By applying nonequilibrium Green’s functions (NEGF) in combination with the density functional theory (DFT), we investigate the electronic transport properties of gated phenalenyl molecular devices with two different...By applying nonequilibrium Green’s functions (NEGF) in combination with the density functional theory (DFT), we investigate the electronic transport properties of gated phenalenyl molecular devices with two different contact geometries. The calculated results show that electronic transport properties of the two different devices can be modulated by external transverse gates. When the molecule contacts the Au electrodes through two second-nearest sites, the current-voltage (<em>I</em>-<em>V</em>) characteristic curves are symmetric and suppressed by the gate electrodes. However, a rectifying behavior will occur when the electrodes connect the molecule on both sides, one second-nearest site and one third-nearest site, respectively. Mechanisms for such phenomena are proposed and these findings suggest a new opportunity for developing molecular devices.展开更多
The electrical characteristics of a double-gate armchair silicene nanoribbon field-effect-transistor （DG ASiNR FET） are thoroughly investigated by using a ballistic quantum transport model based on non-equilibrium G...The electrical characteristics of a double-gate armchair silicene nanoribbon field-effect-transistor （DG ASiNR FET） are thoroughly investigated by using a ballistic quantum transport model based on non-equilibrium Green＇s function （NEGF） approach self-consistently coupled with a three-dimensional （3D） Poisson equation. We evaluate the influence of variation in uniaxial tensile strain, ribbon temperature and oxide thickness on the on-off current ratio, subthreshold swing, transconductance and the delay time of a 12-nm-length ultranarrow ASiNR FET. A novel two-parameter strain mag- nitude and temperature-dependent model is presented for designing an optimized device possessing balanced amelioration of all the electrical parameters. We demonstrate that employing HfO2 as the gate insulator can be a favorable choice and simultaneous use of it with proper combination of temperature and strain magnitude can achieve better device performance. Furthermore, a general model power （GMP） is derived which explicitly provides the electron effective mass as a function of the bandgap of a hydrogen passivated ASiNR under strain.展开更多
In this paper the influences of the metal-gate and high-k/SiO 2 /Si stacked structure on the metal-oxide-semiconductor field-effect transistor（MOSFET） are investigated.The flat-band voltage is revised by considering...In this paper the influences of the metal-gate and high-k/SiO 2 /Si stacked structure on the metal-oxide-semiconductor field-effect transistor（MOSFET） are investigated.The flat-band voltage is revised by considering the influences of stacked structure and metal-semiconductor work function fluctuation.The two-dimensional Poisson＇s equation of potential distribution is presented.A threshold voltage analytical model for metal-gate/high-k/SiO 2 /Si stacked MOSFETs is developed by solving these Poisson＇s equations using the boundary conditions.The model is verified by a two-dimensional device simulator,which provides the basic design guidance for metal-gate/high-k/SiO 2 /Si stacked MOSFETs.展开更多
Look Up Tables(LUTs) are the key components of Field-Programmable Gate Arrays(FPGAs)Many LUT architectures have been studied; nevertheless, it is difficult to quantificationally evaLUT based architecture. Traditionall...Look Up Tables(LUTs) are the key components of Field-Programmable Gate Arrays(FPGAs)Many LUT architectures have been studied; nevertheless, it is difficult to quantificationally evaLUT based architecture. Traditionally, dedicated efforts on specific modifications to the temapping tools are required for LUT architecture evaluation. A more feasible evaluation method forfunctionality is strongly required for the design of LUT architecture. In this paper, a mathematical for logic functionality calculation is proposed and conventional and fracturable LUT architectanalyzed. Furthermore, a cascaded fracturable LUT architecture is presented, which achieves twice functionality compared with the conventional LUTs and fracturable LUTs.展开更多
The development of accurate prediction models continues to be highly beneficial in myriad disciplines. Deep learning models have performed well in stock price prediction and give high accuracy. However, these models a...The development of accurate prediction models continues to be highly beneficial in myriad disciplines. Deep learning models have performed well in stock price prediction and give high accuracy. However, these models are largely affected by the vanishing gradient problem escalated by some activation functions. This study proposes the use of the Vanishing Gradient Resilient Optimized Gated Recurrent Unit (OGRU) model with a scaled mean Approximation Coefficient (AC) time lag which should counter slow convergence, vanishing gradient and large error metrics. This study employed the Rectified Linear Unit (ReLU), Hyperbolic Tangent (Tanh), Sigmoid and Exponential Linear Unit (ELU) activation functions. Real-life datasets including the daily Apple and 5-minute Netflix closing stock prices were used, and they were decomposed using the Stationary Wavelet Transform (SWT). The decomposed series formed a decomposed data model which was compared to an undecomposed data model with similar hyperparameters and different default lags. The Apple daily dataset performed well with a Default_1 lag, using an undecomposed data model and the ReLU, attaining 0.01312, 0.00854 and 3.67 minutes for RMSE, MAE and runtime. The Netflix data performed best with the MeanAC_42 lag, using decomposed data model and the ELU achieving 0.00620, 0.00487 and 3.01 minutes for the same metrics.展开更多
低延迟分组密码的设计是目前密码学研究中的热点之一,其中低延迟S盒的构造是设计中的重要研究方向.本文基于低延迟门电路和两层树型结构,搜索不同延迟水平下具有一定密码学性质的低延迟平衡布尔函数及其拓展比特置换等价类;基于将低延...低延迟分组密码的设计是目前密码学研究中的热点之一,其中低延迟S盒的构造是设计中的重要研究方向.本文基于低延迟门电路和两层树型结构,搜索不同延迟水平下具有一定密码学性质的低延迟平衡布尔函数及其拓展比特置换等价类;基于将低延迟布尔函数作为分量布尔函数构造向量布尔函数的方法,本文构造得到了不同延迟水平下的低延迟S盒,并给出延迟性质和硬件实现面积具有优势的S盒实例;此外,本文对低延迟的S盒集合与逆S盒集合匹配搜索具有双向低延迟性质的S盒,给出搜索得到的实例.与PRINCE、MANTIS等其他低延迟分组密码中使用的4 bit S盒相比,本文构造的低延迟S盒在延迟水平上相较MANTIS降低了20%,与PRINCE相比降低了33%,在硬件实现面积上相较MANTIS减少了6.68%,与PRINCE相比减少了17.69%.展开更多
作为常见的高迁移率直接带隙半导体,砷化镓(gallium arsenide,GaAs)的光电响应性质一直是学界研究的焦点.针对特殊结构半导体器件的光电响应方式理论上研究一般采用宏观有限元方法结合半经典理论的模拟.随着器件尺寸的小型化,微观结构...作为常见的高迁移率直接带隙半导体,砷化镓(gallium arsenide,GaAs)的光电响应性质一直是学界研究的焦点.针对特殊结构半导体器件的光电响应方式理论上研究一般采用宏观有限元方法结合半经典理论的模拟.随着器件尺寸的小型化,微观结构的重要性更加凸显.通过非平衡态格林函数结合密度泛函理论方法(non-equilibrium Green’s function method with density functional theory,NEDF-DFT)首次在原子尺度下计算了砷化镓纳米结在化学掺杂和栅极下的光响应,定性分析了材料掺杂浓度对光响应的影响.本工作对于半导体器件光电性质的模拟分析方法的拓展和器件性能的定性理解具有比较重要的意义.展开更多
文摘By applying nonequilibrium Green’s functions (NEGF) in combination with the density functional theory (DFT), we investigate the electronic transport properties of gated phenalenyl molecular devices with two different contact geometries. The calculated results show that electronic transport properties of the two different devices can be modulated by external transverse gates. When the molecule contacts the Au electrodes through two second-nearest sites, the current-voltage (<em>I</em>-<em>V</em>) characteristic curves are symmetric and suppressed by the gate electrodes. However, a rectifying behavior will occur when the electrodes connect the molecule on both sides, one second-nearest site and one third-nearest site, respectively. Mechanisms for such phenomena are proposed and these findings suggest a new opportunity for developing molecular devices.
文摘The electrical characteristics of a double-gate armchair silicene nanoribbon field-effect-transistor （DG ASiNR FET） are thoroughly investigated by using a ballistic quantum transport model based on non-equilibrium Green＇s function （NEGF） approach self-consistently coupled with a three-dimensional （3D） Poisson equation. We evaluate the influence of variation in uniaxial tensile strain, ribbon temperature and oxide thickness on the on-off current ratio, subthreshold swing, transconductance and the delay time of a 12-nm-length ultranarrow ASiNR FET. A novel two-parameter strain mag- nitude and temperature-dependent model is presented for designing an optimized device possessing balanced amelioration of all the electrical parameters. We demonstrate that employing HfO2 as the gate insulator can be a favorable choice and simultaneous use of it with proper combination of temperature and strain magnitude can achieve better device performance. Furthermore, a general model power （GMP） is derived which explicitly provides the electron effective mass as a function of the bandgap of a hydrogen passivated ASiNR under strain.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60936005 and 61076097)the Cultivation Fund of the Key Scientific and Technical Innovation Project,Ministry of Education of China (Grant No. 708083)the Fundamental Research Funds for the Central Universities (Grant No. 20110203110012)
文摘In this paper the influences of the metal-gate and high-k/SiO 2 /Si stacked structure on the metal-oxide-semiconductor field-effect transistor（MOSFET） are investigated.The flat-band voltage is revised by considering the influences of stacked structure and metal-semiconductor work function fluctuation.The two-dimensional Poisson＇s equation of potential distribution is presented.A threshold voltage analytical model for metal-gate/high-k/SiO 2 /Si stacked MOSFETs is developed by solving these Poisson＇s equations using the boundary conditions.The model is verified by a two-dimensional device simulator,which provides the basic design guidance for metal-gate/high-k/SiO 2 /Si stacked MOSFETs.
文摘Look Up Tables(LUTs) are the key components of Field-Programmable Gate Arrays(FPGAs)Many LUT architectures have been studied; nevertheless, it is difficult to quantificationally evaLUT based architecture. Traditionally, dedicated efforts on specific modifications to the temapping tools are required for LUT architecture evaluation. A more feasible evaluation method forfunctionality is strongly required for the design of LUT architecture. In this paper, a mathematical for logic functionality calculation is proposed and conventional and fracturable LUT architectanalyzed. Furthermore, a cascaded fracturable LUT architecture is presented, which achieves twice functionality compared with the conventional LUTs and fracturable LUTs.
文摘The development of accurate prediction models continues to be highly beneficial in myriad disciplines. Deep learning models have performed well in stock price prediction and give high accuracy. However, these models are largely affected by the vanishing gradient problem escalated by some activation functions. This study proposes the use of the Vanishing Gradient Resilient Optimized Gated Recurrent Unit (OGRU) model with a scaled mean Approximation Coefficient (AC) time lag which should counter slow convergence, vanishing gradient and large error metrics. This study employed the Rectified Linear Unit (ReLU), Hyperbolic Tangent (Tanh), Sigmoid and Exponential Linear Unit (ELU) activation functions. Real-life datasets including the daily Apple and 5-minute Netflix closing stock prices were used, and they were decomposed using the Stationary Wavelet Transform (SWT). The decomposed series formed a decomposed data model which was compared to an undecomposed data model with similar hyperparameters and different default lags. The Apple daily dataset performed well with a Default_1 lag, using an undecomposed data model and the ReLU, attaining 0.01312, 0.00854 and 3.67 minutes for RMSE, MAE and runtime. The Netflix data performed best with the MeanAC_42 lag, using decomposed data model and the ELU achieving 0.00620, 0.00487 and 3.01 minutes for the same metrics.
文摘低延迟分组密码的设计是目前密码学研究中的热点之一,其中低延迟S盒的构造是设计中的重要研究方向.本文基于低延迟门电路和两层树型结构,搜索不同延迟水平下具有一定密码学性质的低延迟平衡布尔函数及其拓展比特置换等价类;基于将低延迟布尔函数作为分量布尔函数构造向量布尔函数的方法,本文构造得到了不同延迟水平下的低延迟S盒,并给出延迟性质和硬件实现面积具有优势的S盒实例;此外,本文对低延迟的S盒集合与逆S盒集合匹配搜索具有双向低延迟性质的S盒,给出搜索得到的实例.与PRINCE、MANTIS等其他低延迟分组密码中使用的4 bit S盒相比,本文构造的低延迟S盒在延迟水平上相较MANTIS降低了20%,与PRINCE相比降低了33%,在硬件实现面积上相较MANTIS减少了6.68%,与PRINCE相比减少了17.69%.
文摘作为常见的高迁移率直接带隙半导体,砷化镓(gallium arsenide,GaAs)的光电响应性质一直是学界研究的焦点.针对特殊结构半导体器件的光电响应方式理论上研究一般采用宏观有限元方法结合半经典理论的模拟.随着器件尺寸的小型化,微观结构的重要性更加凸显.通过非平衡态格林函数结合密度泛函理论方法(non-equilibrium Green’s function method with density functional theory,NEDF-DFT)首次在原子尺度下计算了砷化镓纳米结在化学掺杂和栅极下的光响应,定性分析了材料掺杂浓度对光响应的影响.本工作对于半导体器件光电性质的模拟分析方法的拓展和器件性能的定性理解具有比较重要的意义.
