Field enhancement of omega-shaped-gated poly-Si TFT SONOS memory fabricated by a simple sidewall spacer formation

A novel omega-shaped-gated (Ω-Gate) poly-Si thin-film-transistor (TFT) silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile memory devices fabricated with a simple process have been proposed for the first time. The Ω-Gate structure inherently covered two sharp corners manufactured simply via a sidewall spacer formation. Due to the sharp corner geometry, the local electric fields across the tunneling oxide could be enhanced effectively, thus improving the memory performance. Based on this field enhanced scheme, the Ω-Gate TFT SONOS revealed excellent program/erase (P/E) efficiency and larger memory window as compared to the conventional planar (CP) counterparts. In addition, owing to the better gate controllability, the Ω-Gate TFT SONOS also exhibited superior transistor performance with a much higher on-current, smaller threshold voltage, and steeper subthreshold swing. Therefore, such an Ω-Gate TFT SONOS memory is very promising for the embedded flash on the system-on-panel applications.     

Dependence of apparent resistance of four-electrode probes on insertion depth

The apparent resistance of a finite-thickness layer measured with a four-electrode plunge probe depends on the electrode insertion depth, electrode spacing, and layer thickness, as well as the resistivity ratio of an underlying layer. A physical model consisting of air, a saline solution layer, and an agar layer simulates the real situation of resistivity measurement. The saline layer represents the finite-thickness layer whose resistivity is to be measured by a plunge electrode probe, and the agar layer represents an underlying perturbing layer. A micropositioner controls the insertion depth of the four electrodes into the saline solution. With the apparent resistance measured on a semi-infinite-thickness layer of saline solution as standard, measurement results show decreasing apparent resistance and increasing error with increasing electrode insertion depth. This information is important for correct measurement of myocardial resistivity in vivo and in vitro.     

Analysis of passively Q-switched lasers with simultaneous modelocking

Simultaneous Q-switching and modelocking in a diode-pumped Nd:YAG/Cr⁴⁺:YAG laser is experimentally demonstrated. A general recurrence is derived for the analysis of the temporal shape of a single Q-switched envelope with mode locked pulse trains. With the developed model, the modelocked pulse energy and the total Q-switched pulse energy can be calculated. Excellent agreement was found between the present results and detailed theoretical computations     

Design of the QoS framework for the IEEE 802.16 mesh networks

IEEE 802.16 (WiMax) technology is designed to support broadband speeds over wireless networks for the coming era of broadband wireless access (BWA). IEEE 802.16 is expected to provide transmission of high‐rate and high‐volume multimedia data streams for fixed and mobile applications. As an extension of point‐to‐multipoint (PMP) configuration, the IEEE 802.16 mesh mode provides a quicker and more flexible approach for network deployment. Multimedia networking requires quality‐of‐service (QoS) support, which demands elaborate mechanisms in addition to the four service types defined in the specification. By examining standard centralized and distributed scheduling/routing schemes in the mesh mode from QoS aspect, a BS‐controlled and delay‐sensitive scheduling/routing scheme is proposed in the paper. Associate mechanisms including admission control, flow setup and link state monitoring are also proposed. Integration of the proposed mechanisms is presented as a complete QoS framework. Simulation study has demonstrated that the average delay as well as the delay jitters per hop in the proposed scheme is smaller than that of the distributed scheme and much smaller than that of the centralized scheme. Furthermore, proposed mechanisms can also achieve higher throughput than the contrasts and generate much smaller signaling overhead, making the proposed framework a promising scheme for multimedia support in the IEEE 802.16 mesh network. Copyright © 2009 John Wiley & Sons, Ltd.     

Performance comparisons between PCA-EA-LBG and PCA-LBG-EA approaches in VQ codebook generation for image compression

The aim of this study is to generate vector quantisation (VQ) codebooks by integrating principle component analysis (PCA) algorithm, Linde-Buzo-Gray (LBG) algorithm, and evolutionary algorithms (EAs). The EAs include genetic algorithm (GA), particle swarm optimisation (PSO), honey bee mating optimisation (HBMO), and firefly algorithm (FF). The study is to provide performance comparisons between PCA-EA-LBG and PCA-LBG-EA approaches. The PCA-EA-LBG approaches contain PCA-GA-LBG, PCA-PSO-LBG, PCA-HBMO-LBG, and PCA-FF-LBG, while the PCA-LBG-EA approaches contain PCA-LBG, PCA-LBG-GA, PCA-LBG-PSO, PCA-LBG-HBMO, and PCA-LBG-FF. All training vectors of test images are grouped according to PCA. The PCA-EA-LBG used the vectors grouped by PCA as initial individuals, and the best solution gained by the EAs was given for LBG to discover a codebook. The PCA-LBG approach is to use the PCA to select vectors as initial individuals for LBG to find a codebook. The PCA-LBG-EA used the final result of PCA-LBG as an initial individual for EAs to find a codebook. The search schemes in PCA-EA-LBG first used global search and then applied local search skill, while in PCA-LBG-EA first used local search and then employed global search skill. The results verify that the PCA-EA-LBG indeed gain superior results compared to the PCA-LBG-EA, because the PCA-EA-LBG explores a global area to find a solution, and then exploits a better one from the local area of the solution. Furthermore the proposed PCA-EA-LBG approaches in designing VQ codebooks outperform existing approaches shown in the literature.     

Thermal reliability and performances of InGaP schottky contact with Cu/Au and Au/Cu-MSM photodetectors

We report the Schottky performance and thermal reliability of a wide bandgap InGaP layer in contact with a Cu/Au metallic system. An effective Schottky barrier height of 0.97 eV and an ideality factor of 1.21 can be achieved. The thermal reliability of the resultant Schottky barrier diodes was analyzed using Auger electron spectroscopy and atomic force microscopy. The thermal reliability could be main tained up to 450°C. The failure mechanism was attributable to the decomposition of the InGaP layer and the interdiffusion of the chemical elements at higher temperature. Insensitive photoresponsivity with the in cident optical power was found for the resultant Au/Cu-metal-semiconductor-metalphotodetectors (MSM-PDs). According to the measured temporal response of the Au/Cu-MSM-PDs, the operation frequency could be above 10 GHz.     

Perturbed-TEM analysis of transmission lines with imperfectconductors

A perturbed-transverse electromagnetic (TEM) approach to studying the detailed current distribution and the propagation constant of a multiconductor transmission line system with imperfect conductors is discussed. The perturbed fields are derived assuming that the fields outside the conductors are TEM waves of the corresponding lossless system and those inside the conductors satisfy the transverse magnetic (TM) modal equations. These fields are then inserted into a perturbational formula to obtain the propagation constant of the lossy system. The current distribution and the propagation constant (which clearly illustrates the loss mechanism due to the skin effect and the proximity effect) of a lossy two-wire system are presented as an example     

A Novel Pt/In0.52Al0.48As Schottky Diode-Type Hydrogen Sensor

On the basis of a Pt/In_0.52Al_0.48As metal-semiconductor structure, a novel hydrogen sensor is fabricated and demonstrated. The studied Pt/In_0.52Al_0.48As Schottky diode-type hydrogen sensor exhibits significant sensing performance including high relative sensitivity ratio of about 2600% (under the 1% H₂/air gas and V_R=-0.5 V at 30 degC), large current variation of 310 muA (under the 1% H₂/air gas and V_R=-5 V at 200 degC), widespread reverse-voltage regime (0~-5 V), stable hydrogen-sensing current-voltage (I-V) curves, and fast transient response time of 1.5 s. The calculated Schottky barrier-height change and series-resistance variation, from the thermionic-emission model and Norde method, are 87.0 meV and 288 Omega, respectively (under the 1% H₂/air gas at 30 degC). The hydrogen concentrations and operating temperatures tested in this letter are in the range of 15 ppm-1% H₂/air and 30 degC-250 degC, respectively. Based on the excellent integration compatibility with InP-based electronic devices, the studied device provides the potentiality in high-performance sensor-array applications     

Secure Handover Authentication Protocol Based on Bilinear Pairings

Handover authentication protocol enables a mobile node to switch from one base station to another without loss or interruption of service when the node exits the transmission area of his or her current base station. This paper proposes a secure prime-order handover authentication protocol based on bilinear pairings. The proposed protocol adapts the concept of pseudonyms to provide user anonymity and user unlinkability. It withstands well-known security threats and achieves mutual authentication, user unlinkability. A batch signature verification mechanism to verify a mass of signatures is presented in our scheme. We also prove that our scheme is secure under random oracle.     

Mixed Broadcast Techniques of Leisure Information in Vehicular Ad-Hoc Networks

Telecommunication Systems - Vehicle-to-vehicle communication and probabilistic broadcast are important means for information dissemination in vehicular ad-hoc networks (VANETs). In contrast to...