Low-energy electron-enhanced etching of HgCdTe

Low-energy electron-enhanced etching (LE4) is applied to HgCdTe to eliminate ion-induced surface damage. First, LE4 results for patterned samples are illustrated. The LE4 mechanism is understood from a mechanistic study in terms of three etch variables: direct current (DC) bias, gas composition, and sample temperature. For this paper, the effects of DC bias (electron energy) and gas composition (CH₄ concentration) are summarized qualitatively, followed by quantitative evidence. Etch rate, the amount of polymer, surface stoichiometry, and surface roughness have specific relations with each etch variable under competition between pure LE4 and polymer deposition.     

晶圆测试探针新的测试价值

晶圆测试探针曾被认为是节约废芯片封装成本的一种方法,现今它却成为工艺控制、成品率管理、产品质量以及总测试成本的一个关键因素。此外,随着组装相关的故障测试之后,封装水准晶圆分选的完全测试不久将会来临。     

Supervised learning and frequency domain averaging-based adaptive channel estimation scheme for filterbank multicarrier with offset quadrature amplitude modulation

Filterbank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) is an attractive alternative to the orthogonal frequency division multiplexing (OFDM) modulation technique. In comparison with OFDM, the FBMC-OQAM signal has better spectral confinement and higher spectral efficiency and tolerance to synchronization errors, primarily due to per-subcarrier filtering using a frequency-time localized prototype filter. However, the filtering process introduces intrinsic interference among the symbols and complicates channel estimation (CE). An efficient way to improve the CE in FBMC-OQAM is using a technique known as windowed frequency domain averaging (FDA); however, it requires a priori knowledge of the window length parameter which is set based on the channel's frequency selectivity (FS). As the channel's FS is not fixed and not a priori known, we propose a k-nearest neighbor-based machine learning algorithm to classify the FS and decide on the FDA's window length. A comparative theoretical analysis of the mean-squared error (MSE) is performed to prove the proposed CE scheme's effectiveness, validated through extensive simulations. The adaptive CE scheme is shown to yield a reduction in CE-MSE and improved bit error rates compared with the popular preamble-based CE schemes for FBMC-OQAM, without a priori knowledge of channel's frequency selectivity.     

Should mobile Internet be an extension to the fixed web? Fixed-mobile reinforcement as mediator between context of use and future use

As the fixed and mobile Internet are converging, the question emerges whether consumers expect mobile Internet services to replicate services they know from the fixed Internet. Literature on reinforcement and displacement suggests that the use of new media depends on whether users are inclined to replace or reinforce their existing media use on a new device. This paper analyzes whether the importance that users attribute to using similar services on their mobile phone as on the fixed Internet can explain the intention to adopt mobile services. Specifically, we investigate if such fixed-mobile reinforcement could mediate the impact of personal innovativeness and several dimensions of context. We compare basic Internet services, entertainment services and transaction services. We find that especially the intention to adopt basic Internet services largely depends on the importance of using similar services in the mobile domain as on the fixed Internet. Several context-of-use predictors are partially or even fully mediated by fixed-mobile reinforcement. The results convey a positive message to operators that are betting on converged multimedia services that can be accessed from any device and from any fixed or mobile network.     

An instant-switching ?–Σ fractional-N frequency synthesizer with adjustable duty cycles

A Phase-Locked Loop (PLL)-based frequency synthesizer (FS) with adjustable duty cycle is presented. By employing digital processing circuitry and the ??C?? fractional-N technique, the FS is capable of generating arbitrary frequencies in a wide frequency range, and capable of adjusting the clock duty cycles. In addition, the switching between different frequencies is instant except when a very fine frequency resolution is required. The adjustable duty cycle and instant switching are desired features in applications such as time-interleaved Analog-to-Digital-Converters (ADCs), switched-capacitor circuits, and DC?CDC converters. The design was fabricated using a 0.13???m CMOS process. This paper gives the theories, analysis, implementation, and measurement results of this FS.     

Photovoltaics literature survey (no. 6)

In order to help keep readers up‐to‐date in the field each issue of Progress in Photovoltaics will contain a list of recently published journal articles most relevant to its aims and scope. This list is drawn primarily from recent issues of IEEE Transactions on Electron Devices, Journal of Applied Physics, Progress in Photovoltaics, Solar Energy and Solar Energy Materials and Solar Cells, with additional journals surveyed if space permits. To assist the reader, the list is separated into broad categories, but please note that these classifications are by no means strict. Also note that inclusion in the list is not an endorsement of a paper's quality. If you have any suggestions please email Mark Keevers at m.keevers@unsw.edu.au Copyright © 2001 John Wiley & Sons, Ltd.     

Wear‐Resistant Nanoscale Silicon Carbide Tips for Scanning Probe Applications

The search for hard materials to extend the working life of sharp tools is an age‐old problem. In recent history, sharp tools must also often withstand high temperatures and harsh chemical environments. Nanotechnology extends this quest to tools such as scanning probe tips that must be sharp on the nanoscale, but still very physically robust. Unfortunately, this combination is inherently contradictory, as mechanically strong, chemically inert materials tend to be difficult to fabricate with nanoscale fidelity. Here a novel process is described, whereby the surfaces of pre‐existing, nanoscale Si tips are exposed to carbon ions and then annealed, to form a strong silicon carbide (SiC) layer. The nanoscale sharpness is largely preserved and the tips exhibit a wear resistance that is orders of magnitude greater than that of conventional silicon tips and at least 100‐fold higher than that of monolithic, SiO‐doped diamond‐like‐carbon (DLC) tips. The wear is well‐described by an atom‐by‐atom wear model, from which kinetic parameters are extracted that enable the prediction of the long‐time scale reliability of the tips.     

Transition Metal Oxide Work Functions: The Influence of Cation Oxidation State and Oxygen Vacancies

Transition metal oxides are capable of a wide range of work functions. This quality allows them to be used in many applications that involve charge transfer with adsorbed molecules, for example as heterogeneous catalysts, as charge‐injection layers in organic electronics, and as electrodes in fuel cells. Chemical and structural factors can alter transition‐metal oxide work functions, often making their work functions difficult to control. Little is known about the effects of the cation oxidation state and point defects on the oxide work function. It is necessary to understand how such chemical and structural factors affect work functions in order to controllably tune transition metal oxides for desired applications. Here, a correlation between the oxide work function and cation oxidation state is demonstrated. This correlation is attributed to the change in cation electronegativity with oxidation state. A model is presented that relates the work function to the oxygen deficiency for d⁰ oxides in the limit of dilute oxygen vacancies. It is proposed that the rapid initial decrease in work function, observed for d⁰ oxides, is caused by an increase in the density of donor‐like defect states. It is also shown that oxides tend to have decreased work functions near a metal/metal‐oxide interface as a consequence of the relationship between defects and work function. These insights provide guidelines for tuning transition metal oxide work functions.     

Linking Glass-Transition Behavior to Photophysical and Charge Transport Properties of High-Mobility Conjugated Polymers

The measurement of the mechanical properties of conjugated polymers can reveal highly relevant information linking optoelectronic properties to underlying microstructures and the knowledge of the glass transition temperature (T_g) is paramount for informing the choice of processing conditions and for interpreting the thermal stability of devices. In this work, we use dynamical mechanical analysis to determine the T_g of a range of state-of-the-art conjugated polymers with different degrees of crystallinity that are widely studied for applications in organic field-effect transistors. We compare our measured values for T_g to the theoretical value predicted by a recent work based on the concept of effective mobility ζ. The comparison shows that for conjugated polymers with a modest length of the monomer units, the T_g values agree well with theoretically predictions. However, for the near-amorphous, indacenodithiophene–benzothiadiazole family of polymers with more extended backbone units, values for T_g appear to be significantly higher, predicted by theory. However, values for T_g are correlated with the sub-bandgap optical absorption suggesting the possible role of the interchain short contacts within materials’ amorphous domains.     

Development and Simulation of Sulfur‐doped Graphene Supported Platinum with Exemplary Stability and Activity Towards Oxygen Reduction

Sulfur‐doped graphene (SG) is prepared by a thermal shock/quench anneal process and investigated as a unique Pt nanoparticle support (Pt/SG) for the oxygen reduction reaction (ORR). Particularly, SG is found to induce highly favorable catalyst‐support interactions, resulting in excellent half‐cell based ORR activity of 139 mA mg_Pt ^?1 at 0.9 V vs RHE, significant improvements over commercial Pt/C (121 mA mg_Pt ^?1) and Pt‐graphene (Pt/G, 101 mA mg_Pt ^?1). Pt/SG also demonstrates unprecedented stability, maintaining 87% of its electrochemically active surface area following accelerated degradation testing. Furthermore, a majority of ORR activity is maintained, providing 108 mA mg_Pt ^?1, a remarkable 171% improvement over Pt/C (39.8 mA mg_Pt ^?1) and an 89% improvement over Pt/G (57.0 mA mg_Pt ^?1). Computational simulations highlight that the interactions between Pt and graphene are enhanced significantly by sulfur doping, leading to a tethering effect that can explain the outstanding electrochemical stability. Furthermore, sulfur dopants result in a downshift of the platinum d‐band center, explaining the excellent ORR activity and rendering SG as a new and highly promising class of catalyst supports for electrochemical energy technologies such as fuel cells.