Unified Degradation Model in Low Gate Voltage Range During Hot-Carrier Stressing of p-MOS Transistors

Hot carrier effects of p MOSFETs with different oxide thicknesses are studied in low gate voltage range.All electrical parameters follow a power law relationship with stress time,but degradation slope is dependent on gate voltage.For the devices with thicker oxides,saturated drain current degradation has a close relationship with the product of gate current and electron fluence.For small dimensional devices,saturated drain current degradation has a close relationship with the electron fluence.This degradation model is valid for p MOSFETs with 0 25μm channel length and different gate oxide thicknesses.

Degradation of P-MOSFETs Under Off-State Stress

The hot carrier effects under off- state stress m ode( Vgs=0 ,Vds<0 ) have been investigated on9nm P- MOSFETs with channel length varying from1.0 2 5 μm to0 .5 2 5 μm.Both on- and off- state currents are discussed. It is found that the off- state leakage current decreases after a higher voltage stressing,which is induced by the charge injection occurred close to the drain junction.However,the leakage current increases after a lower voltage stressing because of the newly generated interface traps.It is also found that the on state saturation current and threshold voltage degrade significantly with the stress tim e,which we believe is due to the charges injected near the gate- drain overlapping region and/ or the stress- induced interface trap generation.The degradation of Idsatcan be ex- pressed as a function of the product of the gate current( Ig) and the num ber of charges injected into the gate oxide ( Qinj) in a simple power law.Finally,a lifetime prediction model based on the degradation of Idsatis proposed.

Strained-Si pMOSFETs on Very Thin Virtual SiGe Substrates

Strained-Si pMOSFETs on very thin relaxed virtua l SiGe substrates are presented.The 240nm relaxed virtual Si 0.8 Ge 0.2 layer on 100nm low-temperature Si(LT-Si) is grown on Si(100) substrates by molecular beam epitaxy.LT-Si buffer layer is used to release stress of the SiGe layer so as to make it relaxed.DCXRD,AFM,and TEM measurements indicate that the strain relaxed degree of SiGe layer is 85%,RMS roughness is 1.02nm,and threading dislocation density is at most 107cm -2 .At room temperature,a maximum hole mobility of strained-Si pMOSFET is 140cm2/(V·s).Device performance is comparable to that of devices achieved on several microns thick relaxed virtual SiGe substrates.

Optical and Electrical Properties of GaN:Mg Grown by MOCVD

Mg-doped GaN layers prepared by metalorganic chemical vapor deposition were annealed at temperatures between 550 and 950℃. Room temperature （RT） Hall and photoluminescence （PL） spectroscopy measurements were performed on the as-grown and annealed samples. After annealing at 850℃, a high hole concentration of 8 × 10^17 cm^-3 and a resistivity of 0. 8lΩ·cm are obtained. Two dominant defect-related PL emission bands in GaN.. Mg are investigated; the blue band is centered at 2. 8eV （BL） and the ultraviolet emission band is around 3.27eV （UVL）. The relative intensity of BL to UVL increases after annealing at 550℃, but decreases when the annealing temperature is raised from 650 to 850℃, and finally increases sharply when the annealing temperature is raised to 950~C. The hole concentration increases with increased Mg doping, and decreases for higher Mg doping concentrations. These results indicate that the difficulties in achieving high hole concentration of 10^18cm^-3 appear to be related not only to hydrogen passivation, but also to self-compensation.

Geostrophic meridional transport in tropical Northwest Pacific based on Argo profiles

Absolute geostrophic currents in the North Pacific Ocean were calculated using P-vector method from newly gridded Argo profiling float data collected during 2004-2009. The meridional volume transport of geostrophic currents differed significantly from the classical Sverdrup balance, with differences of 10×106 -20×106 m3 /s in the interior tropical Northwest Pacific Ocean. Analyses showed that errors of wind stress estimation could not explain all of the differences. The largest differences were found in the areas immediately north and south of the bifurcation latitude of the North Equatorial Current west of the dateline, and in the recirculation area of the Kuroshio and its extension, where nonlinear eddy activities were robust. Comparison of the geostrophic meridional transport and the wind-driven Sverdrup meridional transport in a high-resolution OFES simulation showed that nonlinear effects of the ocean circulation were the most likely reason for the differences. It is therefore suggested that the linear, steady wind-driven dynamics of the Sverdrup theory cannot completely explain the meridional transport of the interior circulation of the tropical Northwest Pacific Ocean.

Aerodynamic Effects on TLP Type Wind Turbines and Predictions of the Electricity They Generate

This research proposes a new offshore wind energy generation system that uses a tension leg platform (TLP) and describes experiments performed on a TLP type wind turbine in both waves and wind. The following conclusions can be made from the results of this research. 1) In the case of coexisting wave-wind fields, the wind effect stabilizes the pitch motion. 2) The wind effect decreases vibration of the mooring lines when waves and wind coexist. In particular, the springing (2nd or 3rd order force) also decreases in this field. 3) It can be estimated that the reduction in the rate of generation of electrical power can be up to about 6% as a result of the heel angle. In addition, the annual amount of electricity generated was estimated along with the utilization factor based on the experimental results.

Scour effect on a sea-crossing bridge under combined action of service and extreme seismic loads

Foundation scour is an important cause for structural failure of sea-crossing bridges. Usually, the sea-crossing bridges operate under the harsh natural environment in which service wind, wave and vehicle loads are stronger and extreme loads such as earthquake, hurricane, and ship collision, are more frequent. As a result of the foundation scour,the dynamic behavior of bridge under different combined action of service and extreme loads may be further escalated.In particular, this work has investigated the scour effect on a sea-crossing bridge under service wind, wave and vehicle loads as well as extreme seismic loads. The dynamic coupled earthquake-wind-wave-vehicle-bridge(EWWVB) system is established by considering the interactions within the system, and the p-y curve method is used to calculate the loaddisplacement relation of the pile and soil under various levels of foundation scour. After that, a case study has been performed on a cable-stayed bridge with foundation scour. The results indicate that the dynamic characteristics of bridge structure will change after considering bridge scour, and the dynamic responses of bridge and vehicle will be affected to different degrees under service and seismic loads considering bridge scour.

Electrical transport and photoresponse properties of single-crystalline p-type Cd_3As_2 nanowires

Cd3As2 is an important II-V group semiconductor with excellent electrical and optoelectronic properties. In this work, we report the large scale growth of single-crystalline Cd3As2 nanowires via a simple chemical vapor deposition method. Single nanowire field-effect transistors were fabricated with the as-grown Cd3As2 nanowires, which exhibited a high lon/loff of 104 with a hole mobility of 6.02 cm2V-1s-1. Photoresponse properties of the Cd3As2 nanowires were also investigated by illuminating the nanowires with white light by varying intensities. Besides, flexible photodetectors were also fabricated on flexible PET substrate, showing excellent mechanical stablility and flexible electro-optical properties under various bending states and bending cycles. Our results indicate that Cd3As2 nanowires can be the basic material of next generation electronic and ootoelectronic devices.

A fast SOI-based variable optical attenuator with a p-i-n structure with low polarization dependent loss

According to the plasma dispersion effect of silicon(Si),a silicon-on-insulator(SOI) based variable optical attenuator(VOA) with p-i-n lateral diode structure is demonstrated in this paper.A wire rib waveguide with sub-micrometer cross section is adopted.The device is only about 2 mm long.The power consumption of the VOA is 76.3 mW(0.67 V,113.9 mA),and due to the carrier absorption,the polarization dependent loss(PDL) is 0.1dB at 20dB attenuation.The raise time of the VOA is 34.5 ns,the fall time is 37 ns,and the response time is 71.5 ns.

基于有限杆单元法的陡坡段桥梁基桩受力分析

为了对山区高陡边坡桥梁桩基进行合理分析,提出了一种改进有限杆单元法。首先,对通用杆系有限单元法的单元刚度矩阵进行修正,以综合考虑"P-Δ"效应及桩土相互作用对桩身内力和位移的影响。在此基础上,根据陡坡段基桩不同特征段的受力变形特点,将基桩划分为自由段、受荷段和嵌固段,并对桩身荷载及边界条件进行处理,建立了适用于高陡边坡桥梁桩基内力位移分析的改进有限杆单元法,并以MATLAB为平台编制了相应的计算程序。最后,结合某工程实例,重点分析了剩余下滑力大小、桩顶荷载形式等因素对基桩内力及位移的影响。研究结果表明:理论计算值与室内模型试验的实测结果吻合较好,最大相对误差在10%以内,表明该方法正确、可行;高陡边坡条件下桥梁基桩桩顶荷载对桩身内力有显著影响,"P-Δ"效应明显,在实际工程中应对其予以考虑。

Nonlinear analysis of pile groups subjected to combined lateral and torsional loading

An empirical approach has been developed to analyze the nonlinear response of a pile group with arbitrarily distributed piles subjected to combined lateral and torsional loading.In this approach,the concept of instantaneous twist center is applied to analyze the displacement relationship of pile heads and establish the static equilibrium equations of the pile cap.The horizontal interaction among the individual piles is considered through the generalized p-multiplier.The coupling effect of lateral resistance on the torsional resistance of each pile is quantified using an empirical factorβ;the lateral and torsional nonlinear responses of individual piles are modeled by p-y andτ-θcurves,respectively.The proposed approach not only captures the most significant aspect of the group effect and coupling effect in a pile group subjected to combined lateral and torsional loading,but also automatically updates p-multipliers of individual piles based on pile cap displacements.The proposed approach was verified using results of model tests on pile groups subjected to lateral loading,torsional loading,and combined lateral and torsional loading,separately.In general,the pile cap response and the transfer of applied loads in the pile groups agree well with the test results.

Structural,electronic,and thermoelectric properties of La_2CuBiS_5

The basic physical properties of La_2CuBiS_5 are studied by the first-principle calculations and the semiclassical Boltzmann theory.Charge density difference calculations show that electrons accumulate between Bi-S atoms,indicating considerable covalent bonding of Bi and S atoms.A similar charge density difference indicates that the Cu-S bonds also exhibit covalent character.The calculated minimum thermal conductivity of La_2CuBiS_5 is low,which is conducive to its use as a thermoelectric material.Owing to a bipolar effect,induced by thermal excitation,the material＇s Seebeck coefficient decreases sharply at T = 800 K.For the n-type and p-type doping conditions,the largest values of S^2σ/τ were calculated as-1.71×10^（11） and 1.837×10^（11） W K^（-2）ms^（-1）,respectively.The combination of a large dispersion and a high band degeneracy along the Γ-Y direction in the band structure simultaneously induces the highest S_y value and a high σ/τ_y value.Thus,the thermoelectric performance of La_2CuBiS_5 is anisotropic and most favorable along the y direction.

Electrocaloric Effect of P(VDF-TrFE)/SrTiO_3 Bilayer Thin Films

A phenomenological thermodynamic theory is applied to investigate the effect of misfit strgin and electric field on the electrocaloric effect of P（VDF-TrFN）/SrTiO3 bilayer thin films. Theoretical results indicate that the low electric field results in the decrease of the average polarization with the increase of the relative thickness of SrTi03 layer, and the high electric field has an opposite effect on it. Moreover, the electroealoric effect strongly depends on the electric field. The low electric field and the small field change can lead to a maximum of the electrocaloric effect, meanwhile the high electric field or the large field change results in the opposite trend.