushes

Protein adsorption and reversible cell attachment are investigated as a function of the grafting density of poly(N‐isopropyl acrylamide) (PNIPAM) brushes. Prior studies demonstrated that the thermally driven collapse of grafted PNIPAM above the lower critical solution temperature of 32 °C is not required for protein adsorption. Here, the dependence of reversible, protein‐mediated cell adhesion on the polymer chain density, above and below the lower critical solution temperature, is reported. Above 32 °C, protein adsorption on PNIPAM brushes grafted from a non‐adsorbing, oligo(ethylene oxide)‐coated surface exhibits a maximum with respect to the grafting density. Few cells attach to either dilute or densely grafted PNIPAM chains, independent of whether the polymer brush collapses above 32 °C. However, both cells and proteins adsorb reversibly at intermediate chain densities. This supports a model in which the proteins, which support reversible cell attachment, adsorb by penetrating the brushes at intermediate grafting densities, under poor solvent conditions. In this scenario, reversible protein adsorption to PNIPAM brushes is determined by the thermal modulation of relative protein‐segment attraction and osmotic repulsion.     

Unsaturated polyester resins based on recycled PET: Preparation and curing behavior

The oligomers obtained from the glycolysis of Poly(ethlene terephthalate) (PET) waste were reacted with maleic anhydride to form a series of unsaturated polyester resins. The obtained resin was used to study the curing reaction with styrene by differential scanning calorimetry. The heats of reaction for styrene and polyester vinyl groups were measured by extrapolating the experimental results. Various kinetic parameters have been obtained using Kissinger expressions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1052–1057, 2001     

Carbon nanotube field effect transistors with suspended graphene gates

Novel field effect transistors with suspended graphene gates are demonstrated. By incorporating mechanical motion of the gate electrode, it is possible to improve the switching characteristics compared to a static gate, as shown by a combination of experimental measurements and numerical simulations. The mechanical motion of the graphene gate is confirmed by using atomic force microscopy to directly measure the electrostatic deflection. The device geometry investigated here can also provide a sensitive measurement technique for detecting high-frequency motion of suspended membranes as required, e.g., for mass sensing.     

Ridge formation and removal via annealing in exfoliated graphene

It is well known that graphene is a very promising material due to its excellent physical, chemical, and thermal properties. Previously, ridges in graphene on a substrate were found in epitaxial graphene on a SiC substrate. It was found in this study that ridges can be made on a graphene layer via mechanical exfoliation on a sapphire substrate, and that ridges can be created or removed through heating and cooling. Due to the difference of the thermal-expansion coefficients of the substrate and graphene, it can be said that thermal cycling causes compressive strain, which is released by forming ridges. Annealing was carried out in a vacuum chamber within the pressure range of 10(-3)-10(-6) Torr and at 900-1100 degrees C. To analyze the shapes and mechanical properties of the ridges, Raman spectroscopy and AFM measurement were performed. It was found that the ridges can be extended by defect as a nucleation center, and the graphene layer can be folded along the preexisting ridge during heating and cooling.     

Synthesis and characteristics of tb-doped Y2SiO5 nanophosphors and luminescent layer for enhanced photovoltaic cell performance

Nanophosphors based on green emitting terbium doped yttrium silicates with the general formula Y2SiO5:Tb3+ with a size of 30-60 nm were synthesized by the hydrothermal method. The prepared nanophosphors were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy and fluorescence spectroscopy. It was found that the nanophosphors crystallize in an X1-type monoclinic structure (P2(1)/c) and absorb UV light from 220 to 300 nm which they then down-convert into visible-light (strong green emission at around 545 nm (5D4-->7F(J. As TiO2-based dye-sensitized solar cells exhibit their maximum incident photon to current efficiency at around 500-600 nm, the wavelength-modulation characteristics of the nanophosphors can be efficient for dye-sensitized solar cell systems. Therefore, the Y2SiO5:Tb3+ nanophosphors were introduced into a TiO2-based dye-sensitized solar cell and their effects on the performance of the solar cell were investigated.     

Nanometer-scale oxide thin film transistor with potential for high-density image sensor applications

The integration of electronically active oxide components onto silicon circuits represents an innovative approach to improving the functionality of novel devices. Like most semiconductor devices, complementary-metal-oxide-semiconductor image sensors (CISs) have physical limitations when progressively scaled down to extremely small dimensions. In this paper, we propose a novel hybrid CIS architecture that is based on the combination of nanometer-scale amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) and a conventional Si photo diode (PD). With this approach, we aim to overcome the loss of quantum efficiency and image quality due to the continuous miniaturization of PDs. Specifically, the a-IGZO TFT with 180 nm gate length is probed to exhibit remarkable performance including low 1/f noise and high output gain, despite fabrication temperatures as low as 200 °C. In particular, excellent device performance is achieved using a double-layer gate dielectric (Al?O?/SiO?) combined with a trapezoidal active region formed by a tailored etching process. A self-aligned top gate structure is adopted to ensure low parasitic capacitance. Lastly, three-dimensional (3D) process simulation tools are employed to optimize the four-pixel CIS structure. The results demonstrate how our stacked hybrid device could be the starting point for new device strategies in image sensor architectures. Furthermore, we expect the proposed approach to be applicable to a wide range of micro- and nanoelectronic devices and systems.     

Effect of ball size and powder loading on the milling efficiency of a laboratory-scale wet ball mill

Alumina powder was wet-milled by zirconia balls with varying diameter at varying rotation speed, and the resultant particle size of the milled powder was analyzed. At a given rotation speed, there exists an optimum ball size to yield minimum particle size of alumina. The optimum ball diameter decreases as the rotation speed increases. This result has been interpreted in light of the competition between the reduced kinetic energy of the smaller balls (a negative source for milling efficiency) and the increased number of contact points of the smaller balls (a positive source), which yields the optimum ball diameter at an intermediate size. As the rotation speed increases, kinetic energy of the balls increases, which, in turn, shifts the optimum ball size toward a smaller value. As the powder loading increases from 1 to 35 g at a given rotation speed and ball size, the milling efficiency decreases monotonically.