Controllable p-n junction formation in monolayer graphene using electrostatic substrate engineering

We investigate electric transport in graphene on SiO2 in the high field limit and report on the formation of p-n junctions. Previously, doping of graphene has been achieved by using multiple electrostatic gates, or charge transfer from adsorbants. Here we demonstrate a novel approach to create p-n junctions by changing the local electrostatic potential in the vicinity of one of the contacts without the use of extra gates. The approach is based on the electronic modification not of the graphene but of the substrate and produces a well-behaved, sharp junction whose position and height can be controlled.     

Modification of sputter deposited solid-state electrolyte thin films

All solid-state thin film batteries (TFBs) consisting of amorphous lithium phosphorus oxynitride (LiPON) solid electrolyte, crystalline LiMn₂O₄ cathode and crystalline SnO₂ anode have been fabricated and characterized. All of the thin films are prepared by RF magnetron sputtering. By fabricating under different pressures and applying low temperature post-annealing (200 °C), the performances of the LiPON electrolytes and SnO₂/LiPON/LiMn₂O₄ TFBs are improved. Suitable working pressures results in pinhole-free amorphous LiPON films with smooth surface and dense micro-structure. The TFBs post-annealed at 200 °C show smooth interface contacts between electrode and electrolyte thin films. The low pressure deposited and post-annealed TFBs exhibits lower impedance and higher cycling stability. Initial open-circuit voltage of 3.8 V and initial capacity of 12 μAh/cm² are obtained.     

Effects of mesoscopic poly(3,4-ethylenedioxythiophene) films as counter electrodes for dye-sensitized solar cells

Counter electrode coated with chemically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) in a dye-sensitized solar cell (DSSC) was studied. The surface morphology and the nature of I⁻/I₃⁻ redox reaction based on PEDOT film were investigated using Atomic Force Microscopy and Cyclic Voltammetry, respectively. The performance of the DSSCs containing the PEDOT coated electrode was compared with sputtered-Pt electrode. We found that the root mean square roughness decreases and conductivity increases as the molar ratio of imidazole (Im)/EDOT in the PEDOT film increases. The DSSC containing the PEDOT coated on fluorine doped tin oxide glass with Im/EDOT molar ratio of 2.0, showed a conversion efficiency of 7.44% compared to that with sputtered-Pt electrode (7.77%). The high photocurrents were attributed to the large effective surface area of the electrode material resulting in good catalytic properties for I₃⁻ reduction. Therefore, the incorporation of a multi-walled carbon nanotube (MWCNT) in the PEDOT film, coated on various substrates was also investigated. The DSSC containing the PEDOT films with 0.6 wt.% of MWCNT on stainless steel as counter electrode had the best cell performance of 8.08% with short-circuit current density, open-circuit voltage and fill factor of 17.00 mA cm⁻², 720 mV and 0.66, respectively.     

State Boundary Surfaces for an Aged Compacted Clay

The yielding and the peak strength of an aged compacted clay were studied by conducting a series of suction-controlled triaxial tests. The test results were interpreted using the framework of intrinsic properties of reconstituted soil. The peak strength envelopes of undisturbed samples lie above those of reconstituted samples. The suction provides additional attractive forces to stabilize the soil structure, which result in the augmentation of the yield stress and peak strength envelope. The shear strength is normalized by the equivalent preconsolidation pressure (pe′) and Hvorslev surfaces are identified from undisturbed samples which expand with suction. A single peak strength envelope and Hvorslev surface will be emerged from the saturated and unsaturated (degree of saturation >80%) samples if the shear strength data are presented in terms of the average skeleton stress. The influence of the soil structure on the shear strength of the aged compacted clay may be measured by the ratio of normalized strengths at the intrinsic critical state which is about 1.26     

Design and Analysis of Shock-Absorbing Structure for Flat Panel Display

In order to protect the fragile panel of a liquid crystal display (LCD) from damage caused by shock, a shock-absorbing structure designed to absorb most of the shock energy can be installed between the panel and the frame. The design methodology proposed in this paper uses the topology optimization technique in designing this shock-absorbing structure. The objective is to minimize the maximal panel stress with the shock-absorbing structure, which is designed to be of minimal weight. An algorithm which integrates three modules-the finite-element software ANSYS/LS-DYNA used as the structural analysis tool, the optimization module based on the differential evolution method, and a topology module - is developed to achieve crashworthiness design. Numerical results show that an optimal layout of the shock-absorbing structure with minimal weight is obtained. And, this shock-absorbing structure is proven to effectively increase LCD shock resistance.     

Electrical Characteristics of Passivated Pseudomorphic HEMTs With $hbox{P}_{hbox{2}}hbox{S}_{hbox{5}}/(hbox{NH}_{hbox{4}})_{hbox{2}}hbox{S}_{hbox{X}}$ Pretreatment

This paper elucidates the dc, pulse I-V, microwave, flicker noise, and power properties of AlGaAs/InGaAs pseudomorphic high electron mobility transistors (pHEMTs) after various ex situ sulfur pretreatments. The pHEMTs were pretreated with NH₄OH, (NH₄)₂S_X, and P₂S₅/(NH₄)₂S_X solutions before SiO₂ passivation to reduce the GaAs native oxide-related surface states. Stable phosphorus oxides and sulfur bound to the Ga and As species can be efficiently obtained using P₂S₅/(NH₄)₂S_X pretreatment; therefore, the leakage current in pHEMT was reduced following this process. Atomic force microscopy measurements indicated that the phosphorus oxides formed by P₂S₅/(NH₄)₂S_X treatment also provided a better surface roughness than obtained following traditional (NH₄)2S_X-only pretreatment, reducing mobility degradation after sulfur pretreatment. Based on the dc and 1 mus pulse I-V measurement results, P₂S₅/(NH₄)₂S_X-treated pHEMT exhibited very similar I_ds trends, especially at high currents; however, NH₄OH, (NH₄)₂S_X treatments clearly reduced the current upon pulse measurement because of the presence of surface traps. Hence, this novel pretreatment method has great potential for highly linear microwave power transistor applications.     

An improved single‐stage Flyback PFC converter for high‐luminance lighting LED lamps

This paper presents a high‐performance LED lamp driver with an improved single‐stage Flyback configuration. A constant current control method is used to regulate the lamp current and brightness. A laboratory prototype has been built and tested. With the prototype, high efficiency, high power factor, and constant lamp current can be achieved under different pieces of LED series connection. Copyright © 2007 John Wiley & Sons, Ltd.     

Cell-Penetrating Delivery of Nitric Oxide by Biocompatible Dinitrosyl Iron Complex and Its Dermato-Physiological Implications

After the discovery of endogenous dinitrosyl iron complexes (DNICs) as a potential biological equivalent of nitric oxide (NO), bioinorganic engineering of [Fe(NO)₂] unit has emerged to develop biomimetic DNICs [(NO)₂Fe(L)₂] as a chemical biology tool for controlled delivery of NO. For example, water-soluble DNIC [Fe₂(μ-SCH₂CH₂OH)₂(NO)₄] (DNIC-1) was explored for oral delivery of NO to the brain and for the activation of hippocampal neurogenesis. However, the kinetics and mechanism for cellular uptake and intracellular release of NO, as well as the biocompatibility of synthetic DNICs, remain elusive. Prompted by the potential application of NO to dermato-physiological regulations, in this study, cellular uptake and intracellular delivery of DNIC [Fe₂(μ-SCH₂CH₂COOH)₂(NO)₄] (DNIC-2) and its regulatory effect/biocompatibility toward epidermal cells were investigated. Upon the treatment of DNIC-2 to human fibroblast cells, cellular uptake of DNIC-2 followed by transformation into protein-bound DNICs occur to trigger the intracellular release of NO with a half-life of 1.8 ± 0.2 h. As opposed to the burst release of extracellular NO from diethylamine NONOate (DEANO), the cell-penetrating nature of DNIC-2 rationalizes its overwhelming efficacy for intracellular delivery of NO. Moreover, NO-delivery DNIC-2 can regulate cell proliferation, accelerate wound healing, and enhance the deposition of collagen in human fibroblast cells. Based on the in vitro and in vivo biocompatibility evaluation, biocompatible DNIC-2 holds the potential to be a novel active ingredient for skincare products.     

Motivated response styles: The role of cultural values, regulatory focus, and self-consciousness in socially desirable responding.

Three studies investigated the relations between cultural values and socially desirable responding, the processes that underlie them, and factors that influence the strength of the relations. Results indicated that individualism was associated with self-deceptive enhancement but not impression management, whereas collectivism was associated with impression management but not self-deceptive enhancement. Regulatory focus was found to mediate these relations. A promotion focus mediated the relation between individualism and self-deceptive enhancement, whereas a prevention focus mediated the relation between collectivism and impression management. This mediation pattern held regardless of whether individualism and collectivism were determined at the group level (Study 1) or measured at the individual level (Studies 2–3), whether socially desirable responding was operationalized as a scale measure (Studies 1–3) or as reactions to behavioral scenarios (Study 2), and across different measures of regulatory focus. This general mediation pattern was found to be moderated by type of self-consciousness (Study 3): The promotion focus mediation was stronger for participants low (vs. high) in private self-consciousness, and the prevention focus mediation was stronger for participants high (vs. low) in public self-consciousness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Study of the characteristics and corrosion behavior for the Zr-based metallic glass thin film fabricated by pulse magnetron sputtering process

Two sets of source target which consist of ZrCuAlNiV and ZrTiAlNiV, respectively were selected as the target materials for preparing a series of thin film coatings on the 304 stainless steel substrate by DC pulse magnetron sputtering process. The microstructures of these as-prepared ZrCuAlNiV and ZrTiAlNiV thin films were examined by X-ray diffraction and TEM observation. In parallel, the characteristic analysis of these ZrCuAlNiV and ZrTiAlNiV alloy thin films including surface roughness, and corrosion resistance were analyzed by atomic force microscopy (AFM), and tested by electrochemical method as well as salt spray testing, respectively. The results showed that the ZrCuAlNiV thin film exhibits a typical amorphous microstructure and smooth surface with average roughness about 1 nm. The ZrCuAlNiV thin film performs similar corrosion resistance to 304 stainless steel according to the result of salt spray testing in 5% NaCl solution. Additionally, the AC impedance value of ZrCuAlNiV is 20 times than 316L stainless steel and 4 times than ZrTiAlNiV, implying that the ZrCuAlNiV thin film has better corrosion resistance than the others owing to its amorphous state.