Unraveling the Physics of Vertical Organic Field Effect Transistors through Nanoscale Engineering of a Self-Assembled Transparent Electrode

While organic transistors' performances are continually pushed to achieve lower power consumption, higher working frequencies, and higher current densities, a new type of organic transistors characterized by a vertical architecture offers a radically different design approach to outperform its traditional counterparts. Naturally, the distinct vertical architecture gives way to different governing physical ground rules and structural key features such as the need for an embedded transparent electrode. In this paper, we make use of a zero-frequency electric field-transparent patterned electrode produced through block-copolymer self-assembly based lithography to control the performances of the vertical organic field effect transistor (VOFET) and to study its governing physical mechanisms. Unlike other VOFET structures, this design, involving well-defined electrode architecture, is fully tractable, allowing for detailed modeling, analysis, and optimization. We provide for the first time a complete account of the physics underpinning the VOFET operation, considering two complementary mechanisms: the virtual contact formation (Schottky barrier lowering) and the induced potential barrier (solid-state triode-like shielding). We demonstrate how each mechanism, separately, accounts for the link between controllable nanoscale structural modifications in the patterned electrode and the VOFET performances. For example, the ON/OFF current ratio increases by up to 2 orders of magnitude when the perforations aspect ratio (height/width) decreases from ～0.2 to ～0.1. The patterned electrode is demonstrated to be not only penetrable to zero-frequency electric fields but also transparent in the visible spectrum, featuring uniformity, spike-free structure, material diversity, amenability with flexible surfaces, low sheet resistance (20-2000 Ω sq(-1)) and high transparency (60-90%). The excellent layer transparency of the patterned electrode and the VOFET's exceptional electrical performances make them both promising elements for future transparent and/or efficient organic electronics.     

Stable cycling of double-walled silicon nanotube battery anodes through solid-electrolyte interphase control

Although the performance of lithium ion-batteries continues to improve, their energy density and cycle life remain insufficient for applications in consumer electronics, transport and large-scale renewable energy storage. Silicon has a large charge storage capacity and this makes it an attractive anode material, but pulverization during cycling and an unstable solid-electrolyte interphase has limited the cycle life of silicon anodes to hundreds of cycles. Here, we show that anodes consisting of an active silicon nanotube surrounded by an ion-permeable silicon oxide shell can cycle over 6,000 times in half cells while retaining more than 85% of their initial capacity. The outer surface of the silicon nanotube is prevented from expansion by the oxide shell, and the expanding inner surface is not exposed to the electrolyte, resulting in a stable solid-electrolyte interphase. Batteries containing these double-walled silicon nanotube anodes exhibit charge capacities approximately eight times larger than conventional carbon anodes and charging rates of up to 20C (a rate of 1C corresponds to complete charge or discharge in one hour).     

Quantitative structured-illumination phase microscopy

We introduce a quantitative phase imaging method for homogeneous objects with a bright field transmission microscope by using an amplitude mask and a digital processing algorithm. A known amplitude pattern is imaged on the sample plane containing a thick phase object by placing an amplitude mask in the field diaphragm of the microscope. The phase object distorts the amplitude pattern according to its optical path length (OPL) profile, and the distorted pattern is recorded in a CCD detector. A digital processing algorithm then estimates the object's quantitative OPL profile based on a closed form analytical solution, which is derived using a ray optics model for objects with small OPL gradients.     

Optical encoder based on a nondiffractive beam

Optical encoders are used in industrial and laboratory motion equipment to measure rotations and linear displacements. We introduce a design of an optical encoder based on a nondiffractive beam. We expect that the invariant profile and radial symmetry of the nondiffractive beam provide the design with remarkable tolerance to mechanical perturbations. We experimentally demonstrate that the proposed design generates a suitable output sinusoidal signal with low harmonic distortion. Moreover, we present a numerical model of the system based on the angular spectrum approximation whose predictions are in excellent agreement with the experimental results.     

Use of UV-C treatments to maintain quality and extend the shelf life of green fresh-cut bell pepper (Capsicum annuum L.)

Abstract: The objective of this work was to select a Ultraviolet‐C (UV‐C) treatment for fresh‐cut mature green bell pepper, and to evaluate the effect of its combination with refrigeration on quality maintenance. Bell pepper sticks were treated with 0, 3, 10, or 20 kJ/m² UV‐C in the outer (O), inner (I), or both sides of the pericarp (I/O) and stored for 8 d at 10 °C. During the first 5 d of storage, all UV‐C treatments reduced deterioration as compared to the control. The treatment with 20 kJ/m² I/O was the most effective to reduce deterioration, and was used for further evaluations. In a second group of experiments, mature green bell pepper sticks were treated with 20 kJ/m² I/O, stored at 5 °C for 7 or 12 d and assessed for physical and chemical analysis, and microbiological quality. UV‐C‐treated fruit showed lower exudates and shriveling than the control. UV exposure also reduced decay, tissue damage, and electrolyte leakage. After 12 d at 5 °C, UV‐C irradiated peppers remained firmer and had higher resistance to deformation than the control. The UV‐C treatments also reduced weight loss and pectin solubilization. UV‐C exposure decreased the counts of mesophile bacteria and molds, and did not affect acidity or sugars. UV‐C‐treated fruit stored for 0 or 7 d at 5 °C did not show major differences in antioxidants from the control as measured against DPPH^? or ABTS^?+ radicals. Results suggest that UV‐C exposure is useful to maintain quality of refrigerated fresh‐cut green pepper. Practical Application: Exposure to UV‐C radiation before packing and refrigeration could be a useful nonchemical alternative to maintain quality and reduce postharvest losses in the fresh‐cut industry.     

Spatially resolved characteristics of pharmaceutical sprays

Spatially resolved drop size, velocity, and volume flux data for five different spray coating guns were described in this study. Such spatially resolved measurements show how sprays respond to changes in operating conditions and gun design in ways that less complete measurements can not provide. Data for instance, allow us to recognize the unique drop size distribution of one of the sprays tested, which ultimately was an important factor in determining the dual roles of the shaping air flows: depending on drop size, viscosity, and the magnitude of the shaping air velocity, the shaping air can either pinch or induce secondary atomization to the sprays. When the former outweighs the latter, a dumbbell‐shaped spray develops; a more uniform spray results when the opposite occurs. Volume flux data from the different sprays also suggest that a more robust and consistent tablet coating process can likely be designed by utilizing multiple overlapping round sprays. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Children's low affective perspective-taking ability is associated with low self-initiated pro-sociality.

Children's affective perspective-taking (APT) may provide a basis for efficient social interaction. The APT abilities of 83 children from 46 same-sex sibling pairs (ages 36 to 72 months, M = 52.8; SD = 12.6) were assessed through their reactions to affectively loaded story situations, and children whose APT ability (but not general cognitive abilities) was low relative to other children of their age were designated as Low-APT children. These children were not less pro-social when specific social cues or requests for pro-social behavior were given by experimenters. However, low APT may hinder children's ability to infer the need for pro-social action from relatively subtle social cues. Although 46.9% of nonlow APT children behaved pro-socially in at least two of three opportunities they were given to perform a self-initiated pro-social behavior, none of the children who were low on APT did. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Genetic and environmental influences on girls' and boys' gender-typed and gender-neutral values.

In this first investigation of genetic and environmental influences on children's values, 271 German twin pairs (50.2% boys) reported their values at ages 7–11 years using the Portrait Values Questionnaire (Schwartz & Rubel, 2005). We distinguished between gender-neutral (conservation vs. openness to change) and gender-typed (self-transcendence vs. self-enhancement) values. Boys differed from girls in the importance given to gender-typed benevolence, achievement, and power values. Gender-neutral values showed moderate (.34) and gender-typed values showed higher (.49) heritability, with nonshared environment and error accounting for the remaining variance. For both sexes, substantial genetic effects accounted for the importance children gave to their respective gender-stereotypical end of the self-transcendence versus self-enhancement dimension. However, dramatic sex differences emerged in the gender-atypical end of the distribution. For girls, low self-transcendence (high gender-atypical values) showed a large (.76) group heritability. For boys, gender-atypical values (high self-transcendence) showed no heritability and a modest (.10) shared environment effect. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Optimization of Potassium Dinitramide Preparation

The synthesis of potassium dinitramide (KDN), an intermediate in the ammonium dinitramide (ADN) synthesis, was optimized to reduce the costs of the ADN synthesis in order to facilitate competitiveness of this oxidizer with ammonium perchlorate (AP). The optimal conditions for the synthesis of KDN like feedstock molar ratio, nitration time, and temperature were determined. KDN was obtained in ca. 48 % yield. The modifications introduced allowed to reduce feedstock consumption and energy intensity of the process.