Formation of a step-free InAs quantum well selectively grown on a GaAs (111)B substrate

We investigated the possibility of forming a step-free quantum well structure. A step-free InAs monolayer was grown on a selectively grown mesa by controlling surface phases with in-situ monitoring of surface photo-absorption. We selectively grew a GaAs buffer at 800°C and cooled the sample keeping the (2×2)-like As stabilized surface. Atomic force microscopy (AFM) observation demonstrated that fully step-free surfaces were formed on the 8 μm wide mesa. Then, a monolayer-thick InAs was formed on this step-free surface and this InAs layer was capped by GaAs under the (2×2)-like condition. The quantum level of the step-free InAs layer was evaluated by spatially resolved photoluminescence (μPL) measurement. Uniform PL intensity and the lack of a double layer peak indicated the formation of a step-free InAs quantum well, which was in good agreement with AFM observation.     

A low-resistance self-aligned T-shaped gate for high-performancesub-0.1-μm CMOS

This paper describes the high performance of T-shaped-gate CMOS devices with effective channel lengths in the sub-0.1-μm region. These devices were fabricated by using selective W growth, which allows low-resistance gates smaller than 0.1 μm to be made without requiring fine lithography alignment. We used counter-doping to scale down the threshold voltage while still maintaining acceptable short-channel effects. This approach allowed us to make ring oscillators with a gate-delay time as short as 21 ps at 2 V with a gate length of 0.15 μm. Furthermore, we experimentally show that the high circuit speed of a sub-0.1-μm gate length CMOS device is mainly due to the PMOS device performance, especially in terms of its drivability     

Device design with automatic simulation system for basic CCDcharacteristics

A simulation system has been developed to automatically analyze basic electrical characteristics of a charge-coupled device (CCD) image sensor from a process simulation result. This system shortened the simulation period to approximately 1/10 by getting rid of complicated repetitious procedures. A high-performance new cell technology has been developed successfully with improving impurity distribution in shorter development time by using this system. This technology has been realized as a CCD cell pixel with CCD charge quantity of 1.8 times, effective transfer efficiency of over 99%, no image lag for driving read-out pulse voltage in comparison with conventional technology. A 1/4-in 330 K square pixel progressive-scan CCD was fabricated with this technology. These results are described to demonstrate the effectiveness of the automatic simulation system     

Electrochemically induced asymmetrical etching in InAlAs/InGaAs heterostructures for MODFET gate-groove fabrication

We have achieved a self-controlled asymmetrical etching in metalorganic chemical vapor deposition-grown InAlAs/InGaAs heterostructures, which can be suitable for fabricating modulation-doped field-effect transistors (MODFETs) with gate-groove profiles for improved performance. The technology is based on electrochemical etching phenomena, which can be effectively controlled by using different surface metals for ohmic electrodes. When surface metals of Pt and Ni are deposited on the source and the drain, respectively, the higher electrode potential of Pt results in slower etching on the source side than on the drain side. Thus, asymmetry of gate grooves can be formed by wet-chemical etching with citric-acid-based etchant. This represents a new possibility to conduct “recess engineering” for InAlAs/InGaAs MODFETs.     

A 950-MHz rectifier circuit for sensor network tags with 10-m distance

This paper presents a 950-MHz wireless power transmission system and a high-sensitivity rectifier circuit for ubiquitous sensor network tags. The wireless power transmission offers a battery-life-free sensor tag by recharging the output power of a base station into a secondary battery implemented with the tag. For realizing the system, a high-sensitivity rectifier with dynamic gate-drain biasing has been developed in a 0.3-/spl mu/m CMOS process. The measurement results show that the proposed rectifier can recharge a 1.2-V secondary battery over -14-dBm input RF power at a power conversion efficiency of 1.2%. In the proposed wireless system, this sensitivity corresponds to 10-m distance communication at 4-W output power from a base station.     

Mechanism of O2-anneal induced Vfb shifts of Ru gated stacks

A systematic study of the flat-band voltage (V_fb) shift of Ru gated metal-oxide-semiconductor (MOS) capacitors subjected to thermal treatment in O₂ has been performed. The dependence of the V_fb shift on the thickness of Ru, anneal temperature and time is studied. The V_fb shift is ascribed to the shift of metal gates’ work function (WF), and is not significantly dependent on the type of dielectric (HfO₂ or SiO₂). From time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurement, it was found that after thermal treatment in ¹⁸O₂, ¹⁸O penetrated through Ru and was incorporated in the Ru/dielectric interface region. We believe that the formation of the thin interfacial RuO_x layer is responsible for the V_fb shift.     

A QoS-aware routing mechanism for multi-channel multi-interface ad-hoc networks

To accommodate real-time multimedia application while satisfying application QoS requirements in a wireless ad-hoc network, we need QoS control mechanisms. In this paper, we propose a new routing mechanism to support real-time multimedia communication by efficiently utilize the limited wireless network capacity. Our mechanism considers a wireless ad-hoc network composed of nodes equipped with multiple network interfaces to each of which a different wireless channel can be assigned. By embedding information about channel usage in control messages of OLSRv2, each node obtains a view of topology and bandwidth information of the whole network. Based on the obtained information, a source node determines a logical path with the maximum available bandwidth to satisfy application QoS requirements. Through simulation experiments, we confirmed that our proposal effectively routed multimedia packets over a logical path avoiding congested links. As a result, the load on a network is well distributed and the network can accommodate more sessions than QOLSR. We also conducted practical experiments using wireless ad-hoc relay nodes with four network interfaces and verified the practicality of our proposal.     

Gold Nanoparticle and Gold Nanorod Embedded PEDOT:PSS Thin Films as Organic Thermoelectric Materials

We report the thermoelectric properties of organic–inorganic hybrid thin films composed of conductive polymer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and inorganic gold nanomaterials. Two kinds of material with different shapes, namely rod-shaped gold nanorods (AuNRs) and spherical gold nanoparticles (AuNPs), were used in this study. The PEDOT:PSS/AuNR hybrid films showed an enhancement in electrical conductivity (σ ≈ 2000 S cm^?1) and concurrently a decrease in the Seebeck coefficient (S ≈ 12 μV K^?1) with increase in the AuNR concentration. This behavior indicates the presence of the hybrid effect of AuNR on the thermoelectric properties. From scanning electron microscopy (SEM) observation of the highly concentrated PEDOT:PSS/AuNR hybrid films, the formation of a percolated structure of AuNRs was confirmed, which probably contributed to the large enhancement in σ. For the highly concentrated PEDOT:PSS/AuNP films, a dense distribution of AuNPs in the film was also observed, but this did not lead to a major change in the σ value, probably due to the less conductive connections between NPs. This suggests that one-dimensional particles with larger aspect ratio (rods and wires) are favorable nanocomponents for development of highly conductive hybrid materials.     

氟伐他汀对2型糖尿病合并高胆固醇血症患者的抗氧化作用

目的调查氟伐他汀对2型糖尿病合并高胆固醇血症患者体内氧化压力的影响以及与降脂作用的相关性。方法糖尿病合并高脂血症患者41例,男21例,女20例,平均年龄（56．7±6．0）岁,均在日本弘前大学附属医院收集。每晚服用20mg氟伐他汀,于用药前及用药后4、8、12周分别测定血浆中低密度脂蛋白（LDL）,LDL size、LHPO、TBARS的动态变化。结果血浆LHPO,TBARS、LDL—C在用药的第8周（分别为19．4±8．1 vs43.3±13．1nmol／mg LDLpm;5．33±0．97vs8．83±1．11nmol／mL;125±9vs157±12mg／dL,P〈0．05）和12周（分别为14．4±5．1vs43．3±13．1nmol／mg LDLpro;2．3±0．3vs8．83±1．11nmol／mL;131±5vs157±12mg／dL,P〈0．05）明显降低,LDL size无统计学差异。结论氟伐他汀能够显著降低患者血中的LHPO、TBARS、LDL,表明对2型糖尿病合并高脂血症患者有抗氧化作用．且与其抗血脂的作用相关．     

Realization of an extremely low reflectance surface based on InP porous nanostructures for application to photoelectrochemical solar cells

Extremely low reflectance was obtained from InP porous nanostructures in UV, visible, and near-infrared ranges. Porous samples were electrochemically prepared on which 130-nm-diameter nanopores were formed in a straight, vertical direction and were laterally separated by 50-nm-thick InP nanowalls. The reflectance strongly depended on the surface morphology. The lowest reflectance of 0.1% in the visible light range was obtained after the irregular top layer had been completely removed. Superior photoelectrochemical properties were obtained on the InP porous structures due to two unique features: the large surface area inside pores, and the large photon absorption enhanced on the low reflectance surface.