Spin-Current Shot Noise in Mesoscopic Conductors

In this paper, we present a method to investigate the spin-current shot noise in mesoscopic conductors, by using scattering matrix theory and Green's function technique. We first derive a general expression for the spin-current noise at zero-frequency limit, and extract the shot-noise component by discussing it at zero-temperature limit. The expression indicates that the spin-current shot noise in one lead is caused by the transmissions to the spin-resolved states in this lead and the interferences of these transmissions. As an application, we simulate the spin-current shot noise in a spin transistor, and discuss its dependence on the device parameters and the bias voltages applied to the transistor. The knowledge we gain from this study will help researchers to evaluate the spin-current shot noise in the future spintronic devices.Comment: 6 figure

Fabrication and Properties of Self-aligned Double-Gate Poly-Si TFT

In this paper, a novel self-aligned double-gate (SLambdaDG) TFT technology is proposed and experimentally demonstrated for the first time. The self-alignment between the top- and bottom-gate is realized by a non-critical chemical-mechanical polishing (CMP) step. An ultra-thin channel and a thick source/drain that allow better device performance and lower source/drain resistance, are also automatically achieved. N-channel polysilicon TFTs are fabricated with maximum fabrication temperature below 600 degreesC. The fabricated SABG-TFT exhibits symmetrical bi-directional transfer characteristics when the polarity of source/drain bias is interchanged. Moreover, the on-current under double-gate operation is more than 4 times that under single-gate operation, and more than 2 times the sum of that under top-gate and bottom-gate operation respectively. Furthermore, the effective mobility is also increased from 53 cm(-2)/V-s of single-gate mode to 87 cm(-2)/V-s of double-gate mode.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000174745900343&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Engineering, Electrical & ElectronicMaterials Science, MultidisciplinaryPhysics, AppliedPhysics, Condensed MatterCPCI-S(ISTP)

A Viable Self-aligned Bottom-Gate MOSFET Technology for High Density and Low Voltage SRAM

This paper reports the implementation of the bottomgate MOSFET which possesses the following fully-selfaligned structural features: 1) self-aligned source/drain to bottom-gate; 2) self-aligned thick source/drain to thin channel; 3) self-aligned and mask-free lightly-dopeddrain (LDD). The complete self-alignment is realized by combining a conventional ion implantation and a subsequent CMP step. The process is applied to the poly-Si film, which is crystallized from an a-Si film deposited by LPCVD using Metal-Induced Uni-lateral Crystallization (MIUC) technique and is grain-enhanced further in a high temperature annealing step. Deep submicron Fully Self-Aligned Bottom-Gate (FSABG) PMOS transistors with channel length less than 0.5 ??m are fabricated. The measured performance parameters include threshold voltage of -0.43V, subthreshold swing of 113 mV/dec, effective hole mobility of 147 cm2/V-s, off-current of 0.17 pA/??m and on-off current ration of 7.1??108.EI

Impact of Thickness and Deposition Temperature of Gate Dielectric on Valence Bands in Silicon Nanowires

The strain distribution and strained valence band structure in silicon nanowire with varied thicknesses and deposition temperatures of gate dielectric are discussed in detail in this work. Our calculation indicates that valence subbands are dependent on the structure and process parameters. Strain has little effects in (001) orientation. But in Si (110) nanowire, the valence subbands shift upper and warp remarkably as the gate dielectric becomes thicker. Taking thermal residual strain into consideration, the strained valence subbands go to higher energy positions compared to NW without the residual strain. The different deposition temperature by a certain process slightly influences the valence bands. Strain effects on densities of states and effective masses are also investigated.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000277103100059&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Computer Science, Theory & MethodsEngineering, Electrical & ElectronicEICPCI-S(ISTP)

Divergent historical GPP trends among state-of-the-art multi-model simulations and satellite-based products

International audienceUnderstanding historical changes in gross primary productivity (GPP) is essential for better predicting the future global carbon cycle. However, the historical trends of terrestrial GPP, due to the CO2 fertilization effect, climate, and land-use change, remain largely uncertain. Using long-term satellite-based near-infrared radiance of vegetation (NIRv), a proxy for GPP, and multiple GPP datasets derived from satellite-based products, dynamic global vegetation model (DGVM) simulations, and an upscaled product from eddy covariance (EC) measurements, here we comprehensively investigated their trends and analyzed the causes for any discrepancies during 1982-2015. Although spatial patterns of climatological annual GPP from all products and NIRv are highly correlated (r>0.84), the spatial correlation coefficients of trends between DGVM GPP and NIRv significantly decreased (with the ensemble mean of rCombining double low line0.49) and even the spatial correlation coefficients of trends between other GPP products and NIRv became negative. By separating the global land into the tropics plus extratropical Southern Hemisphere (Trop+SH) and extratropical Northern Hemisphere (NH), we found that, during 1982-2015, simulated GPP from most of the models showed a stronger increasing trend over Trop+SH than NH. In contrast, the satellite-based GPP products indicated a substantial increase over NH. Mechanistically, model sensitivity experiments indicated that the increase of annual global total GPP was dominated by the CO2 fertilization effect (83.9g% contribution), however, with the largest uncertainty in magnitude in individual simulations among the three drivers of CO2 fertilization, climate, and land-use change. Interestingly, the spatial distribution of inter-model spreads of GPP trends resulted mainly from climate and land-use change rather than CO2 fertilization effect. After 2000, trends from satellite-based GPP products were different from the full time series, suggesting weakened rising trends over NH and even significantly decreasing trends over Trop+SH, while the trends from DGVMs and NIRv kept increasing. The inconsistencies of GPP trends are very likely caused by the contrasting performance between satellite-derived and DGVM simulated vegetation structure parameter (leaf area index, LAI). Therefore, the uncertainty in satellite-based GPP products induced by highly uncertain LAI data in the tropics undermines their roles in assessing the performance of DGVM simulations and understanding the changes of global carbon sinks. The higher consistency between DGVM GPP and NIRv suggests that the trends from a DGVM ensemble might even have better performance than satellite-based GPP products