聚焦离子束制备透射电子显微镜样品的两种厚度判断方法

透射电镜样品的厚度是透射电镜(TEM)表征中一个重要参数,快速准确地判断样品厚度是制备高质量样品的前提.本文通过使用聚焦离子束(FIB)制备了带有厚度梯度的透射电镜样品(Si、SrTiO3和LaAlO3),并提出两种制样过程中快速判断厚度的方法.第一种通过扫描电子显微镜(SEM)的衬度变化经验地判断样品的厚度;第二种是用FIB在样品边缘切一个斜边,通过SEM测量斜边侧面的宽度用几何方法推断样品的厚度.这两种方法都通过会聚束电子衍射(CBED)和电子能量损失谱(EELS)测量的厚度作为检验标准.对比认为,样品较薄时用SEM衬度测厚比较合适;样品比较厚时用几何方法测量比较直接.     

利用平晶谱仪测量谱线波长的新方法

为了满足激光等离子体X射线波长测量的需要,在辅助光阑法的基础上,从理论上提出了一种用平面晶体谱仪确定波长的新方法.发展了改进的辅助光阑法来确定晶体面与记录面的交线到第一条辅助光阑的距离,并且利用某一条谱线的曲率得到记录面与晶体表面的夹角.这两个参量在一般的辅助光阑法中需借用参考谱线得到,而采用新的方法可在不使用任何参考谱线的情况下得到所有光谱线的波长.实际使用中通过增大光阑间的间距,根据不同的波长范围调节晶体与记录面的相对位置,可使波长的测量精度达1×10-3nm.     

硬边衍射光束的计算模拟

在激光的产生和传输过程中或多或少地要受到光阑的限制。因此,光束通过有硬边光阑限制光学系统传输问题的研究有重要实际意义。为此,已发展了多种模拟方法。一般情况下,对Collins公式直接数值积分是一种精确的模拟方法。但当光阑数增加时,计算变得非常繁琐和费时。使用四种简明方法,即解析公式法、递推算法、复高斯函数展开法和矩阵表示法来模拟硬边衍射光束,对这些方法的优点和使用范围作了分析．讨论了方法的改进。     

齿形光阑聚焦特性的研究

采用一种简单有效的方法,模拟了光束经圆形孔径和不同齿形光阑的远场衍射分布,并与经圆孔硬边光阑的衍射作了比较.另外,讨论了齿形光阑的参数对光束衍射特性的影响.结果表明,齿形光阑能有效抑制光强的高频衍射,并降低横向光强分布的不均匀性.     

高能激光系统中齿形切趾光阑的聚焦特性研究

为了提高高能激光系统光束质量,采用理论和实验相结合方法,对圆孔光阑和齿形切趾光阑的远场聚焦特性进行了理论分析和实验验证,并与圆孔光阑的远场衍射作了比较.结果表明,当圆孔光阑的硬边变成齿状的软边时,远场衍射的次极大值在一定程度上会降低;当齿状光阑齿数增多时,远场衍射光斑周边辐射状的穗状条纹将变得均匀,而且能量密度减弱,仅为峰值能量的0.01.理论和实验相符合,对指导齿形切趾光阑的制作和在激光工程中应用具有重要的参考意义.     

精确测量孔径光阑面积的光学方法

精确测量孔径光阑的面积对降低辐射测量和光度测量的不确定度具有重要的意义.根据辐射照度与面积的基本关系E=φ/A,采用制造覆盖孔径光阑恒定的照度区域方法,使等间距的激光束阵列叠加后可以形成覆盖孔径光阑的空间均匀的照度区域,通过孔径光阑的辐射通量与辐射照度的比值即为孔径光阑的面积.对该方法进行了理论分析和实验验证,得到形成均匀照度场允许的最大光束间隔,由于实际使用的光束并非理想高斯光束,因此光束间隔应小于允许间隔,对直径3mm光阑面积测量的不确定度达到3.24×10-4.该方法优越之处在于:可以不接触光阑边缘而直接测量光阑面积,无需任何已测定面积的辅助光阑,测量装置简单.     

强激光束旁瓣缩减用的软光阑

1　引言光束旁瓣缩减器 (“软”光阑 )在现代高功率激光装置的光通道中已成为广泛使用的器件。缩减器的功能是平滑光束的强度分布 ,因为用了它可以压制普通“硬”光阑造成的因衍射在光束孔径上出现的强度尖峰。这样 ,使用软光阑即可改善高功率激光束对自聚焦的稳定性。同时也可使激光束的填充因子最佳化 ,以增大激光放大器激活介质的光输出。在激光振荡器中 ,使用软光阑可使强度形成平滑分布 ,并可增加输出光束的辐射亮度。虽然提出过各种制作软光阑的方法和技术 ,但仅少数几种旁瓣缩减器被证明可实际用于高功率激光的光束通道。这种缩减器…     

FIB与PEM联用在半导体器件失效分析中的应用

在半导体器件的失效分析中,缺陷定位是必不可少的重要环节.光发射显微镜(PEM)是IC失效定位中最有效的工具之一.PEM利用了IC器件缺陷在一定条件下的发光现象,迅速定位缺陷.而聚焦等离子束(FIB)的定点切割和沉积技术在亚微米级半导体工艺失效分析中扮演着越来越重要的作用.介绍了一种联合使用FIB和PEM进行亚微米级缺陷定位的新方法,使得一些单独使用PEM无法完成缺陷定位的案例得以成功解决.     

空心高斯光束通过圆环形硬边光阑的传输特性

通过把环形光阑函数展开为复高斯函数的方法,推导出了空心高斯光束(HGBs)通过环形光阑的传输近似解析公式,并对空心高斯光束通过圆环形硬边光阑的传输特性进行了研究,分析了不同内外半径下的光阑对输出光束的影响.分析结果表明,衍射特性与空心高斯光束的阶数、光阑宽度、光阑内径等因素有关.     

光阑法变口径离子束修形仿真研究

采用一种仿真优化驻留时间分布和修形工艺的方法.通过在离子源出光口处添加光阑来改变离子束的束形,在MATLAB软件上模拟不同光阑尺寸的离子束并按照不同的叠加间距对其进行修形仿真.仿真过程中,引入修正法来获得驻留时间分布和去除面形残差分布并分析其去除规律,从而确定最佳的光阑尺寸、叠加间距和驻留时间分布.融石英平面的初始面形...     

A review of focused ion beam technology and its applications in transmission electron microscopy

The role of focused ion beam (FIB) fabrication in the development of sample preparation techniques for transmission electron microscopy (TEM) has been described in this paper. Since the repeatability of FIB sampling and TEM observations has become important, the microsampling and in situ lift-out methods are currently in wide use. Furthermore, artifacts induced during FIB milling and the consequent difficulties with energy dispersive X-ray spectroscopy are detailed. The remarkably increased capability of scanning ion microscopy and its applications are also discussed.     

Improvements in performance of focused ion beam cross-sectioning: aspects of ion-sample interaction

A gallium (Ga) focused ion beam (FIB) has been applied increasingly to 'site-specific' preparation of cross-sectional samples for transmission electron microscopy (TEM), scanning TEM, scanning electron microscopy and scanning ion microscopy. It is absolutely required for FIB cross-sectioning to prepare higher-quality samples in a shorter time without sacrificing the site specificity. The present paper clarifies the parameters that impose limitation on the following performances of the FIB cross-sectioning: milling rate, cross-sectioning at a right angle with respect to the sample surface, curtain structures formed on the cross sections, ion implantation and ion damage. All of these are discussed from the viewpoint of ion-sample interaction. Improvements for these performances achieved by diminishing their limiting origins or by correcting the resultants are described. Especially, the FIB scanning speed is significantly utilizable to improve the milling rate. A microsampling method, which allows the FIB incidence in a sidewards or upwards direction as well as downwards with respect to the microsample surface, is very effective to minimize the curtain structures.     

Application of a focused ion beam mill to the characterisation of a microstructure in tin plating on a Fe 42wt% Ni substrate

The application of a focused ion beam (FIB) mill equipped with a microsampling unit to a tin-plated specimen was reported briefly. Tin-plating has a serious problem: Whiskers are liable to grow on the surface of tinplates. In order to clarify the mechanism of the whisker growth, detail characterisation is conducted using transmission electron microscopy (TEM). However, it is difficult to prepare specimens for TEM observation without the influences of mechanical damages. It was demonstrated that FIB etching was successfully used to observe a three-dimensional microstructure by scanning ion microscopy (FIB-imaging) and to prepare thin films for TEM observation. The observation has revealed the formation of precipitates of Ni(3)Sn(4) that is considered to be strongly related to the whisker growth.     

聚焦离子束(FIB)技术及其在微电子领域中的应用

FIB是一种将微分析和微加工相结合的新技术，在亚微米级器件的设计、工艺控制和失效分析等诸多领域发挥着非常重要的作用。本文将对聚焦离子束技术及其分析、加工的机理和性能作一介绍，并对该技术在微电子领域中的应用及发展作一综述。     

A study of the damage on FIB-prepared TEM samples of AlxGa1-xAs

The damage produced by focused ion beam (FIB) milling on a TEM sample of AlGaAs crystals has been studied. The damage observed on the sidewall of an AlGaAs transmission electron microscopy (TEM) sample was an amorphous layer. The thickness of the amorphous layer linearly increased with an increase in FIB accelerating voltage from 5 to 30 kV. The thickness of the amorphous layer of Al(x)Ga(1-x)As was constant at 3 nm and was independent of the Al concentration x when the accelerating voltage was below 5 kV. The thickness of the amorphous layer of Al(x)Ga(1-x)As decreased with an increase in Al concentration x when the accelerating voltage was above 5 kV. FIB milling at 5 kV effectively minimizes the thickness of the amorphous layer and also provides flat sidewalls on multilayer samples of Al(x)Ga(1-x)As that are prepared for TEM and scanning electron microscopy (SEM).     

A method for multidirectional TEM observation of a specific site at atomic resolution

A new technique has been developed for the three-dimensional structure characterisation of a specific site at atomic resolution. In this technique, a focused ion beam (FIB) system is used to extract a specimen from a desired site as well as to fabricate the electron transparent specimen. A specimen holder with a specimen stage rotation mechanism has also been developed for use with both an FIB system and a high-resolution transmission electron microscope (TEM). The specimen holder allows both the FIB milling of a specimen and its observation in TEM without remounting the specimen from the specimen holder. A specimen for the three-dimensional TEM observation is extracted using the FIB micro-sampling technique and shaped into a pillar to mount on a tip of a needle stub enabling a multidirectional observation. The technique was applied to the multidirectional observation of the crystal structure of an Si single crystal at atomic resolution. The crystal lattice fringes of the two Si(111) planes with distances of 0.31 nm as well as the lattice fringes of the Si(200) with distances of 0.19 nm were clearly observed.     

电子束致沉积手控生长碳纳米线

用电子束致沉积(EBID)来制备各种纳米尺寸的结构在纳米材料的制备和器件构建方面有着良好的应用前景。相对于聚焦离子束(FIB),它具有对样品损伤小和所得结构尺寸更小等优点。此前,电子束致沉积的工作大多数在扫描电镜中完成,而在透射电镜中沉积直到近两年才发展起来。本文尝试在普通热发射透射电镜中,手动控制生长碳纳米线、点等结构。对碳纳米线的生长过程进行了原位观测,并对电子束斑的大小、形状和辐照时间对沉积物形状的影响作了初步的研究。最后对电子束致沉积可控生长无定型碳纳米线可能的应用作了一些探索。     

Transmission electron microscopy on thin film of high density magnetic composite prepared by FIB method

A thin specimen of a high density magnetic composite (HDMC), which is a type of powder magnetic cores was prepared for transmission electron microscopy (TEM) using a focused ion beam (FIB) method. A homogeneous thin film containing an insulator boundary between the constituent Fe powders was obtained successfully. Using this thin film, detailed flow of magnetic flux was visualized by electron holography, and the magnetic flux density was estimated to be 1.73 +/- 0.09 T being consistent with that of a bulk HDMC (1.70 T). Moreover, through Lorentz microscopy, the characteristic magnetization process of HDMC was observed by applying the magnetic field up to approximately 8 kA/m.     

Reducing focused ion beam damage to transmission electron microscopy samples

One of the most important applications of focused ion beam (FIB) systems is sample preparation for transmission electron microscopy (TEM). However, the use of the FIB inherently involves changing and damaging the sample, and thereby degrades the TEM resolution. This paper addresses the beam-induced damage and artifacts, particularly in applications involving silicon semiconductors. The damage appears in the form of amorphization on the surface of the TEM foil. The characteristics of this amorphous damage were studied by making TEM observations of cross sections of the affected foil. The damage is typically 20 to 30 nm thick for a 30 keV FIB, which is generally overly thick for modern silicon devices with feature sizes less than 250 nm. This paper reviews the reported damage depths of FIB-prepared samples, which are determined by experiments and calculations. Several damage reduction techniques, such as the use of gas-assisted etching, low energy FIB, cleaning the FIBfabricated cross section by wet or dry etching and cleaning by broad ion beam (BIB) milling have also been reviewed, with emphasis on applicability to silicon devices. We conclude that the use of low energy FIB and cleaning by argon BIB are particularly efficient techniques.     

HVEM study of crack-tip dislocations in Si crystals prepared by FIB and twin-blade cutting method

Crack-tip dislocations in silicon crystals have been examined by using high-voltage electron microscopy. Cracks were introduced by the Vickers indentation method at room temperature and the indented specimens were annealed at high temperatures to induce dislocations around crack tips under the presence of residual stress due to the indentation. A selected area around a crack tip was thinned by a focused ion beam (FIB) technique. Specimens were thinned in advance by a twin-blade cutting (TBC) method, which is a simple cutting process for saving FIB machine time. A combination of FIB and TBC can be a useful thinning procedure for the efficient preparation of transmission electron microscopy specimens. Characteristic dislocation structures were observed around the tip of a crack, aiding the elucidation of dislocation processes, which is essential to increase the fracture toughness of materials.