High thermal stability AlGaAs/InGaAs enhancement-mode pHEMT using palladium-gate technology

The dc, flicker noise, power, and temperature dependence of AlGaAs/InGaAs enhancement-mode pseudomorphic high electron mobility transistors (E-pHEMTs) were investigated using palladium (Pd)-gate technology. Although the conventional platinum (Pt)-buried gate has a high metal work function, which is beneficial for increasing the Schottky barrier height of the E-pHEMT, the high rate of intermixing of the Pt-GaAs interface owing to the effect of the continuous production of PtAs₂ on the device influenced the threshold voltage (V_th) and transconductance (g_m) at high temperatures or over the long-term operation. Variations in these parameters make Pt-gate E-pHEMT-related circuits impractical. Furthermore, a PtAs₂ interlayer caused a serious gate leakage current and unstable Schottky barrier height. This study presents the Pd-GaAs Schottky contact because Pd, an inert material with high work function of 5.12 eV. Stable Pd inhibited the less diffusion at high temperatures and simultaneously suppressed device flicker noise. The V_th of Pd/Ti/Au Schottky gate E-pHEMT was 0.183 V and this value shifted to 0.296 V after annealing at 200 °C. However, the V_th shifted from 0.084 to 0.231 V after annealing of the Pt/Ti/Au Schottky gate E-pHEMT because the Pt sunk into a deeper channel. The slope of the curve of power gain cutoff frequency (f_max) as a function of temperature was −5.76 × 10⁻² GHz/°C for a Pd/Ti/Au-gate E-pHEMT; it was −9.17 × 10⁻² GHz/°C for a Pt/Ti/Au-gate E-pHEMT. The slight variation in the dc and radio-frequency characteristics of the Pd/Ti/Au-gate E-pHEMT at temperatures from 0 to 100 °C revealed that the Pd-GaAs interface has great potential for high power transistors.     

Using Ontology and RFID Technology to Develop an Agent-Based System for Campus-Safety Management

This study proposes a distributed multi-agent system combining radio-frequency identification press technology with an ontology for special-education students in support of dynamic campus-safety management. Safety management on campus typically involves relevant supporting measures and manuals, but serious safety-related incidents continue to take place on campuses. The goal of campus security should be to identify an incident and resolve it effectively and in real time before the incident evolves into an actual crisis. Our purpose here is to improve the traceability of students involving in campus activities—that is, to identify students’ whereabouts throughout the entire school day. When an incident occurs, our system will notify the relevant parties immediately. In the present study, the agents real-time event processing increases their situational awareness and reduces the likelihood and the severity of unwanted outcomes. Basically, in this paper, we aim to demonstrate the feasibility and applicability of utilizing agent-based technologies to the special-education students.     

Influence of La substitution on the electrical properties of metal-ferroelectric (BiFeO3)-insulator (CeO2)-semiconductor nonvolatile memory structures

Metal-multiferroic (La-substituted BiFeO₃)-insulator (CeO₂)-semiconductor (MFIS) capacitors has been fabricated. The crystalline phase and amount of La³⁺ substitution at Bi-site were investigated by XRD and XPS in the postannealing temperature range from 500 to 700 °C, respectively. The microstructure and interfacial layer between CeO₂ and Si substrate were characterized by HRTEM. The memory windows as functions of insulator film thickness and DC power for La were measured. The maximum memory window is about 1.9 V under ±6 V applied voltage. The ferroelectric polarization increases with increasing substitution amount. The morphologies of La-substituted BiFeO₃ films were also studied by AFM.     

Loss behavior in space priority queue with batch Markovian arrival process — discrete-time case

This paper applies matrix-analytic approach to the examination of the loss behavior of a space priority queue. In addition to the evaluation of the long-term high-priority and low-priority packet loss probabilities, we examine the bursty nature of packet losses by means of conditional statistics with respect to critical and non-critical periods that occur in an alternating manner. The critical period corresponds to having more than a certain number of packets in the buffer; non-critical corresponds to the opposite. Hence there is a threshold buffer level that splits the state space into two. By such a state-space decomposition, two hypothesized Markov chains are devised to describe the alternating renewal process. The distributions of various absorbing times in the two hypothesized Markov chains are derived to compute the average durations of the two periods and the conditional high-priority packet loss probability encountered during a critical period. These performance measures greatly assist the space priority mechanism for determining a proper threshold. The overall complexity of computing these performance measures is of the order O(K²m₁³m₂³), where K is the buffer capacity, and m₁ and m₂ are the numbers of phases of the underlying Markovian structures for the high-priority and low-priority packet arrival processes, respectively. Thus the results obtained are computationally tractable and numerical results show that, by choosing a proper threshold, a space priority queue not only can maintain the quality of service for the high-priority traffic but also can provide the near-optimum utilization of the capacity for the low-priority traffic.     

Theory of wire addition and removal in combinational Boolean networks

Let w_t be a wire in a combinational Boolean network. There may exist a wire w_a such that when w_a is added and w_t is removed, the overall circuit functionality is unchanged. Redundancy-addition-and-removal (RAR) is an efficient technique to find such a w_a. The idea is to add a redundant alternative wire w_a to make the target wire w_t redundant. However, as long as the addition of w_a together with the removal of w_t does not change the overall functionality of the circuit, wires that are added and removed do not necessarily need to be redundant. This raises a question about the existence of alternative wires. Why can one wire replace another wire in a combinational Boolean network? In this paper, we analyze theoretically the existence of alternative wires and model it as an error-cancellation problem. The two existing rewiring techniques, the redundancy-addition-and-removal and the global flow optimization, are unified under the proposed generalized model.     

System structure and contour tracking for a hybrid motion platform

This work investigates the spatial contour tracking on a new kind of motion platform that is constructed by extending the parallel platform with a proven planar motion table. Multi-axis cross-coupled tracking control schemes were developed on the basis of this hybrid structured Stewart platform, which formed a 5-axis working machine. A framework for the functions of this system was established. Roadmap for further development that leads to a highly versatile and efficient precision motion platform was made.     

Thermal Characterization and Microstructure Change of Cobalt Oxides

A series of cobalt oxides with different oxidation states have been prepared by using a precipitation-oxidation method and a controlled reduction method (in situ thermogravimetry-temperature programmed reduction, STG-TPR). The gradual change in microstructure with different oxides is studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that high-valence cobalt oxide is hexagonal with an elongated shape, Co₃O₄ is spinel with hollow spheroidal shape and CoO is a face-centered cubic structure, respectively.     

Observation of explosive spectral behaviors in proton-enhanced high-Q inductors and their explanations

The verified success of proton-beam treatment in both device isolation and inductor Q-improvement on Si substrates is now enticing some big chipmakers into realizing a VLSI back-end facility: the particle-beam stand (PBS). The PBS can potentially end the traditionally laborious mixed-mode product development cycle and eventually become the general system-on-a-chip (SOC) integration platform. However, the observed Q-improvement might in fact fall short of what it should be. Namely, if substrate resistivity is the sole dominant factor deciding the ultimate inductor Q value, then the proton-achieved resistivity does not bring forth the anticipated ideal Q value. Furthermore, there are several puzzles in the observed inductance spectral behaviors. Thus, there is an explosive rise of inductance near certain frequencies in some cases but not in others, and the inductor size effect alters the frequency at which these inductance rises occur. Such difficulties outwit the existing understanding of the microstrip inductors. A new theory is briefly presented here to unravel the cause of such incomplete Q-improvement and hopefully to resolve all related puzzles. It includes identifying the inductor-substrate coupling effect as a result of the proton bombardment, using a special dipole-dominated expansion of the inductor system equations, and further applying the notion of electromagnetic mass of the electron. With such theoretical insight, ideal high-Q passives may be just a few steps away using the so-called "dipole engineering" approach on PBS.     

Using metal/organic junction engineering to prepare an efficient organic base-modulation triode and its inverter

In this study, we investigated the influence of a buffer layer of molybdic oxide (MoO₃) at the metal/organic junction on the behavior of organic base-modulation triodes. The performance of devices featuring MoO₃/Al as the emitter electrode was enhanced relative to that of corresponding devices with Au and Ag, presumably because of the reduced in the contact barrier and the prevention of metal diffusion into the organic layer. The device exhibited an output current of ?16.1 μA at V_B = ?5 V and a current ON/OFF ratio of 10³. Using this architecture, we constructed resistance–load inverters that exhibited a calculated gain of 6.