电子背散衍射花样的数学特征

电子背散衍射(EBSD)花样揭示了材料的物相成分、晶体结构、晶粒取向、晶粒大小和晶界的信息。EBSD花样非常复杂,通常需要借助专门的计算软件才能解析。本文系统地研究了EBSD花样的数学特征,建立了任意晶体取向与EBSD花样之间的数理关系,推导了面心立方、体心立方和六方晶体的基本晶带轴的理论EBSD花样的数学特征,以及面心立方晶体的(001)<110>取向和(001)<100>取向的理论菊池(Kikuchi)花样特征。在实测EBSD花样的分析中与各晶系各点阵的基本晶带轴的理论EBSD花样特征比较,即通过图像特征对比,就可以直接确定实测EBSD花样所属的晶系、点阵和Kikuchi线交点对应的晶带轴[uvw],再由基本晶带轴的坐标计算出晶体取向,还能提供基本晶面信息,如原子密排晶面在样品中的空间分布,这有利于晶体的变形或生长机理研究。EBSD为单晶芯片质量检验提供了新方法。     

Untersuchung gestörter Oberflächenschichten an Siliziumeinkristallen

It has been proved that by densitometric measurements of reflections of Kikuchi photograms a numeric value can be found for the quality of polished surfaces of Si single crystals. This value is given by the proportion ΔS₁/ΔS₀, characterizing the relation of the initial state of surface and the state of deeper layers, not being affected by mechanical working. This method enables to estimate the quality of crystal surfaces.     

SiC单晶片的取向研磨

优质晶体生长常常需要籽晶或衬底偏离常规结晶取向.为便于按任意偏向角度研磨晶片,本实验室设计并应用了晶片取向研磨夹具及相应的研磨工艺.本文介绍了该夹具和工艺的工作原理、技术要点以及对技术指标的鉴定情况.测试结果表明,研磨取向误差范围可控制在5;之内,研磨片厚度偏差小于5 μm、粗糙度Ra=0.12 μm.     

CdZnTe(211)面纳米力学特性分析

采用研磨-机械抛光-化学机械抛光工艺对CdZnTe(211)面进行加工,当表面粗糙度Ra达到0.94 nm时,采用纳米压痕仪对CdZnTe(211)面进行纳米力学性能测量,试验结果表明:弹性模量和硬度随着压力的增大而减小,存在明显的尺寸效应.当针尖离开晶体表面时,黏附现象特别明显.在不同晶向上,弹性模量和硬度存在显著的各向异性.     

Nonidentified Kikuchi lines with reverse contrast

Electron diffraction patterns of silicon in transmission with contrast reversal from bright to dark for an unidentified Kikuchi line along its length have been obtained. The contrast reversal of an unidentified line is explained within the elementary mechanism of Kikuchi pattern formation taking into account the Kikuchi electron double diffraction.     

单晶蓝宝石球罩的磁控研磨试验研究

开展了金刚石磁性磨料在磁场控制下研磨加工单晶蓝宝石球罩的实验,研究了研磨压力、研磨时间、乙二胺浓度等因素对单晶蓝宝石球罩材料去除率及面粗糙度的影响.实验结果表明:随着研磨压力的增大,材料去除率增加但增幅减小,面粗糙度Sa也降低,降低幅度也减小.当乙二胺浓度为3;,研磨压力为25 kPa时,材料去除率在前30 min能保持在5μm·h-1以上,但在30 min之后,材料去除率开始出现较大幅度的下降,面粗糙度Sa在前30 min较为快速地降低到110 nm左右,后30 min略有降低.     

Structure and chemical composition of LiB3O5 surfaces

The electronic and structural properties of LiB₃O₅ (LBO) surfaces have been studied by X‐ray photoemission spectroscopy (XPS) and reflectance high‐energy electron diffraction (RHEED). The as‐grown (110) crystal face and mechanically polished (001) surfaces have been investigated comparatively. Electronic structure of LBO has been determined on as‐grown (110) crystal face previously cleaned by chemical etching with RHEED control. The correlation of valence band structure and measured binding energies with earlier reported results has been discussed. Core‐level spectroscopy reveals strong enriching of mechanically polished LBO surface with carbon, when nanodiamond powder is used as an abrasive. So high carbon level as C:B = 0.7 has been observed at the surface while the ratio Li:B:O remains according to LBO chemical composition. The association of LBO Kikuchi‐lines with strong background has been shown by RHEED analysis of the surface. Thus, the polished LBO surface constitutes a high structure quality LBO with the inclusions of some amorphous carbon compound. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

磨料形貌及分散介质对4H碳化硅晶片研磨质量的影响研究

研磨作为4H碳化硅(4H-SiC)晶片加工的重要工序之一,对4H-SiC衬底晶圆的质量具有重要影响。本文研究了金刚石磨料形貌和分散介质对4H-SiC晶片研磨过程中材料去除速率和面型参数的影响,基于研磨过程中金刚石磨料与4H-SiC晶片表面的接触情况,推导出简易的晶片材料去除速率模型。研究结果表明,磨料形貌显著影响4H-SiC晶片的材料去除速率,材料去除速率越高,晶片的总厚度变化(TTV)越小。由于4H-SiC中C面和Si面的各向异性,4H-SiC晶片研磨过程中C面的材料去除速率高于Si面。在分散介质的影响方面：水基体系研磨液的Zeta电位绝对值较高,磨料分散均匀,水的高导热系数有利于控制研磨过程中的盘面温度;乙二醇体系研磨液的Zeta电位绝对值小,磨料易发生团聚,增大研磨过程的磨料切入深度,晶片的材料去除速率提高,晶片最大划痕深度随之增大。     

Homogeneity of a ZrF4-based glass at the nano-scale

A glass of composition 53ZrF₄–20BaF₂–4LaF₃–3AlF₃–20NaF (T_g=260°C) was prepared by careful crucible melting. High-resolution atomic force microscopy of fracture surfaces displayed the presence of nano-pores with diameters of 20–50 nm, being 4–10 nm deep, in all glasses. It was further found that only glasses without annealing and glasses with an annealing step considerably below T_g showed a distinct pattern, i.e. ripples of ≈20 nm in diameter and an rms roughness of ≈0.6 nm. Glasses annealed either near T_g or at the temperatures of maximum nucleation or maximum crystal growth rates showed both regions with the ripple pattern and regions with nano-hillocks, growing in size with increasing annealing temperature and time. Thus these hillocks nearly reach micro-dimensions of ≈270 nm in diameter and ≈65 nm in height following a 90 min annealing step at 343°C, the temperature of maximum crystal growth. These findings give evidence that the glass system, which is thought to be one of the most suitable for fiber drawing, is much less stable against nucleation and crystallization than anticipated.     

Measurements on anisotropy of angular distribution for the backscattering electron emission on copper monocrystals

During the perpendicular bombardment with 25 keV primary electrons the azimuthal and polar angular distribution are measured of those backscattered electrons which escape from the low index surfaces of a copper monocrystal. A movable electron spectrometer operates as a detector with the energy resolution of ΔE/E ≈ 10⁻³ and the angular resolution of Δθ = 0.5°. The observed angular distribution proves congruously with large angle Kikuchi reflection diagrams, the representation of which at metallic surfaces was successful as yet only for oblique incidence. The connection between escape direction and energy loss and also the influence of covering layers are investigated.     

Zur Realstruktur bearbeiteter Silizium-Einkristallscheiben

The production of semiconductor devices is based on single crystal silicon wafers worked by abrasive cutting, lapping and polishing. Relations between the structure of the silicon surface and the generation of dislocation are analyzed by electronmicroscopical imaging of the surface after the respective steps of mechanical treatment and by TEM after annealing.     

Electron differaction patterns with curved Kikuchi lines

Curved Kikuchi lines have been observed in electron diffraction patterns obtained for silicon by transmission electron microscopy. It is found that the curvature of Kikuchi lines is related to the shift of point reflections from their normal positions. The formation of curved Kikuchi lines stems from the local structural defects in the crystals under study.     

Helldunkel-Struktur der Kossel-Interferenzlinien und Kristallstruktur-Analyse (II). Theoretische Linienprofil-Ausläufer und Vergleich mit experimentellen Ergebnissen

As shown in part I of this paper, from a Kossel-line profile the tails are best suited for crystal structure analysis. In this part a general theoretical expression has been derived for the tails of line profile in case of different examples often observed. The theoretical results have been compared with experimental ones. As a consequence two possibilities of application in crystal structure analysis can be recommended: at first the proof of proposals of structure by the use of tails of the profiles including phase information, and secondly the direct evaluation of structure amplitudes in favourable cases. – The dark and bright fields in Kossel patterns can be explained by taking into consideration the long ranging tails of profiles. The physical similarities and differences between Kossel interferences, divergent beam interferences, Kikuchi lines and channelling patterns are considered.     

Formation and oxidation of porous silicon by anodic reaction

Porous silicon film (PSF) was formed by anodic reaction in aqueous hydrofluoric acid (HF) in the range 2 ? n < 4, n being the average number of electrons flowing through the external circuit per atom of silicon dissolved. Electron diffraction pattern of as-grown PSF changes to a very broad Kikuchi pattern from a sharp Kikuchi pattern for smaller values of n. The disproportionation reactions occur at a local point of the silicon surface for n between 2 and 4. When n is nearly equal to 2, the PSF structure changes to be amorphous and the reactions occur over the entire area of the silicon surface. The oxidation of PSF proceeds with the increase of the absorption intensities of three Si-O bands at 1070, 455, and 800 cm^-1 below 600°C, and two Si-O bands which are 455 and 800 cm^-1 above 600°C. Activation energies of Si-O bands at 1070, 455, and 800 cm^-1 at oxidation below 600°C are 0.1, 0.3, and 0.6 eV respectively. The activation energy changes remarkably below and above 600°C. The oxygen distributions in oxidized porous silicon of p-type and n-type PSF are uniform and nonuniform respectively in the thickness direction.     

Mechanism of formation of curved Kikuchi lines

The mechanism of formation of curved Kikuchi lines, observed at displacement of point reflections from their normal positions, is proposed. Curving of Kikuchi lines is explained taking into account the participation of diffracted electron beams in the formation of Kikuchi electron diffraction patterns.     

A Direct Method for Orientation Determination Using TEM (I). Description of the Method

A new method for orientation determination has been developed. The orientation of crystals of a high symmetry (especially cubic crystals) can be determined immediately while working on the transmission electron microscope (TEM). For the application of the method the TEM must be equipped with a specimen-tilt goniometer. By tilting the specimen the angles of the stereographic projection are obtained from no more than two easily identified Kikuchi poles on the screen. The stereographic projection can be constructed from these angles. The indices of the crystal orientation direction (and any other lattice direction) can be calculated from the angles between this direction and the base vectors. These angles can be measured using a Wulff net in the stereographic projection of the transmitted crystal.     

Study of X-ray diffraction from a surface acoustic wave in the grazing geometry with allowance for the curvature of the unperturbed crystal surface

Fresnel X-ray diffraction from a concave crystal surface in the presence of a surface acoustic wave (SAW) has been considered for grazing angles of incidence in noncoplanar symmetric Laue geometry. It is shown that the main peak and diffraction satellites are focused at different distances from a crystal. The effect of deviation from the Bragg angle, the spectral line width, and the SAW amplitude on the X-ray diffraction pattern has been analyzed. It is established that the contrast of an X-ray diffraction pattern of an SAW in Bragg-Laue grazing geometry is related to the character of irregularities of the crystal surface, and the pattern details depend on the measurement mode. The sensitivity of the method is about a nanometer. The focal image of the SAW serves as a scale landmark for determining the crystal surface characteristics.     

On the void distribution and size in shaped sapphire crystals

Ribbon and rod sapphire pulling has been performed in three different crystal growth equipments in order to study the effect of the installation, of the atmosphere, of the die shape, of the feed material and of the pulling rate on the distribution, number and diameter of the characteristic voids (micro‐bubbles) in the crystals. The location of the bubbles in the crystals depends on the die geometry; however, in most cases they are essentially located close to the crystal periphery and then can be efficiently removed by lapping. After statistical analysis of the results, it is demonstrated that the number of gas moles incorporated in the crystals, inside the voids, is totally independent of any growth parameter. It is also shown that the bubble diameter depends only on the pulling rate. Consequently, for a given pulling rate, the number of bubbles auto‐adjusts in order to satisfy the constant molar gas incorporation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Near-electrode processes in lanthanum-gallium tantalate crystals

The near-electrode processes on the surfaces of the polar cuts of lanthanum-gallium tantalate crystals grown in different atmospheres were investigated. The temperature dependences of short-circuit currents in the temperature range 20–700°C were measured and phase analysis of the sample surfaces after the temperature tests were performed. It is shown that short-circuit currents arise on the surfaces of polar cuts with identical conducting coatings without preliminary polarization. These currents are caused by the generation of intrinsic emf as a result of the electrochemical reactions on opposite polar cut surfaces coming in contact with a conducting coating. It is established that the crystal growth atmosphere and the conducting coating material significantly affect the temperature dependences of short-circuit currents.