Isothermal and non-isothermal C-V trap measurements—A critical comparison

A comparative study was made of isothermal and non-isothermal C-V methods for characterization of deep levels in semiconductors using Schottky contacts. Though these methods are in principle equivalent the requirements of manageable data reduction and conveniently realizable experimental accuracy put the non-isothermal methods at a disadvantage. A computer simulation of the non-isothermal approach shows that a commonly made simplification relating to the motion of the Fermi level with temperature has only a relatively minor effect on the trap energies, but causes order of magnitude errors in the capture cross sections. The difficulties in obtaining trap energies with this method in certain cases are of an experimental nature. The problems arising in detecting different levels at the same sample and in profiling are discussed.     

Control structure selection of increased-pressure extractive distillation process for DMC-MeOH azeotropic mixture

Producing dimethyl carbonate (DMC) as a green chemical with the desired purity is important in the industry. Although studies on the steady-state design of energy-efficient extractive distillation processes are important for the purification of DMC-methanol (DMC-MeOH) azeotropic mixtures, the dynamic controllability of these processes is also critical in the case of feed condition changes, and it should be investigated carefully. Results of the limited studies in the literature show that changing the operating pressures in extractive distillation processes might have different effects on the dynamic controllability of different systems. Thus, in this study, alternative control strategies are developed for a recently proposed increased-pressure extractive distillation process to separate DMC-MeOH mixture. All control structures are designed using inferential temperature controllers, which have a general acceptance in industrial applications. Effects of different ratio controllers are investigated by evaluating the dynamic responses of control structures for disturbances in feed flowrate and composition. Two metrics including integral absolute error and steady-state deviation of purities are used in the evaluation of alternatives. Results of dynamic simulations show that a control structure including reflux ratio controller is not a suitable strategy for this process. It is demonstrated that a control structure including reflux to feed ratio controller for both distillation columns is necessary for the robust and efficient control of a pressure-increased extractive distillation process. These efficient dynamic results support the economic advantage of increased-pressure extractive distillation process separating DMC-MeOH azeotropic mixtures.     

Dual-Antenna RF CMOS Front-End for Interferer Removal in Ultra-Wideband Systems

Many ultra-wideband (UWB) systems are challenged by strong jammers and narrowband interferers. Using two antennas, we demonstrate a robust UWB radio frequency (RF) front-end design in a 0.25 μm mixed-signal complementary metal oxide semiconductor (CMOS) technology. The proposed realization is capable of adaptively removing a high-power, narrowband interferer early in the receiver chain avoiding front-end saturation and preserving UWB signal power. The early interferer removal resulting in interferer-free demodulation is based on the least mean squares (LMS) algorithm and achieved through a novel combiner low-noise amplifier and noise optimized filtering. Circuit level RF simulations of the proposed circuitry indicate a maximum improvement in signal-to-interference ratio of 39.6 dB.     

Spline smoothing for experimental data under zero median of the noise

We propose an algorithm for computing parameter estimates for a smoothing cubic spline that minimize the estimated expectation of losses. Instead of the usual assumption that the noise is centered we use an assumption which is more realistic for many practical smoothing problems, namely that it is zero median. The problem setting is augmented by prior deterministic information in the form of constraints on linear combinations of parameters of spline functions. We obtain explicit representations of such estimates and give their qualitative interpretation. Based on the results of a numerical experiment, we establish a high degree of robustness of the solutions to the presence of outliers in the measurements, including same sign outliers, and the possibility to fairly reliably determine the actual accuracy of the resulting estimates of spline parameters by the attained minimum risk value.     

Quantitative determination of electric field strengths within dynamically operated devices using EBIC analysis in the SEM

Although electron beam-induced current (EBIC) technique was invented in the seventies, it is still a powerful technique for failure analysis and reliability investigations of modern materials and devices. Time-resolved and stroboscopic microanalyses using sampling Fourier components decomposed by modulated charge carrier excitation are introduced. Quantitative determination of electric field strengths within dynamically operated devices in the scanning electron microscope (SEM) will be demonstrated. This technique allows investigations of diffusion and drift processes and of variations of electric field distributions inside active devices.     

Spectrally resolved cathodoluminescence analyses in the optical near-field

By implementing a scanning near-field optical microscope into the specimen chamber of a scanning electron microscope, cathodoluminescence can be locally detected in the optical near-field. The achievable spatial resolution in this set-up is only limited by the size of the aperture in a coated fibre probe and its separation from the sample, rather than by the energy dissipation volume of the primary electrons and diffusion processes of excess carriers inside the specimen. We demonstrate how electronically active defects in polycrystalline diamond can be distinguished and localized with sub-wavelength lateral resolution by spectral filtering of the cathodoluminescence signal.     

Energy use in two Italian and Chinese tile manufacturers: A comparison using an enterprise input–output model

It is becoming evident that sustainable development methods are now being considered by governments and corporations from all countries at both local and global level. Firms are increasingly looking to strike a balance between profit, preserving the local environment, and energy savings, rather than just looking for profit. In this paper, an enterprise input–output analysis based on production processes is used to investigate two tile manufacturers, one located in China and the other in Italy. The aim of the paper is to describe their energy/materials use and consequent pollution/waste emissions, and to make a comparison between them. As this industry uses huge quantities of energy, it is useful to monitor these consumption uses along with pollution levels. This accounting can help in planning future local development strategies that would make production cycles more efficient and sustainable.     

Simultaneous growth of self-patterned carbon nanotube forests with dual height scales

In this study, we report on a unique, one-step fabrication technique enabling the simultaneous synthesis of vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with dual height scales through alcohol catalyzed chemical vapor deposition (ACCVD). Regions of VA-MWCNTs with different heights were well separated from each other leading to a self-patterning on the surface. We devised a unique layer-by-layer process for application of catalyst and inhibitor precursors on oxidized Si (100) surfaces before the ACCVD step to achieve a hierarchical arrangement. Patterning could be controlled by adjusting the molarity and application sequence of precursors. Contact angle measurements on these self-patterned surfaces indicated that manipulation of these hierarchical arrays resulted in a wide range of hydrophobic behavior changing from that of a sticky rose petal to a lotus leaf.     

Effect of Supercritical Ethanol Drying on the Properties of Zinc Oxide Nanoparticles

The synthesis, characterization, and application as polymers and anti-wear additives of nanosized zinc oxide particles obtained by conventional and supercritical ethanol drying are reported in this study. The nanaoparticles of ZnO produced by the two different drying techniques were characterized using Fourier Transform Infrared (FT-IR) spectrophotometry, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Thermogravimetric analysis (TGA) to elucidate the shape, size, composition, and stability of the nanoparticles. ZnO nanoparticles were then applied to poly (vinyl chloride) (PVC) powder and light mineral oil to assess their effectiveness and suitability as additives in diverse areas. XRD analysis revealed ZnO crystalline structure with average particle size of 24.7 nm for zinc oxide nanoparticles prepared by supercritical ethanol drying while SEM showed well-isolated and monodisperse particles with average size of 61.08 nm.