Electron-beam-induced-current investigation of GaN/AlGaN/Si heterostructures using scanning transmission electron microscopy

An electron-beam-induced-current technique has been applied to scanning transmission electron microscopy to characterize GaN/AlGaN/n-Si heterostructures. The structure was formed by metalorganic vapor phase epitaxy using AlGaN as an intermediate layer. Two samples with nominal intermediate layer thicknesses of 60 and 120 nm were studied. It was found that there is a junction in the n-type Si region underneath the nitride/Si interface irrespective of the intermediate layer thickness, whereas induced current occurred neither in the nitride region nor at the nitride/Si interface. The junction formed was found to be undulated. The sample with the thin intermediate layer had undulations of a shorter periodicity than that with the thick intermediate layer. The formation of the junction is attributed to the diffusion of Al during the nitride growth.     

An Analysis of Two Liquid-State Adaptive Feedback Experiments

Adaptive feedback experiments, which provide an engineering oriented approach to optimizing a desired target in a molecular process, have been extensively developed over the past decade. Efforts to extract the control mechanisms that underlie the observed control have, however, only recently begun in earnest. We describe the results of the analyses of two liquid state adaptive feedback experiments, showing that the resultant control takes little advantage of coherent quantum effects.     

An 800-MHz embedded DRAM with a concurrent refresh mode

An 800-MHz embedded DRAM macro employs a memory cell utilizing a device from the 90-nm high-performance technology menu; a 2.2-nm gate oxide 1.5 V IO device. A concurrent refresh mode is designed to improve the memory utilization to over 99% for a 64 /spl mu/s data retention time. A concurrent refresh scheduler utilizes up-count and down-count registers to identify at least one array to be refreshed at every clock cycle, emulating a classical distributed refresh mode. A command multiplier employs low frequency phased clock signals to generate the clock, commands, and addresses at rates up to 4/spl times/ that of the tester frequency. The macro integrates masked redundancy allocation logic during at speed multibank test. The hardware results show a 312-MHz random access frequency and 800-MHz multibank frequency at 1.2 V, respectively.     

冲击电压下残余电荷对沿面放电发展的影响

固体绝缘的表面是高压电力设备绝缘的最薄弱环节,很多绝缘事故都是由沿面放电造成的。发生放电后,电荷会在绝缘表面积聚,会很大程度上影响下一次放电的产生与发展。为此,通过观测在极性交替变化的冲击电压作用下沿同轴圆柱形聚对苯二甲酸乙二醇酯（PET）绝缘表面放电的发展以及测量放电后表面残余电荷电位的分布,来研究残余电荷对沿面放电的影响。研究表明,在改变冲击电压的极性后,由于反极性残余电荷的影响,放电会被促进,放电通道会沿着前一次放电的通道向前发展,并且会比前一次放电距离略长,放电的强度会增强,放电的发展速度也会加快。在沿着放电通道方向,表面电荷电位梯度可以明显分为两部分：在放电头部的20mm区域,电位梯度较大,为流注放电;而在后面的主干部,电位梯度平缓,为先导放电。     

Experimental study of collaborater in human–machine system

A human intervention is essential for human–machine system and human operator’s skill affects deeply achievement of the control purpose. By keeping the human operation easy, an operator can concentrate on more advanced decision so that the operation performance is improved. In this paper, a new concept of human-oriented compensator is proposed for improving the human–machine system, which is named “collaborater”. The design approach exists in human dynamics, and 2DOF structure is introduced. The simulation results confirm that the time and frequency responses are improved. Moreover the experimental results also confirm the similar effect of proposed method.     

A Method of Study of Radioactive Tracer Kinetics

This paper presents an approach to the problem of estimating the number of exponential functions and the pertinent parameters in the output of a radioactive tracer kinetic process. In particular, application of a criterion called an information theoretical criterion (AIC) for the estimation of the number of exponential functions is proposed; AIC was introduced by Akaike for the estimation of the order of linear dynamical systems and has been successfully applied for statistical model identification in a wide range of fields. Also, the maximum likelihood method was applied in order to evaluate AIC and to estimate decay constants and coefficients.     

Application of electron holography to the determination of contact potential difference in an AlGaN/AlN/Si heterostructure

Electron holography was applied to determine the contact potential differences in an AlGaN/AlN/Si heterostructure formed by metallorganic vapor phase epitaxy. Since mean inner potentials are generally different for different materials, their values before and after forming the junction were evaluated first, then the contact potential difference was obtained by subtracting the difference of the mean inner potentials before forming the junction from the corresponding difference after forming the junction. The contact potential differences thus obtained were consistent with a reported asymmetric nonlinear behavior in the current-voltage characteristics measured for a similar heterojunction diode.     

Model-based fault detection and isolation in steer-by-wire vehicle using sliding mode observer

Steer-by-Wire system (SbW), in which the conventional mechanical linkages between the steering wheel and the front wheel are removed, is suited to active steering control, improving vehicle stability, dynamics and maneuverability. And SbW is implemented to autonomous steering control to assist the driver. However, the SbW vehicle contains unsolved important problems about fault tolerant function. For example, it is the detection of sensor fault and multiplicative fault simultaneously. Fault detection and isolation (FDI) is essential in fault-tolerant problems, and conventional FDI for SbW was based on Kalman filter. But this method has weak robustness and cannot detect sensor fault and multiplicative fault simultaneously. We propose a novel model-based fault detection and isolation method using sliding mode observer in the SbW vehicle, which contains measurement of sensor fault and multiplicative fault. The effectiveness of the proposed method is verified by simulations. This paper was recommended for publication in revised form by Associate Editor Kyoungsu Yi Jae-Sung Im was born in Busan, Korea in 1978. He received his B.S. and M.S. degrees in Mechanical Engineering from Pukyong National University, Korea, in 2003 and 2005, respectively. He then received his Ph.D. degree from Kumamoto University, Japan, in 2009. His interests are in vehicle dynamics, robust control, fault detection and isolation, and man-machine interface. Fuminori Ozaki received the B.S. and M.S. degrees from the Department of Computer Science, Kumamoto University, Japan, in 1998 and 2000. In 2000, he joined OMRON Corporation, Kyoto, Japan, where he developed semiconductor manufacturing equipment. His current interests include EPS control and KANSEI engineering. Tae-Kyeong Yue received the B.S. and M.S. degrees from Pukyong National University, Korea, in 1998 and 2000, respectively. He received the Ph.D. degree from Kumamoto University, Kumamoto, Japan in 2003. He is working in the Korea Ocean Research and Development Institute (KORDI), Korea. His interests are fault detection and isolation, decentralized control and control of deep-sea mining system. Shigeyasu Kawaji received his Master of Engineering in Electrical Engineering and Doctor of Engineering in Control Engineering from Kumamoto University and Tokyo Institute of Technology, Japan, in 1969 and 1980, respectively. He joined the Department of Electronic Engineering of Kumamoto University, Japan, where he is presently as a full professor. He is the Director of System Integration Laboratory. He is presently the President of Advanced Health Laboratory Ltd. His current research interest includes robust control, intelligent control mechatronics and robotics, fusion of medicine and engineering, and automotive mechatronic systems.     

Adsorption and aggregation of Fe(III)-hydroxy complexes during the photodegradation of phenol using the iron-added-TiO(2) combined system

The behavior of Fe(III) aquacomplexes in TiO(2) suspensions in the degradation of phenol has been investigated. The most active Fe(OH)(2+) species adsorbed on the surface of TiO(2) retards the conversion of Fe(OH)(2+) into oligomers and therefore increases the percentage of Fe(OH)(2+) with irradiation time, with a consequent enhancement in the catalytic cycle of Fe(III)/Fe(II) and excited charge traps by Fe(III) in the iron-TiO(2) system. The influence of iron addition on TiO(2) was obtained when the regeneration of [Fe(OH)(2+)] remained continuous with irradiation time. In an optimum TiO(2) suspension (0.5g/L) with the addition of 0.1mM Fe(III), the measured k(obs) values for phenol degradation were enhanced for the higher adsorption of Fe(OH)(2+) on the reactive surface of TiO(2) at a specified irradiation time.     

Calculation of Direct Tunneling Current through Ultra-Thin Gate Oxides Using Complex Band Models For SiO2

We report the calculation of gate leakage currents through the ultra-thin gate oxides (2.6–3.4 nm) in MOSFETs. We simulate J-V characteristics for the direct tunneling of valence electrons and inversion layer holes, which are measured using a charge separation technique. A two-band model is employed to express the complex band structure of the gate oxide, and its validity is discussed by calculating the complex band structure of -cristobalite based on the second nearest neighbor sp ³ s* tight-binding scheme.