2005年及以后KrF深紫外线光源的发展趋势-多功能和可扩展性

深紫外线光刻技术利用KrF激光作为光源,该技术在半导体行业的应用已进入第10年.为满足行业对更高生产力的需求,KrF光源从早期的10W产品发展到以Cymer ELS-7010为代表的40W最新一代产品.就像前几代一样,输出光谱和剂量性能是随着照射工具的光学和分级技术的进步而改进,目前CD分辨率可以达到90 nm甚至更加精细.2005年,将有超过75%的新KrF DUV设备进入亚洲市场,KrF光源技术在这个地区将会受到大量关注.但是,随着KrF扫描仪的技术日渐成熟,KrF光源的未来前景会如何呢?     

From Bulk to Monolayer MoS2: Evolution of Raman Scattering

Molybdenum disulfide (MoS₂) is systematically studied using Raman spectroscopy with ultraviolet and visible laser lines. It is shown that only the Raman frequencies of and peaks vary monotonously with the layer number of ultrathin MoS₂ flakes, while intensities or widths of the peaks vary arbitrarily. The coupling between electronic transitions and phonons are found to become weaker when the layer number of MoS₂ decreases, attributed to the increased electronic transition energies or elongated intralayer atomic bonds in ultrathin MoS₂. The asymmetric Raman peak at 454 cm^?1, which has been regarded as the overtone of longitudinal optical M phonons in bulk MoS₂, is actually a combinational band involving a longitudinal acoustic mode (LA(M)) and an optical mode ( ). Our findings suggest a clear evolution of the coupling between electronic transition and phonon when MoS₂ is scaled down from three‐ to two‐dimensional geometry.     

Thermoelectric Properties of Pulsed Electric Current Sintered Samples of AgPb m SbSe17 (m?=?16 or 17)

Lead chalcogenide materials have drawn attention in recent years because of their outstanding thermoelectric properties. Bulk n-type materials of AgPb _m SbTe_2+m have been reported to exhibit high figure of merit, ZT, as high as 1.7 at 700?K. Recent reports have shown p-type lead selenide-based compounds with comparable ZT. The analogous material AgPb _m SbSe₁₇ shares a similar cubic rock-salt structure with PbTe-based compounds; however, it exhibits a higher melting point, and selenium is more abundant than tellurium. Using solid solution chemistry, we have fabricated cast AgPb₁₅SbSe₁₇ samples that show a peak power factor of approximately 17???W/cm?K² at 450?K. Increasing the strength of such materials is commonly achieved through powder processing, which also helps to homogenize the source materials. Pulsed electric current sintering (PECS) is a hot-pressing technique that utilizes electric current through the die and sample for direct Joule heating during pressing. The mechanisms present during PECS processing have captured significant research interest and have led to some notable improvements in sample properties compared with other densification techniques. We report the thermoelectric properties of PECS samples of AgPb _m SbSe₁₇ along with sample fabrication and processing details.     

Modeling,control, and analysis of a robotic assist device

This paper presents a model-based approach to control design for an existing lower-limb robotic assist device, the portable powered ankle–foot orthosis (PPAFO). This approach seeks to address two key limitations of the PPAFO caused by the use of solenoid valves: slow system response and inefficient actuation during assistance. System limitations were addressed using a proportional valve coupled with a modified control approach. The two different system configurations were compared in simulation and on an experimental test fixture during motion and torque control tasks. Root mean square (RMS) trajectory tracking error was used to evaluate system performance, while system efficiency was assessed by measuring pneumatic fuel consumed during each task. The proportional valve system reduced RMS tracking error by as much as 91%, and increased efficiency by as much as 95% over the solenoid valve system.     

A stochastic control approach to optimally designing hierarchical flash sets in P300 communication prostheses

The P300-based speller is a well-established brain-computer interface for communication. It displays a matrix of objects on the computer screen, flashes each object in sequence, and looks for a P300 response induced by flashing the desired object. Most existing P300 spellers uses a fixed set of flash objects. We demonstrate that performance can be significantly improved by sequential selections from a hierarchy of flash sets containing variable number of objects. Theoretically, the optimal hierarchy of flash sets--with respect to a given statistical language model--can be found by solving a stochastic control problem of low computational complexity. Experimentally, statistical analysis demonstrates that the average time per output character at 85% accuracy is reduced by over 50% using our variable-flash-set approach as compared to traditional fixed-flash-set spellers.     

Design and validation of a fully implantable, chronic, closed-loop neuromodulation device with concurrent sensing and stimulation

Chronically implantable, closed-loop neuromodulation devices with concurrent sensing and stimulation hold promise for better understanding the nervous system and improving therapies for neurological disease. Concurrent sensing and stimulation are needed to maximize usable neural data, minimize time delays for closed-loop actuation, and investigate the instantaneous response to stimulation. Current systems lack concurrent sensing and stimulation primarily because of stimulation interference to neural signals of interest. While careful design of high performance amplifiers has proved useful to reduce disturbances in the system, stimulation continues to contaminate neural sensing due to biological effects like tissue-electrode impedance mismatch and constraints on stimulation parameters needed to deliver therapy. In this work we describe systematic methods to mitigate the effect of stimulation through a combination of sensing hardware, stimulation parameter selection, and classification algorithms that counter residual stimulation disturbances. To validate these methods we implemented and tested a completely implantable system for over one year in a large animal model of epilepsy. The system proved capable of measuring and detecting seizure activity in the hippocampus both during and after stimulation. Furthermore, we demonstrate an embedded algorithm that actuates neural modulation in response to seizure detection during stimulation, validating the capability to detect bioelectrical markers in the presence of therapy and titrate it appropriately. The capability to detect neural states in the presence of stimulation and optimally titrate therapy is a key innovation required for generalizing closed-loop neural systems for multiple disease states.     

Low‐Temperature Growth of SnO2 Nanorod Arrays and Tunable n–p–n Sensing Response of a ZnO/SnO2 Heterojunction for Exclusive Hydrogen Sensors

Uniform SnO₂ nanorod arrays have been deposited at low temperature by plasma‐enhanced chemical vapor deposition (PECVD). ZnO surface modification is used to improve the selectivity of the SnO₂ nanorod sensor to H₂ gas. The ZnO‐modified SnO₂ nanorod sensor shows a normal n‐type response to 100 ppm CO, NH₃, and CH₄ reducing gas whereas it exhibits concentration‐dependent n–p–n transitions for its sensing response to H₂ gas. This abnormal sensing behavior can be explained by the formation of n‐ZnO/p‐Zn‐O‐Sn/n‐SnO₂ heterojunction structures. The gas sensors can be used in highly selective H₂ sensing and this study also opens up a general approach for tailoring the selectivity of gas sensors by surface modification.     

The financials of constructing a solar PV for net-zero energy operations on college campuses

The LACCD has a goal of establishing net-zero energy operations across its nine campuses. The project faces many challenges, including limited open areas for installing solar PV, increasing energy consumption challenges associated with campus energy growth and the high cost of installing solar PV. A previous study by Kwan and Hoffmann (2010) found that the LACCD would need to install a 9.5 MW solar PV array in order to meet total campus energy demand on a college campus through the year 2020. This paper attempts to evaluate the financial feasibility of such a project, taking into account the current local, state and federal renewable energy incentives available. We find that despite the availability of financial incentives by local municipal utility companies including installation rebates and net metering, the cost of electricity generated by solar PV still remains approximately 30% higher than electricity generated by fossil fuels. We also find that the optimal solar PV array size from a financial standpoint is one that is sized to generate and meet all electrical demand during sunlight hours. Any array larger than this yields diminishing returns. Finally our analysis examined the influence of per kW installation cost and found that only when prices dropped to $3.00 per installed watt did a net-zero energy solar PV array have an NPV of 0.     

Eye movements and word skipping during reading: Effects of word length and predictability.

Eye movements were monitored as subjects read sentences containing high- or low-predictable target words. The extent to which target words were predictable from prior context was varied: Half of the target words were predictable, and the other half were unpredictable. In addition, the length of the target word varied: The target words were short (4–6 letters), medium (7–9 letters), or long (10–12 letters). Length and predictability both yielded strong effects on the probability of skipping the target words and on the amount of time readers fixated the target words (when they were not skipped). However, there was no interaction in any of the measures examined for either skipping or fixation time. The results demonstrate that word predictability (due to contextual constraint) and word length have strong and independent influences on word skipping and fixation durations. Furthermore, because the long words extended beyond the word identification span, the data indicate that skipping can occur on the basis of partial information in relation to word identity. (PsycINFO Database Record (c) 2011 APA, all rights reserved)