硅完美晶体器件与工艺

一、概述完美品体的研究即常说的晶体微观缺陷的研究。晶体的完美与缺陷是对立统一地存在。晶体中存在着缺陷就叫晶体的不完美性,理想的无缺陷的晶体称为完美晶体。晶体中的缺陷有两大类:宏观缺陷和微观缺陷。宏观缺陷常见的有小亮点、星形缺陷、球状体、多晶点、乳突、划痕等;微观缺陷常见的有位错和层错。层错是目前国内外研究微观缺陷的中心,层错除外延层错外还有热氧化堆垛层错等。位错研究中心是晶体形变而产生的位错。完美晶体对提高器件的可靠性、重复性以及封装密度是非常重要的。因为缺陷会影响器     

TMDs和黑磷二维材料与器件的制备表征及光电性能调控

正二维材料是厚度只有一个或几个原子层的晶体材料,所有原子都在二维平面内成键,层间只有范德华相互作用力。最早被发现的二维材料是2004年从石墨中被分离出来的石墨烯。后来人们又陆续发现了大量的二维材料,涵盖了导体、半导体和绝缘体,其中半导体二维材料最受关注,如过渡金属二硫族化物(TMDs)和黑磷。二维材料众多的家庭成员和丰富的特性构成了组成复杂纳米机电系统的所有基本元素。二维材料前所未有的物理、光电特性使其具有十分广阔的器件应用前景。单原     

超高速磨削切屑去除机理的分子动力学仿真研究

利用分子动力学建立了超高速磨削的物理模型和数学模型,模型包括边界原子层、牛顿原子层和恒温原子层。运用Tersoff势函数对磨粒原子和工件原子之间的相互作用力进行计算。建立了模拟的运动方程,对其进行数值求解,从而获得工件原子变化后的位移和速度。模拟了不同磨削深度下切屑的形成情况。讨论磨削深度对切屑形成过程的影响,研究了超高速磨削冲击成屑的机理。     

轴承零件锻造工艺(2)

第二章锻造的基本原理 一、金属的构造与钢的组织 1.金属的构造 一切物质都是由原子组成。固态物质内的原子排列类型有两种:一种为原子的排列呈无规律性,构成非晶体类固态物质,例如松香、玻璃;一种为原子按照一定的规律排列,构成晶体类固态物质,例如各种金属材料。     

TiN多弧离子镀过渡层的组成及其对涂层结合力的影响

论述了ＴｉＮ多弧离子镀涂层过渡层的组成及其形成机制和影响因素。实验结果及分析表明,ＴｉＮ涂层过渡层由混合及扩散层组成,扩散层包括Ｔｉ原子扩散层及Ｎ原子扩散层;影响扩散层的主要因素是基体材料的成分和沉积温度;具有Ｎ原子扩散层的过渡层将使涂层的结合力明显提高。     

单晶铜原子力显微镜加工过程亚表面变形层的分子动力学仿真

建立了原子力显微镜针尖切削单晶铜的三维分子动力学模型,采用嵌入原子势模拟工件原子之间的作用,采用Morse势模拟工件原子和刀具原子之间的作用.研究了工件材料的不同晶向和刀具切削方向、切削速度对工件亚表面变形层深度的影响.引入了原子势能变形判据,通过分析不同变形区域内原子的势能变化判断工件变形程度.观察了不同切削状态下亚表面原子势能的变化,发现工件材料晶向和切削方向对亚表面变形层深度有着显著影响.在切削速度为20～250 m/s范围内,切削速度对亚表面变形层深度没有影响.     

移动加热源法制备单层硒化镓晶体

为了解决硒化镓(GaSe)晶体制备困难、化学性能差的问题,对GaSe晶体传统的化学汽相沉积制备方法进行了改进,采用移动加热源法制备GaSe晶体。搭建了GaSe晶体的制备装置,通过单片机精确调控制备晶体的高温炉的加热温度、移动位置等参数,并采用光学显微镜和原子力显微镜对所制备的GaSe晶体进行辅助表征。研究表明,利用移动加热源法可以制备出表面光滑且尺寸较大的单层二维GaSe晶体。由于对机电设备实现了自动精密移动,可对单层二维GaSe晶体实现高质量大批量的制备,有利于GaSe晶体在光电子学和纳电子学中的广泛应用。     

蓝宝石晶体双面研磨加工的实验研究

为了实现对蓝宝石晶体的高效低损伤研磨加工,对蓝宝石晶体的双面研磨加工表面粗糙度、研磨均匀性和亚表面损伤层的深度进行试验研究。采用280#碳化硼磨粒双面研磨(0001)面蓝宝石晶体,首先考察了研磨时间对材料去除速率、表面粗糙度的作用规律,根据蓝宝石晶体切割表面状态确定了双面研磨的加工余量,接着,通过WYKO粗糙度仪从微观上分析了蓝宝石晶体表面的研磨均匀性,最后应用纳米压入测试分析了亚表面损伤层的深度。实验结果表明：蓝宝石晶体经过120分钟的双面研磨加工后可以获得Ra0.523μm,Rt<6.0μm的表面,亚表面损伤层小于1μm。     

蓝宝石超精密抛光表面的热修复机理研究

通过化学机械抛光获得的超精密蓝宝石表面存在一定厚度的表面损伤层，直接制约蓝宝石元件性能的提升。为降低蓝宝石表层损伤层，研究了蓝宝石超精密抛光表面的热修复工艺。对超精密加工后蓝宝石进行热修复处理，分析了热修复对不同晶面蓝宝石表面微观形貌的影响规律。结合蓝宝石各个晶面原子排布规律，蓝宝石C面的晶层间距最大，相比其他晶面，C面蓝宝石的超精密抛光表面更易形成台阶结构；热修复后，A面、R面蓝宝石微观表面都呈现出有序分布的台阶状结构，M面蓝宝石表面形成薄片状微观结构；在热场作用下，蓝宝石表面原子发生移动，形成台阶状形貌；纳米压痕结果表明热修复后各个晶面蓝宝石的硬度和弹性模量都有一定程度增加；通过聚焦离子束定向提取热修复前后的R面蓝宝石表层纳米厚度的薄片，并在透射显微镜下观测其高分辨原子衍射图像，证实了热修复工艺使表层原子排布由非晶态向晶体有序化转变，同时表面微观形貌也出现了规律性特征，从而使加工表面晶格完整性提升。研究结果表明热修复能有效用于蓝宝石表层质量的提升。     

二硫化钼在机械工程中的应用

机械工程中应用最广泛的固体润滑材料是二硫化钼,各种涂层和复合材料也少不了这种材料。因二硫化钼是一种分散性强、纯度高、吸附性好、不溶于水的一种层状结构材料。每层二硫化钼由三个原子平面叠合而成,两个硫原子平面中间夹有一个钼原子平面。同一原子平面中,钼原子之间以及硫原子之间由共价键键联,而两个相邻硫原子平面间靠范德华力结合,但结合强度低于层内原子间结合强度;层与层之间容易产生滑移,剪切阻力少,摩擦系数低。由于这种层状结构,决定了二硫化钼具有良好的润滑性能、化学稳定性、抗压性和附着性等特殊性能,因而广泛用于机械工程中。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.