Bias dependence of a deep submicron NMOSFET response to total dose irradiation

Deep submicron n-channel metal-oxide-semiconductor field-effect transistors (NMOSFETs) with shallow trench isolation (STI) are exposed to ionizing dose radiation under different bias conditions.The total ionizing dose radiation induced subthreshold leakage current increase and the hump effect under four different irradiation bias conditions including the worst case (ON bias) for the transistors are discussed.The high electric fields at the corners are partly responsible for the subthreshold hump effect.Charge trapped in the isolation oxide,particularly at the Si/SiO 2 interface along the sidewalls of the trench oxide creates a leakage path,which becomes a dominant contributor to the offstate drain-to-source leakage current in the NMOSFET.Non-uniform charge distribution is introduced into a threedimensional (3D) simulation.Good agreement between experimental and simulation results is demonstrated.We find that the electric field distribution along with the STI sidewall is important for the radiation effect under different bias conditions.     

Mathematical Development and Verification of a Finite Volume Model for Morphodynamic Flow Applications

The accuracy and efficiency of a class of finite volume methods are investigated for numerical solution of morphodynamic problems in one space dimension. The governing equations consist of two components, namely a hydraulic part described by the shallow water equations and a sediment part described by the Exner equation. Based on different formulations of the morphodynamic equations, we propose a family of three finite volume methods. The numerical fluxes are reconstructed using a modified Roe's scheme that incorporates, in its reconstruction, the sign of the Jacobian matrix in the morphodynamic system. A well-balanced discretization is used for the treatment of the source terms. The method is well-balanced, non-oscillatory and suitable for both slow and rapid interactions between hydraulic flow and sediment transport. The obtained results for several morphodynamic problems are considered to be representative, and might be helpful for a fair rating of finite volume solution schemes, particularly in long time computations.     

等离子体浸没注入超低能注入掺杂研究

A plasma immersion ion implantation(PIII) system based on inductively coupled plasma(ICP) technology was designed. The PIII system had a cylindrical chamber, and a radio frequency(RF) power was used to sustain discharge and a pulsed voltage source was provided to bias the wafer. The RF power was coupled into chamber by a non-coplanar two-turn circular structure coil. A Langmuir probe was connected to the PIII system to diagnose the plasma parameters. The probe diagnosis indicated that plasma ion density of the system achieves 10¹⁷m^-3, the uniformity of the ion density along radial direction achieves 3.53%. Boron (B) and phosphorus (P) doping experiments were performed on the system. Results from second ion mass spectrum (SIMS) tests showed that the measured injection depth is about 10nm and the shallowest is 8.6 nm (at 10¹⁸cm^-3), the peak ion concentration is below the surface of the wafer, and the ion dose reaches above10¹⁵cm^-2 and the abrupt 2.5 nm/decade.     

Nonclassical Symmetries for Nonlinear Partial Differential Equations via Compatibility

The determining equations for the nonclassical symmetry reductions of nonlinear partial differential equations with arbitrary order can be obtained by requiring the compatibility between the original equations and the invariant surface conditions. The (2+1)-dimensional shallow water wave equation,
Boussinesq equation, and the dispersive wave equations in shallow water serve as examples illustrating how compatibility leads quickly and easily to the determining equations for their nonclassical symmetries.     

Equations of the shallow water model on a rotating attracting sphere. 1. Derivation and general properties

A shallow water model on a rotating attracting sphere is proposed to describe large-scale motions of the gas in planetary atmospheres and of the liquid in the world ocean. The equations of the model coincide with the equations of gas-dynamic of a polytropic gas in the case of spherical gas motions on the surface of a rotating sphere. The range of applicability of the model is discussed, and the conservation of potential vorticity along the trajectories is proved. The equations of stationary shallow water motions are presented in the form of Bernoulli and potential vorticity integrals, which relate the liquid depth to the stream function. The simplest stationary solutions that describe the equilibrium state differing from the spherically symmetric state and the zonal flows along the parallels are found. It is demonstrated that the stationary equations of the model admit the infinitely dimensional Lie group of equivalence. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 2, pp. 24–36, March–April, 2009.     

掺杂AgCl中光电子衰减特性研究

利用微波吸收介电谱检测技术,检测均匀掺杂[Fe(CN)_6]~(4-)盐的立方体AgCl微晶首次曝光后的自由和浅束缚光电子的衰减时间分辨谱.实验发现,随着掺杂浓度的增加,样品中自由光电子衰减时间逐渐从未掺杂时的116 ns延长至1133 ns.分析光电子衰减曲线还同时得到,随着掺杂浓度的增加,光电子的前期较慢衰减过程逐渐变快,后期较快衰减过程逐渐变慢,总体上衰减时间逐渐增加,且掺杂浓度变化对后期衰减影响较大.研究表明掺杂使得晶体中引入了能总体上延缓光电子衰减的浅电子陷阱,并且随掺杂浓度的增加,浅电子陷阱特征更加明显.     

含面内转动自由度的广义协调曲面矩形扁壳元

扁壳单元中引入结点转角自由度可以在不增加结点的情况下,增加位移场的阶次,提高计算精度,从而显著地提高单元性能。同时在单元中引入泡状位移场,能有效地扩大了单元位移场的解空间,所构造的单元具有计算精度高、对计算网格畸变不敏感的优良特性。本文利用广义协调薄板单元RGC-12的位移函数作为扁壳元的法向位移,利广义协调矩形膜元的位移函数作为扁壳面的切向位移,通过附加面内转动自由度构造了一个具有24个自由度的4结点广义协调曲面矩形扁壳元GRC-S24。在此基础上再增加一个广义泡状位移,又构造了一个具有更高计算精度的曲面矩形扁壳元GRC-S24M。并通过实例分析对这两个单元的收敛性和精度进行了验证。     

双层网格圆底扁球壳的非线性稳定问题

从基于等效夹层壳思想的双层网格扁壳,非线性弯曲理论的变分方程出发,利用坐标变换方法和驻值余能原理,导出双层网格圆底扁球壳,在均布压力作用下的轴对称大挠度方程和边界条件．采用修正迭代法,求得了两类边界条件下双层网格圆底扁球壳的非线性载荷-位移关系式和临界屈曲载荷的解析表达式,并讨论了几何参数对临界屈曲载荷的影响．     

High-resolution numerical model for shallow water flows and pollutant diffusions

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