Mode of growth in LP-MOVPE deposition of GalnAs/lnP quantum wells

GalnAs/lnP multiple quantum wells of 10 periods grown by low pressure metal organic vapor phase epitaxy were studied using a careful analysis of their photoluminescence (PL) spectra and of supporting x-ray data. The results demonstrate extremely precise control of the well width. The width of well and barrier can be reproducibly adjusted by a fraction of a monolayer. This allows one to distinguish between 3-dimensional (3-D) and 2-dimensional (2-D) growth, which determines the lateral extent of the atomically smooth interfacial areas. By varying the growth time per well a discontinuous energy shift of the PL peaks is obtained for wells with widths from 1 to 8 monolayers. We show that this discontinuous energy shift corresponds to a change in well width by one monolayer. It is also observed when growth at the upper interface is carried on without interruption and a thin quaternary film is deposited at the interface. From these results the presence of atomically flat surfaces during the growth is deduced; these give a strong indication of a 2-D mode of growth for an optimized set of parameters.     

Reliability of AllnAs/lnGaAs/lnP HEMT with WSi ohmic contacts

We have investigated the degradation mechanism of Al_0.48In_0.52As/In_0.53Ga_0.47As/ InP high electron mobility transistors (HEMTs) using WSi ohmic electrodes. Cross-sectional transmission electron microscopy (TEM) observation and en-ergy dispersive x-ray (EDX) analysis reveal impurities diffusion of gate electrode (titanium: Ti) and fluorine (F) in the AlInAs layer after a high temperature (T_a = 170°C operating life test for 500 h. The decrease of drain current (I_ds) during life test shows linear dependence on square root of aging time. It suggests that the degradation is controlled by a diffusion mechanism. Hence, the estimated degradation mechanism of this device is related with decrease of carrier concentration in the epitaxial layer by these diffused impurities. On the other hand, TEM and EDX show no degradation of WSi/InGaAs interface after aging. Therefore, the WSi electrode for this type of HEMT demonstrates excellent high stability under the accelerated operating life test.     

表面粗糙度对太赫兹反射测量的影响

材料表面粗糙度会影响太赫兹无损检测结果。当材料表面粗糙度在微波区可以忽略不计时,在波长更短的太赫兹频段则需要考虑在内。研究讨论了在太赫兹频率下粗糙表面散射对反射谱的影响。通过考虑单个样品的反射模型,利用基尔霍夫近似可以将粗糙表面的反射信号与光滑表面的反射信号进行关联。此外,采用太赫兹时域光谱(THz-TDS)系统对不同粗糙度的葡萄糖片进行了测量,并对其反射光谱进行了分析。反射光谱结果表明,由于表面粗糙度引起的漫散射减弱了接收端反射光谱的强度。为了减小粗糙度对光谱的影响,提出了一种能恢复光谱功率的补偿方法。在0.5 THz和1 THz时,具有360目粗糙度规格样品的功率谱分别增加了约3 dB和9 dB。因此,可以认为所提出的粗糙表面光谱补偿方法在未来太赫兹无损检测技术的发展中具有一个特定的参考价值。     

材料表面粗糙度对激光吸收率影响的研究

为了在激光热处理过程中能更好地控制工件温度,并为激光热处理的数学模拟提供更为准确的激光吸收率数据,研究了材料表面粗糙度对激光吸收率的影响原理,等效处理了材料表面轮廓线,建立了数学模型,采用集总参量法测得激光的吸收率,得到的激光吸收率与理论公式计算所得的光吸收率相吻合。结果表明,所建立的模型可以准确地描述材料表面粗糙度对激光吸收率的影响,更有利于激光热处理各项参量的控制。     

表面粗糙度的激光及相关在线测量方法

随着机械加工自动化程度的提高 ,对表面粗糙度在线测量提出了越来越高的要求。目前 ,为了提高生产效率和实现生产的自动化 ,生产过程中实时检测愈加受到重视。传统的触针测量法 ,由于测量速度和测量条件的原因 ,不适于在线检测。光学测量方法近年发展很快 ,它是一种非接触测量法。根据测量原理可以归纳为干涉测量法、聚焦测量法、散射测量法、散斑测量法四种。本文重点介绍了这些技术进行表面粗糙度在线测量的原理和目前的研究结果。并对这些方法发展前景进行了分析和预测     

激光冲击成形对表面光洁度的影响

为了研究激光冲击成形对板料表面光洁度的影响,采用0.5mm厚铝板和304不锈钢板料作为试样,选择光斑直径8mm、波长1054nm、脉冲宽度23ns的激光脉冲进行冲击成形实验,铝板冲击成形的激光能量为15.4J,304不锈钢的激光能量为18.92J.冲击成形后对板料表面光洁度进行检测,结果表明,激光冲击成形可使板料表面光洁度提高接近两个精度等级.通过理论分析可知,板料背面光洁度的提高有两个方面的原因,一方面由于应力波在板料背面的微尖峰中传播时产生一系列的反射波,当反射波强度超过材料抗拉强度极限时将引起微尖峰的断裂;另一方面由于板料的高速运动在板料背面的空气中形成高压区,当作用在板料表面的空气压力大于动态屈服强度时微尖峰发生塑性变形,因微尖峰断裂和塑性变形使板料背面光洁度提高.     

激光冲击成形对板料表面质量的影响

利用0.5mm厚铝板和304不锈钢板作为试样进行激光冲击成形，试验发现激光诱导的冲击波在使板料发生塑性变形的同时，还可以显著降低板料前后表面的粗糙度。根据板料激光冲击成形的特性，从理论上分析了板料背面粗糙度降低的机理。分析表明一方面是由于应力波在板料背面的微尖峰中传播时，应力波发生反射和透射，随着尖峰的截面积逐渐减小，透射压缩波和反射拉伸波的强度逐渐增加，当反射拉伸波的强度大于材料的动态强度极限时引起了微尖峰的断裂；另一方面由于激光冲击成形中板料的高速运动，在背面的空气中形成高压背压，板料背面的微尖峰受到空气背压的压缩而发生塑性变形。由于表面微尖峰的断裂和塑性变形使尖峰高度降低，因而表面质量得到提高。     

AFM扫描参数对表面粗糙度测量的影响分析

原子力显微镜(AFM)是纳米科技研究中一个重要工具.影响AFM测量图像质量的因素很多,本文从AFM扫描参数选择的角度,研究扫描参数对样品表面均方根粗糙度的影响.实验和理论分析表明,扫描速度、反馈控制参数中的比例常数P和积分常数I的选择均对样品的表面粗糙度测量及评定产生影响.     

Field screening in (111)B InAsP/lnP strained quantum wells

Low-temperature photoluminescence measurements were performed on InAsP/InP strained quantum wells grown on InP (lll)B substrates by gas-source molecular beam epitaxy. The emission energy was observed to increase as the pump-power density increased. This was attributed to the screening of the internal piezoelectric field by photo-generated carriers. The energy shift was as large as 35 meV for an InAs_0.28P_0.72/InP quantum well with a lattice mismatch of ~0.9%. A similar structure with a smaller strain showed saturation of the energy shift with increasing pump-power density. We performed a model calculation which includes the quantum confined Stark effect, and this saturation was correlated with a flat-band structure of the quantum well due to the nearly complete screening of the built-in electric field.     

非均匀不稳定表面粗糙目标的太赫兹波段散射特性分析

研究了不同粗糙度的非均匀不稳定表面粗糙导体目标在太赫兹波段的散射特性,区别于采用经验公式的建模方法,提出把随机粗糙面的建模理念应用到太赫兹波段的非均匀不稳定表面粗糙目标的建模中,用描述随机粗糙面的均方根高度(h)和相关长度(l)两个物理量来调节目标表面的粗糙度变化.首先用高斯随机粗糙面模拟非均匀不稳定粗糙目标的表面,然后采用物理光学和等效电流相结合的方法进行仿真计算,分别对不同入射角、不同频率和不同粗糙度的不同非均匀不稳定表面粗糙导体目标,在太赫兹波段散射特性进行了分析,最后得出相关的结论.     

The effect of substrate surface roughness on the fracture toughness of Cu/96.5Sn-3.5Ag solder joints

The effects of substrate surface roughness, joint thickness, time above liquidus, and testing temperature on the chevron notch fracture toughness of Cu/96.5Sn-3.5Ag solder joints are investigated. Of these four variables,only the surface roughness of the copper surfaces to be soldered has a significant effect. A minimum fracture toughness is obtained when the average surface roughness, R_a, is between 0.2 and 1.0 μm. This encompasses the surface roughnesses produced by many cold forming operations. Decreasing the roughness to 0.04 μm increases the fracture toughness from 4.7 to 11.0 MPa√m, an improvement of 135%. Increasing the roughness to 2.0 μm increases the fracture toughness to 8.8 MPa√m, an improvement of 80%. We attribute these effects to the increased growth stresses that develop in the brittle intermetallic layer when the size scale of individual intermetallic particles is comparable to the size of the roughness features of the substrate. Two models that describe how these growth stresses might develop are provided.     

SOI纳米光波导表面粗糙度的研究进展

SOI纳米光波导表面粗糙度会显著增加波导散射损耗,降低表面粗糙度是其在许多方面应用中亟待解决的关键问题之一。首先介绍了表面粗糙度概念,总结了表面散射损耗理论方面的研究进展。随后回顾了多种SOI纳米光波导表面粗糙度测量方法,以及在表面形貌表征中存在的问题。此外,还对几种波导表面光滑工艺进行介绍,并结合具体的工作对光波导表面粗糙度各方面研究进展进行了总结。     

表面粗糙度光切显微镜测量系统的研制

以光切法测量原理为基础,采用CCD摄像头和传统光切显微镜,使用VC开发工具和图像处理技术开发了一套材料表面粗糙度测量系统。根据光切显微镜下材料表面粗糙度图像有明显方向性的特征,使用旋滤波方法对图像进行预处理,并与传统的几种滤波方法进行了比较,同时讨论了滤波窗口的大小和切线方向采用的滤波方法对粗糙度测量结果的影响。该测量系统能够测量新国标中的全部参数,并能进行在线测量。介绍了系统的标定方法,对影响测量精度的主要误差因素进行了分析,并对算术平均偏差Ra为3.2μm的标准粗糙度比较样块进行了测量,测得的结果是:Ra约等于2.93μm,相对误差约为-8.5%,低于该系统的示值允许误差。     

基于激光散斑角度相关法表面粗糙度测量

为了完成对精密机械表面粗糙度的精确测量,基于远场角度散斑强度的相关理论,采用激光散斑方法设计了表面粗糙度测量的实验光路。在实验光路中,将平面镜与待测粗糙表面固锁在一起,当转动待测粗糙表面时,平面镜与分束镜、接收屏组成了测量转动角度的光指针,提高了转动角度的测量准确度。在数据处理中,提出了基于MATLAB软件的角度散斑相关度峰值的计算方法,简化了测量步骤,提高了测量速度,进而利用相关度峰值计算求得表面粗糙度。利用设计和组建的系统对平铣表面粗糙度标准模块的表面粗糙度进行了实际测量,并对测量结果与标准样块的标称值进行比较,取得了较高的测量准确度。结果表明,此研究验证了激光散斑方法测量表面粗糙度的可行性,对进一步完善表面粗糙度的精密测量是有帮助的。     

碱性阻挡层CMP后铜布线粗糙度的影响机理分析

The surface roughness seriously affects the performance of devices after barrier CMP. Due to the high surface roughness of copper line, the local resistance of a device will be high when working, then the copper line will overheat prompting the generation of electro-migration and the circuit will lose efficacy. Reducing the surface roughness of the copper line in barrier CMP is still an important research topic. The main factors influencing the surface roughness of copper line in alkaline barrier slurry are analyzed in the paper. Aimed at influencing the law on the surface roughness of copper line, using a new type of alkaline barrier slurry with a different p H of the chelating agent and changing the content of non-ionic surfactant, we then analyze the influencing law both on the surface roughness of copper line, and the influence mechanism. The experimental results show that with a chelating agent with a low p H value in the barrier slurry, the surface roughness of the copper line is 1.03 nm and it is the lowest in all of the barrier slurries, and with the increase of non-ionic surfactant concentration, the surface roughness of copper line is reduced to 0.43 nm, meeting the demand of further development of integrated circuits.     

TiO2 薄膜CMP表面粗糙度的研究

Abstract： Surface roughness by peaks and depressions on the surface of titanium dioxide （TiO2） thin film, which was widely used for an antireflection coating of optical systems, caused the extinction coefficient increase and affected the properties of optical system. Chemical mechanical polishing （CMP） is a very important method for surface smoothing. In this polishing experiment, we used self-formulated weakly alkaline slurry. Other process parameters were working pressure, slurry flow rate, head speed, and platen speed. In order to get the best surface roughness （1.16 A, the scanned area was 10 × 10 μm2） and a higher polishing rate （60.8 nm/min）, the optimal parameters were： pressure, 1 psi; slurry flow rate, 250 mL/min; polishing head speed, 80 rpm; platen speed, 87 rpm.     

C-V characterization of SF6 plasma treated AlGaN/GaN heterostructures

We studied influence of SF₆ plasma treatment on electrical parameters of AlGaN/GaN heterostructures by C-V, I-V and SIMS measurement. We found the C-V measurements as an effective tool that is able to help to analyze electrical manifestations of charge changes in heterostructures during the semiconductor processing. In contrary to previously published results we found out that for diminishing of the two-dimensional electron gas concentration in the channel layer positively charged ions implanted during the plasma treatment into the semiconductor and not F⁻ ions are responsible.     

一种无触点快速测量表面粗糙度的方法

提出一种使用激光束快速测量表面粗糙度的无触点光学方法。一束照射在样品表面的激光束随着表面粗糙度的增大反射光的密度分布将被扩展,可用PCD测出从铝制样品表面反射光的密度分布。被反射光的密度曲线可通过高斯函数近似地求出。密度分布曲线的宽度由高斯曲线系数的标准差计算出来,此标准差近似等于密度曲线的高斯函数的标准差,密度曲线的中线平均粗糙度随着高斯曲线系数的增加而增加。粗糙度Ra在0.1～0.5μm的范围内,可利用实验公式Ra=0.088GCP+0.032通过测量GCP得到。     

高速铣削工件表面粗糙度蚁群-BP神经网络建模

由于蚁群算法具有很好的多样性、兼容性和正反馈,故十分适合用于BP神经网络学习率的优化,从而建立蚁群-BP神经网络.训练样本对是以实验1、实验3、实验5、实验7、实验9、实验11、实验13和实验15下的高速铣削试验数据组成的,并用高速铣削实验中的工件表面粗糙度来建模.使用创建的高速铣削工件表面粗糙度预测模型来对实验2和实...     

3D激光显微镜在PCB表面粗糙度研究中的应用

文章应用LEXTOLS4000激光扫描共聚焦显微镜对印制电路板芯板表面粗糙度进行测量,论述了PCB表面粗糙度测量方法及研究现状,并对其未来的研究发展方向进行了展望,以期进一步推动理论和应用研究的工作。