氮化硅膜致小尺寸金属氧化物半导体晶体管沟道单轴应变物理机理

应力作用下MOS性能可显著提升, 小尺寸MOS沟道中单轴应力的引入可通过在MOS表面覆盖淀积SiN膜实现. 虽然该工艺已广泛应用于MOS性能的提升, 但有关SiN膜致MOS沟道应力的产生机理、作用机理, 以及SiN膜结构与MOS沟道应力类型关联性等方面的研究仍需深入探讨. 本文基于ISE TCAD仿真, 提出了分段分析、闭环分析和整体性分析三种模型. 通过对Si MOS源、栅、漏上多种SiN膜淀积形式的深入分析, 揭示了SiN膜致MOS 沟道应力产生与作用物理机理. 研究发现: 1) “台阶”结构是SiN膜导致MOS沟道应变的必要条件; 2) SiN膜具有收缩或者扩张的趋势, SiN膜主要通过引起MOS源/漏区域Si材料的形变, 进而引起沟道区Si材料发生形变; 3)整体SiN膜对沟道的应力等于源/漏上方SiN膜在源/漏所施加的应力、“闭环结构”对沟道内部所施加的应力以及SiN膜的完整性在沟道产生的应力的总和. 本文物理模型可为小尺寸MOS工艺制造, 以及MOS器件新型应力引入的研究提供有价值的参考.     

EAST超导托卡马克装置主机支撑结构极低温条件下应力应变分析

报道了国家"九五"重大科学工程EAST超导托卡马克核聚变实验装置中心液氦冷却冷质部件的钢/高分子复合材料支撑装置在模拟冷却收缩条件下的应力应变分析结果。单个支撑结构由高分子复合材料桶状结构固定在垂直薄板板簧结构上部组成。实验表明该支撑装置在顶部水平负荷作用下发生S型扭曲,而不是简单的悬臂梁式形变。支撑部件整体在试验范围内,在常温、低温条件下均对外加顶部水平推力呈线弹性形变。但在低温下,环氧树脂部件与不锈钢板簧结合部的应变,随外力呈非线性弹性形变,这与室温下的线性变化成鲜明对照。低温下整个部件刚性增加,与常温比较,同等水平位移需要的外力增加,但是环氧树脂部件上的应力反而较常温下显著减小;不锈钢板簧底部上部与环氧部件结合部应力则显著增加。     

转动对超形变带能谱和M1跃迁的影响

利用三轴粒子－转子模型研究了转动对超形变带能谱和Ｍ１跃过的影响．给出了１９５ＴｉＳＤ带的能谱，Ｓｉｇｎａｔｕｒｅ分离，Ｂ（Ｍ１）值和Ｅ２γ跃迁强度．１９５Ｔ１Ｓｉｇｎａｔｕｒｅ伙伴带之间的Ｍ１跃迁主要通过内转换电子进行．     

铝铜合金的流变应力和形变速率的依赖关系

在液态空气温度至350℃的范围内,用在形变过程中改变形变速率和温度的方法测定了Al-Cu合金多晶体(α+θ相)的流变应力和形变速率、温度之间的依赖关系。从高温区域流变应力和形变速率的对数以及温度之间的线性关系得出激活能约为1.7eV左右,与纯铝的自扩散激活能相近。同时计算得激活体积随形变度的增大和温度的降低而减小。这些结果说明:Al-Cu合金中高温区流变应力可以用Hirsch的割阶理论来解释。在低温区域存在着另一个热激活过程,由速度效应和应力弛豫实验得出的激活体积均随形变度的增大而减小,而且二者在数值上也     

低温下双温区多管道绝热支撑设计及数值模拟研究

本文以液氢温区下的双温区多管道为研究对象, 对其进行了热流分析, 建立了几何模型, 采用有限元方法进行了热-结构耦合分析求解, 分析了不同壁厚及不同支撑宽度下漏热、 应力及形变的变化规律. 研究结果表明: 壁厚减小时, 漏热值减少, 绝热支撑总体应力增加, 支撑形变增大; 宽度减小时,20 K 温区漏热量减少,80 K 温区漏热增加, 总漏热量减少, 支撑应力增大, 最大形变量增大. 最终, 针对某工程使用的双温区四管道, 拟合出了壁厚与漏热、 最大应力及最大形变量变化规律的曲线、 方程, 宽度与双温区漏热、 最大应力及最大形变量变化规律的曲线、 方程. 在应力、 漏热、 形变量均允许的情况下, 得出最薄壁厚可取到1 .576 mm; 在壁厚取为2 mm 时, 得出最小宽度可取为0.572 mm.     

基于布里渊散射的结构应力光纤测试技术研究

本文通过分析一定功率的脉冲光射入光纤中的布里渊散射规律,介绍了分布式光纤测量测量轴向应力的基本原理。制作实验装置,测量单独的应变模型,分析散射回来的波形图,初步了解应力在光纤布里渊散射波谱上的图像特征。将应力作用于光纤的不同位置,对比它们与无应力作用诗所得到的散射波形之间的图像差异,研究其对光脉冲在光纤传输过程中的影响规律。结果表明,应力的作用大小,作用位置的不同都会对脉冲光的传播造成影响,主要在于影响布里渊散射的斯托克斯光和反斯托克斯光。本次研究所得可以为分布式光纤测量提供参考,为分布式光纤在测量微型形变的应用中有一定的促进作用。本次研究的创新点在于使用滑轮的方法,解决同等应力在分布光纤的不同位置作用效果。     

基于光纤布拉格光栅传感的锂电池内部状态原位监测

锂电池内部的应力和温度变化难以监测是影响电池安全运行的最大隐患，提出采用光纤布拉格光栅传感技术，在锂电池内部植入光栅对电池阳极的温度和应力变化信息进行实时采集，实现了对锂离子电池阳极的原位监测，建立了电信号与光学传感信号之间的联系。实验结果表明，锂电池工作循环中，锂离子的脱嵌和嵌入会引起温度变化，对应传感器波长偏移达100 pm，温度上升11.1℃；在排除温度因素的影响后，循环电流的跳变会引起阳极收缩，产生的应力使波长漂移达21.96 pm，约为18.3με。此外，研究了不同充放电速率对电池的影响，10 mA电流比2.5 mA电流时温度提高了2.8倍，应力提高了4.4倍。所植入光栅监测系统既可以高精度地测量电化学反应引起的温度、应力变化，同时解调速度快，有利于实时、准确监测锂电池的热失控及形变鼓包故障，研究结果有望为锂电池的安全使用提供有效的实验依据。     

从正常形变看超形变带角动量的确定

通过对正常形变基态转动带的研究,检验了用W-Z公式确定超形变带头角动量的方法,并与超形变带进行了对比.指出只要W-Z公式能很好地描述转动带(正常形变和超形变),同时跃迁能量灵敏地依赖于指定的角动量,由此确定的带头角动量都是正确的.     

复动量表象方法对奇特核中晕现象的研究

晕现象的研究使人们对核结构有了新的认识。连续谱，尤其是连续谱中的共振态在其中扮演着重要角色。复动量表象(CMR)方法不仅能够统一描述束缚态、共振态和连续谱，而且能够很好地描述窄共振和宽共振。本文介绍了CMR方法对原子核共振态的研究。给出了31Ne和19C等核的束缚态和共振态的单粒子能量随形变参数β₂的变化规律，分析了19C和31Ne中单中子晕形成的物理机制和在中子数N=20附近能级反转的原因，并预测了比37Mg重的核中的单中子晕现象，这一预测结果对在实验中寻找较重的晕核具有一定的参考价值。这些研究表明CMR 方法不仅适用于描述稳定核，也适用于描述具有弥散物质分布的奇特核。     

离子与原子碰撞中多电子转移的经典描述

讨论了几各地独立电子模型（ＩＥＭ）描述离子与原子碰撞中电子转移的经典模型，即Ｂｏｈｒ－Ｌｉｎｄｈａｒｄｔ模型，过垒模型ＯＢＭ和分子库仑垒模型ＭＣＢＭ。较详细阐述了描述碰撞过程的经典物理图象，着重讨论了ＭＣＢＭ描述的多电子转移过程，分析了几各模型的特点和适用性，最后在考虑了入射离子量子数亏损和出射过程电子束缚能移动的修正后，给出了修正后的ＭＣＢＭ的计算结果，并与Ｎｉｅｈａｕｓ的计算结果玫实验结果进行     

Demolding temperature in thermal nanoimprint lithography

In thermal nanoimprint lithography, temperature is one of the most important process parameters. Temperature is not only important for the flow of resist during molding but also for demolding, the process by which the imprint stamp is removed from the molded resist/substrate. This is because thermal stress and friction and adhesion forces generated at the stamp/resist interface and the mechanical strength of the resist are all dependent on temperature. In this paper, we demonstrate via both experimentation and numerical simulation that an optimal temperature (T _d) leading to minimal deformation of molded resist exists for demolding. The ease of demolding was directly accessed by measuring demolding force at different T _d for a Si stamp/PMMA/Si substrate system of 4-in.-diameter using a mechanical tester. Numerically, the demolding process for a simple two-dimensional model of a Si stamp/poly(methyl methacrylate) (PMMA) resist/Si substrate system was simulated using a finite-element method for different T _d, assuming viscoelasticity of the PMMA resist and temperature dependence of friction coefficients at the stamp/PMMA interface. We found that a temperature leading to the minimum in both the demolding force and the normalized stress vs. T _d curves exists below the glass transition temperature of the PMMA resist, from which the optimal T _d was derived.     

Structural relaxation of spin-cast glassy polymer thin films as a possible factor in dewetting

Reiter [1] has recently reported a situation in which the dewetting of quasi-solid films is linked to plastic deformation - rather than viscous flow - resulting from capillary forces. Herein we propose that, in thin films of some glassy polymers - especially poly(methyl methacrylate) (PMMA) - prepared by spin-casting from solvent, structural relaxation might impart sufficient stress to cause plastic deformation. We find that PMMA films decrease in thickness by several percent, which is sufficient to create significant stress in those cases in which the film is attached to a rigid substrate. The floating technique, which can take tens of minutes, might allow most of the structural relaxation to occur prior to dewetting experiments.Received: 1 August 2003PACS: 65.40.De Thermal expansion; thermomechanical effects - 82.60.Lf Thermodynamics of solutions - 61.41. + e Polymers, elastomers, and plasticsM. Sferrazza: Current address: Département de Physique, Université Libre de Bruxelles, Boulevard du Triomphe, CP223, 1050 Bruxelles, Belgium     

Fabrication of porous Ni–YSZ anodes by PSH-PIM

This paper has investigated the fabrication process of porous Ni–YSZ anodes by the powder injection molding method, in which a powder space holder (PSH) is used. Polymethyl methacrylate (PMMA) has been used as a PSH for mixing with NiO–YSZ powders. For this study, five kinds of feedstock containing 0%, 10%, 20%, 30%, and 40% PMMA by volume were prepared. The thermoplastic binder used for the process had a fixed 35 vol.%, and the powder loads formed the remaining 65, 55, 45, 35, and 25 vol.% of the feedstock. After molding and debinding, the parts were sintered at 1,500 °C. The obtained results showed that increasing the PMMA portion of the feedstock and reducing its powder load causes the viscosity of the feedstock to decrease. The amount of shrinkage of the samples containing 0–30% PMMA showed an almost linear increase with the increase of the PMMA content, and for the samples with 40% PMMA, this increase of shrinkage was higher. The amount of porosity in the samples having 0–30% PMMA increased with the rise in the PMMA content, but in the samples containing 40% PMMA, the amount of porosity decreased, such that it was less than that of the samples with 30% PMMA. The electrical conductivity and flexural strength of all the samples were also studied in this work.     

Numerical simulation of flat-tip micro-indentation of glassy polymers: Influence of loading speed and thermodynamic state

Flat-tip micro-indentation tests were performed on quenched and annealed polymer glasses at various loading speeds. The results were analyzed using an elasto-viscoplastic constitutive model that captures the intrinsic deformation characteristics of a polymer glass: a strain-rate dependent yield stress, strain softening and strain hardening. The advantage of this model is that changes in yield stress due to physical aging are captured in a single parameter. The two materials studied (polycarbonate (PC) and poly(methyl methacrylate) (PMMA)) were both selected for the specific rate-dependence of the yield stress that they display at room temperature. Within the range of strain rates experimentally covered, the yield stress of PC increases linearly with the logarithm of strain rate, whereas, for PMMA, a characteristic change in slope can be observed at higher strain rates. We demonstrate that, given the proper definition of the viscosity function, the flat-tip indentation response at different indentation speeds can be described accurately for both materials. Moreover, it is shown that the model captures the mechanical response on the microscopic scale (indentation) as well as on the macroscopic scale with the same parameter set. This offers promising possibilities of extracting mechanical properties of polymer glasses directly from indentation experiments.     

Elastic deformation of Ti films during alternating bending

The effect of the state of stress at a film-substrate interface on the elastic deformation of Ti films is studied during alternating bending. The Al substrate compliance is shown to cause coherent deformation of the film-substrate system, resulting in the corrugation of a Ti film and the appearance of a wavelike film-substrate interface. Fatigue tests lead to the formation of a periodic distribution of normal and tangential stresses along the interface, and this distribution favors periodic film corrugation. The corrugation of a Ti film on a Ti substrate occurs randomly in local film separation areas and is caused by defects accumulated at the interface.     

Jumpwise deformation of polymethyl methacrylate in the microplasticity region

The deformation rate with a step of 325 nm has been measured under uniaxial compression at the initial stage of creep and shape recovery of a polymethyl methacrylate (PMMA) sample after unloading. The effect of low γ-ray doses and magnetic fields on the deformation has been studied. It has been shown that a weak pre-exposure of the PMMA sample structure to radiation and magnetic fields can cause a slight hardening in the microplasticity region. The deformation jump sizes have been determined on micro- and nanoscales. The effect of irradiation and magnetic fields manifests itself as redistributed contributions of various jumps to the deformation.     

设计脆性材料的冲击塑性

通过微结构设计提升脆性功能材料的冲击塑性, 将有助于避免或延缓失效的发生. 提出在脆性材料中植入特定的微小孔洞以改善其冲击塑性的设计方法. 采用一种能够定量表现脆性材料力学性质的格点-弹簧模型, 研究了孔洞排布方式对脆性材料冲击响应的影响. 孔洞随机排布的多孔脆性材料具有明显高于致密脆性材料的冲击塑性, 而设计规则的孔洞排布方式将有助于进一步提升脆性材料的冲击塑性. 对150 m/s活塞冲击下气孔率5%的多孔样品的介观变形特征分析表明, 孔洞规则排布的样品中孔洞贯通和体积收缩变形占主导, 而孔洞随机排布的样品中剪切裂纹长距离扩展和滑移与转动变形占主导. 尽管在宏观的Hugoniot应力-应变曲线上, 两种孔洞排布方式的样品都表现出三段式响应特征(线弹性阶段、塌缩变形阶段和滑移与转动变形阶段), 但孔洞规则排布时孔洞塌缩变形阶段对整体冲击塑性的贡献更大. 研究揭示的规则排布孔洞增强脆性材料冲击塑性的原理, 将有助于脆性材料冲击诱导功能失效的预防.     

Characterisation of PMMA microfluidic channels and devices fabricated by hot embossing and sealed by direct bonding

In this study we fabricated a silicon-based stamp with various microchannel arrays, and demonstrated successful replication of the stamp micro-structure on poly methyl methacrylate (PMMA) substrates. We used maskless UV lithography for the production of the micro-structured stamp. Thermal imprint lithography was used to fabricate microfeatured fluidic platforms on PMMA substrates, as well as to bond PMMA lids on the fluidic platforms. The microfeature in the silicon-based (silicon wafer coated with SU-8) stamp includes microchannel arrays of approximately 30 μm in depth and 5 mm in width. We produced various channels without pillars, as well as with SU-8 pillars in the range of 50–100 μm wide and 6 μm in height. PMMA discs of 1 mm thickness were utilized as the molding substrate. We found 10 kN applied force and 100 °C embossing temperature were optimum for transferring the micro-structure to the PMMA substrate.     

Deformation of an elastic substrate by a three-phase contact line

Young's classic analysis of the equilibrium of a three-phase contact line ignores the out-of-plane component of the liquid-vapor surface tension. While it is expected that this unresolved force is balanced by the elastic response of the solid, a definitive analysis has remained elusive because of an apparent divergence of stress at the contact line. While a number of theories have been presented to cut off the divergence, none of them have provided reasonable agreement with experimental data. We measure surface and bulk deformation of a thin elastic film near a three-phase contact line using fluorescence confocal microscopy. The out-of-plane deformation is well fit by a linear elastic theory incorporating an out-of-plane restoring force due to the surface tension of the solid substrate. This theory predicts that the deformation profile near the contact line is scale-free and independent of the substrate elastic modulus.     

弹性基底表面薄膜起皱的计算机模拟

本文设计了一种起皱模型用以研究起皱现象的动态过程.模拟表明整个起皱过程包括三个阶段.在孵化和起皱阶段,水平方向上软基底的应力在回缩过程中传递给硬膜.而在构象松弛平衡阶段,硬膜上的应力又缓慢地传回给软基底,整个起皱过程体系的总能量持续下降.研究发现起皱后软基底上的应力集中在上表层,尤其是在波谷处.而硬膜上的应力分布则取决于方向,在垂直方向,平衡位置的应力要大于波峰和波谷处,与此相反,在水平方向应力则更集中于波峰和波谷.我们的模型既能重现起皱现象,又能重现起皮现象,为材料应力释放导致的结构失稳机理研究提供了一个非常有利的工具.