Scaling the Aspect Ratio of Nanoscale Closely Packed Silicon Vias by MacEtch: Kinetics of Carrier Generation and Mass Transport

Metal‐assisted chemical etching (MacEtch) has shown tremendous success as an anisotropic wet etching method to produce ultrahigh aspect ratio semiconductor nanowire arrays, where a metal mesh pattern serves as the catalyst. However, producing vertical via arrays using MacEtch, which requires a pattern of discrete metal disks as the catalyst, has often been challenging because of the detouring of individual catalyst disks off the vertical path while descending, especially at submicron scales. Here, the realization of ordered, vertical, and high aspect ratio silicon via arrays by MacEtch is reported, with diameters scaled from 900 all the way down to sub‐100 nm. Systematic variation of the diameter and pitch of the metal catalyst pattern and the etching solution composition allows the extraction of a physical model that, for the first time, clearly reveals the roles of the two fundamental kinetic mechanisms in MacEtch, carrier generation and mass transport. Ordered submicron diameter silicon via arrays with record aspect ratio are produced, which can directly impact the through‐silicon‐via technology, high density storage, photonic crystal membrane, and other related applications.     

Crystal structure of the bacterial ribosomal decoding site complexed with a synthetic doubly functionalized paromomycin derivative: a new specific binding mode to an a-minor motif enhances in vitro antibacterial activity

The crystal structure of the complex between oligonucleotide containing the bacterial ribosomal decoding site (A site) and the synthetic paromomycin analogue 1, which contains the gamma-amino-alpha-hydroxybutyryl (L-haba) group at position N1 of ring II (2-DOS ring), and an ether chain with an O-phenethylaminoethyl group at position C2' of ring III, is reported. Interestingly, next to the paromomycin analogue 1 specifically bound to the A site, a second molecule of 1 with a different conformation is observed at the crystal packing interface which mimics the A-minor interaction between two bulged-out adenines from the A site and the codon-anticodon stem of the mRNA-tRNA complex. Improved antibacterial activity supports the conclusion that analogue 1 might affect protein synthesis on the ribosome in two different ways: 1) specific binding to the A site forces maintenance of the "on" state with two bulged out adenines, and 2) a new binding mode of 1 to an A-minor motif which stabilizes complex formation between the ribosome and the mRNA-tRNA complex regardless of whether the codon-anticodon stem is of the cognate or near-cognate type.     

Study of Magnetic and Electrical Properties of Poly(o-phenylenediamine)/Manganese Substituted ZnFe2O4 Nanocomposites

Journal of Inorganic and Organometallic Polymers and Materials - Different concentrations of ZnFe2O4 and manganese substituted ZnFe2O4 nanoparticles (10%, 20% and 30%) dispersed...     

Reliable nonfragile tracking control for switched systems with external disturbances

With the assistance of reliable control technique, the nonfragile tracking problem has been proposed in this paper for a class of switched systems with external disturbances under the aegis of modified repetitive controller. Notably, the designed repetitive controller is used to improve the tracking performance of the addressed switched systems. Preciously, the influence of external disturbances are estimated through the improved equivalent-input-disturbance strategy, wherein the effect caused by the external disturbances to the output channel are reduced by the aid of modified repetitive control strategy. The fundamental intention of this control synthesis is that the output of the system precisely tracks the reference signal even in the presence of external disturbances and gain fluctuations. For that cause, Lyapunov stability technique in conjunction with average dwell time approach is implemented to obtain adequate conditions in the shape of linear matrix inequalities which insists the exponential stability for the addressed system. Ultimately, the efficiency and supremacy of the proposed control schemes are justified via two numerical examples, wherein it is exposed to view that the developed control strategy is capable of good tracking performance and also estimates the external disturbances efficiently.     

Synthesis and characterization of aromatic/cycloaliphatic poly(amide‐ imide‐imide)s from bis(4‐amino‐ 3,5‐dimethylphenyl) cycloalkane derivatives

A series of novel aromatic diamines containing cycloaliphatic moieties was synthesized by the reaction of cycloalkanones like cyclohexanone and cycloheptanone with 2,6‐dimethylaniline. The tetrimide diacid was synthesized using the prepared diamine with 3,3′,4,4′‐benzophenonetetracarboxylic acid dianhydride/pyromellitic dianhydride and p‐aminobenzoic acid. The polymers were prepared by treating the tetrimide diacid with different aromatic diamines. The structures of the monomers and polymers were identified using elemental analysis and Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopy. The polymers show excellent solubility. The polymers are amorphous and have high optical transparency. They also show good thermal stability and their T_g value is found to be in the range 268–305 °C. Copyright © 2007 Society of Chemical Industry     

Synthesis,characterization and properties of photoresponsive polymers comprising photocrosslinkable pendant chalcone moieties

New methacrylate monomers, namely 4‐methacryloyloxyphenyl‐4′‐fluorostyryl ketone and 4‐methacryloyloxyphenyl‐4′‐ethylstyryl ketone comprising a free radical polymerizable group and a photocrosslinkable group, were synthesized by reacting the respective hydroxychalcones with methacryloyl chloride in the presence of triethylamine. The monomers were polymerized in the presence of ethyl methyl ketone (EMK) at 70 °C using benzoyl peroxide as the initiator. The chemical structures were characterized using various spectroscopic techniques: ultraviolet, Fourier transform infrared, ¹H NMR and ¹³C NMR. The thermal stability of the polymers was studied using thermogravimetric analysis in nitrogen atmosphere. Differential scanning calorimetry was used to determine the glass transition temperature of the homopolymers. Photocrosslinking of the synthesized homopolymers was investigated in solution. The two homopolymers were crosslinked within 10–15 min. After crosslinking, the homopolymers were insoluble in the same solvent. Copyright © 2006 Society of Chemical Industry     

Synthesis and characterisation of organosoluble polyimides containing the anisyl moiety

A new type of diamine monomer containing the anisyl moiety was synthesized via a straight‐forward one‐step procedure. Anisaldehyde was reacted with 2,6‐dimethylaniline in the presence of dry HCl to attain bis(4‐amino‐3,5‐dimethylphenyl)anisylmethane. A series of organo‐soluble polyimides were prepared using the anisyl diamine and various aromatic dianhydrides via a two step method involving thermal imidization. All polyimides are soluble in strong polar solvents such as N‐methyl‐2‐pyrollidone, N,N‐Dimethylformamide, and N,N‐DimethylAcetamide. The polyimides show excellent thermal stability and good mechanical properties. The glass transition temperatures of the polyimides are in the range 265–294 °C. The tensile strengths are in the range 79–99 MPa and the temperatures at which 10 % weight loss occurs are in the range 460–496 °C. Copyright © 2004 Society of Chemical Industry