Comparative physical and electrical metrology of ultrathin oxidesin the 6 to 1.5 nm regime

In this work, five methods for measuring the thickness of ultra-thin gate oxide layers in MOS structures were compared experimentally on n⁺ poly-SiO₂-p-Si structures. Three methods are based on electrical capacitance-voltage (C-V) and current-voltage (I-V) data and the other two methods are HRTEM and optical measurement. MOS capacitors with oxide thickness in the range 17-55 Å have been used in this study. We found that thickness extracted using QM C-V and HRTEM agree within 1.0 Å over the whole thickness range when a dielectric constant of 3.9 was used. Comparison between thickness extracted using quantum interference (QI) I-V technique and optical measurement were also within 1.0 Å for thickness 31-47 Å. However, optical oxide thickness was consistently lower than the TEM thickness by about 2 Å over the thickness range under consideration. Both optical measurement and QM C-V modeling yield the same thickness as the nominal oxide thickness increases (>50 Å)     

Information theoretic considerations for coded modulation overfading channels

We compute the random coding error exponent for coded modulation transmitted over a flat, memoryless, Rayleigh fading channel. In addition, estimates of code lengths required to achieve a certain error probability are determined and compared to those required for the additive white Gaussian noise channel. Finally, the effect of receiver antenna diversity is also considered as a method to compensate for fading and is shown to have a significant, positive impact on the error exponent. The results we obtain represent an information theoretic view that complements the existing literature on the performance of coded modulation over fading channels with receiver diversity     

Cons and pros: prison education through the eyes of the prison educated*

ABSTRACT

While much has been written within academic journals about prisoners, rarely is there anything written by prisoners. In this essay, we, a group of prisoners who are earning or have earned college degrees while incarcerated in Texas, address the purpose, merits, and pitfalls of prison education and reform. Written as a response to the essays appearing in this special issue, we discuss our experiences of being othered as inmates, the impact of societal bias against us, our perspectives on prison education, and our own ideas for reforming prisons and making them more humane.     

Capacity and interference statistics of highways W-CDMAcigar-shaped microcells (uplink analysis)

The capacity and the interference statistics of the sectors of the shaped W-CDMA cell are studied. A model of five cells is used to analyze the uplink. The cells are assumed to exist in rural zones. The capacity and the interference statistics of the cell are studied using a two-slope propagation model. The expected value and the variance of the interference are given for different propagation exponent     

Efficient Self‐Assembly Synthesis of Uniform CdS Spherical Nanoparticles‐Au Nanoparticles Hybrids with Enhanced Photoactivity

The treatment of environmental pollution has become one of the most critical issues in the world. Despite the progress made in the study of semiconductor photocatalysis, it is still a challenge to obtain photocatalysts with high activity through relatively simple fabrication processes. In this work, monodisperse CdS spherical nanoparticles (SNPs) of various sizes and good crystallinity are obtained by only adjusting the starting ratio of reactants and the reaction temperature, exhibiting high photocatalytic performances. The photocatalytic rate constant of the ≈ 100 nm CdS SNPs, especially, is more than double that of P25. Furthermore, 3‐mercaptopropyltrimethoxysilane is used to assist the interaction between ≈ 200 nm CdS SNPs and citrate‐stabilized Au nanoparticles (NPs). The significant increase of photocatalytic activity is confirmed by the degradation of Rodamine B (RhB) under Xe light irradiation. At the optimal Au concentration (0.5 wt%), the prepared nanohybrids show the highest photocatalytic activity, exceeding that of pure CdS two times. The superior photocatalytic performances of the CdS SNPs‐Au nanohybrids can be attributed to the intimate interfacial contact between CdS SNPs and Au NPs, which is a contributing factor to the improvement of transfer and the fate of photogenerated charge carriers from CdS SNPs to Au NPs.     

Electrodeposited Cu2ZnSnSe4 thin film solar cell with 7% power conversion efficiency

High performance Cu₂ZnSnSe₄ (CZTSe) photovoltaic materials were synthesized by electrodeposition of metal stack precursors followed by selenization. A champion solar cell with 7.0% efficiency is demonstrated. This is the highest efficiency among all of the CZTSe solar cells prepared from electrodeposited metallic precursors reported to‐date. Device parameters are discussed from the perspective of material microstructure and composition in order to improve performance. In addition, a high performance electrodeposited CZTS (S only) solar cell was demonstrated and its device characteristics were compared against the CZTSe (Se only) cell. Using secondary ion mass spectrometry for the analysis of the chemical composition of the absorber layer, a higher concentration of oxygen in the electrodeposited absorber is thought to be the root cause of the lower performance of the electrodeposited CZTS or CZTSe solar cells with respect to a solar cell fabricated by evaporation. The grain boundary areas of Sn‐rich composition are thought to be responsible for the lower shunt resistance commonly observed in CZTSe devices. We measured the longest minority carrier lifetime of 18 ns among all reported kesterite devices. This work builds a good baseline for obtaining higher efficiency earth‐abundant solar cells, while it highlights electrodepositon as a low cost and feasible method for earth‐abundant thin film solar cell fabrication. Copyright © 2013 John Wiley & Sons, Ltd.     

Recursive least squares identification methods for multivariate pseudo-linear systems using the data filtering

This paper concerns the parameter identification methods of multivariate pseudo-linear autoregressive systems. A multivariate recursive generalized least squares algorithm is presented as a comparison. By using the data filtering technique, a multivariate pseudo-linear autoregressive system is transformed into a filtered system model and a filtered noise model, and a filtering based multivariate recursive generalized least squares algorithm is developed for estimating the parameters of these two models. The proposed algorithm achieves a higher computational efficiency than the multivariate recursive generalized least squares algorithm, and the simulation results prove that the proposed method is effective.     

Project Oriented Problem Based Learning: A Wireless Sensor Network Perspective

Every nation rely on latest engineering technologies to foster in today’s technological era. Wireless Sensor Networks (WSNs) is one of the latest emerging technologies being the center of interest of today’s researchers. All the researchers work hard to produce quick deliverables through Research and Development (RandD) and by applying different learning pedagogues. Currently, the learning pedagogues in Engineering RandD are Project Based Learning and Problem Based Learning (PBL). Based on these pedagogues, this paper propose and implements a hybrid pedagogy called Project Oriented PBL (PO-PBL) which is time effective and result oriented learning pedagogy. It has resulted in providing impetus to RandD in WSNs. Further the proposed pedagogy is divided into two paradigms namely PO-PBL Macro Model and PO-PBL Micro Model. We observed that PO-PBL Macro Model results in optimal number of deliverables in time restricted manner over large scale. Moreover, we have also implemented PO-PBL Micro Model, compared it with PO-PBL Macro Model and propose PO-PBL Micro Model as basis for designing self-learning algorithm for WSNs devices.     

A 50-MS/s (35 mW) to 1-kS/s (15 /spl mu/W) power scaleable 10-bit pipelined ADC using rapid power-on opamps and minimal bias current variation

A novel rapid power-on operational amplifier and a current modulation technique are used in a 10-bit 1.5-bit/stage pipelined ADC in 0.18-/spl mu/m CMOS to realize power scalability between 1 kS/s (15 /spl mu/W) and 50 MS/s (35 mW), while maintaining an SNDR of 54-56 dB for all sampling rates. The current modulated power scaling (CMPS) technique is shown to enhance the power scaleable range of current scaling by 50 times, allowing ADC power to be varied by a factor of 2500 while only varying bias currents by a factor of 50. Furthermore, the nominal power is reduced by 20%-30% by completely powering off the rapid power-on opamps during the sampling phase in the pipeline's sample-and-holds.     

The role of the mercury-Si Schottky-barrier height in /spl Psi/-MOSFETs

Pseudo-MOSFETs (/spl Psi/-MOSFET) are routinely used for silicon-on-insulator (SOI) material characterization, allowing threshold voltage, electron and hole mobility, doping density, oxide charge, interface trap density, etc. to be determined. The HgFET, one version of the /spl Psi/-MOSFET, uses mercury source and drain contacts. It is a very effective SOI test structure, but its current-voltage behavior is critically dependent on the Hg-Si interface. We have investigated this interface through current-voltage measurements of HgFETs and Schottky diodes and through device modeling. We show that modest barrier height changes of 0.2 eV lead to current changes of up to three orders of magnitude. Etching the Si surface in a mild HF :H/sub 2/O solution can easily change barrier heights and we attribute this behavior to Si surface passivation of dangling bonds. As this surface passivation diminishes with time, the Si surface becomes a more active generation site and the barrier height of the Hg-Si interface changes, taking on the order of 50-100 h at room temperature in air.