Enhancement of several Kikuchi lines in the vicinity of spot reflections

Kikuchi electron diffraction patterns of silicon have been obtained which demonstrate the simultaneous enhancement of several excess Kikuchi lines near different point reflections. This enhancement is explained within the elementary mechanism of the formation of Kikuchi patterns while taking into account the Kikuchi electron double diffraction.     

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.     

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.     

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.     

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.     

Indicators of the magnetic state in the charge distributions of MnO, CoO, and NiO. II: Para-and antiferromagnetism of CoO

X-ray diffraction intensities from CoO were measured above and below the Néel temperature. The data were submitted to a non-parametric multipole analysis aiming at formulation of experimentally valid statements on the nature of the charge distribution. Strong “bonding maxima” are seen between the Co 〈110〉O nearest neighbors. In the paramagnetic state they are formed by the Co-ion alone, in the antiferromagnetic state they involve a strong CoO coupling. The outer electrons of oxygen give rise to slight maxima in the 〈110〉 directions, making the atom into an O^2? ion. In the paramagnetic state, their coupling with the bonding feature forms an octahedral electron cage around each oxygen atom. Broad density maxima between the atoms in 〈111〉 directions are present in both states. They connect the “bonding maxima” in the 〈110〉 directions, more strongly in the antiferromagnetic state, building up an interatomic three-dimensional network. Such electron network structures seem to be characteristic of metal oxides more generally.     

Structural characterization of silicon nanocrystals from amorphous silicon oxide materials

Silicon nanocrystals have been produced by disproportionation reaction of bulk silicon monoxide at temperatures higher than 1073 K. More specific, samples annealed at 1123, 1173, 1223 and 1323 K as well as the starting material SiO have been examined. X-ray diffraction, high-resolution transmission electron microscopy and infrared spectroscopy have been employed in order to investigate the structure of the produced silicon nanocrystals. Photoluminescence measurements reveal a three band emission with maxima positioned at 1.33, 1.52 and 1.67 eV. The intensity of the photoluminescence emission increases with the annealing temperature exponentially. This fact can be directly correlated with the disproportionation reaction which results in bigger amounts of silicon nanocrystals by increasing the annealing temperature and is discussed here. Also a possible explanation is given for the origin of each emission band.     

Synthesis and field emission properties of SnO2 nanowalls

SnO₂ nanowalls were synthesized on silicon substrate by the thermal chemical vapor transport method at a low temperature of around 650 °C under atmospheric pressure. The microstructure and morphology of the SnO₂ nanowalls were evaluated by using scanning electron microscopies and X‐ray diffraction. Room temperature photoluminescence spectra of the nanowalls showed a broad emission band centering at about 530 nm. Field emission measurements demonstrated that the nanowalls possessed good performance with a turn‐on field of ∼3.5 V/μm and a threshold field of ∼6.1 V/μm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

沉积温度对热蒸发法制备SiO2一维纳米材料的影响

利用热蒸发法在N型硅片表面成功制备出大面积SiO2纳米线和SiO2纳米棒结构.采用X射线粉末衍射(XRD),扫描电子显微镜(SEM),X射线能量色散谱(EDX),拉曼光谱(RS)和光致发光(PL)对合成的产物进行了表征.结果表明,用此方法生长的SiO2纳米材料,其结构和形貌与生长参数关系密切,随着沉积温度降低纳米线长度变短,最后呈现出棒状结构.此外,还研究了SiO2纳米结构独特的光学性质.该研究对改善光电子半导体器件的性能应用具有重要意义.     

Oberflächenbeurteilung von bearbeiteten Siliziumscheiben

For the judgement of various polished surfaces of silicon single disks was used the method of reflexion high energy electron diffraction (RHEED) in the electron microscope and on the other hand the X-ray-method of double crystal spectrometry. Because of the obtained diffraction pictures and the obtained rocking curves and because of the completing figures of surfaces with the replica method on the electron microscope, it is possible to estimate the silicon single disks relating to the mistakes in the surface range.     

The Real Structure of Ge Ions-implanted Si Crystals Subjected to Thermal Annealing

In the experiment an (111) oriented silicon plate was subjected to implantation by 80 keV Ge ions. Then, the thermal annealing of this sample was carried out in a vacuum of 5 · 10⁻⁸ Tr. The effectiveness of the annealing has been analyzed by means of X-ray topography, double crystal X-ray spectrometry and reflection high energy electron diffraction. The rocking curves in reflection and transmission as well as changes in anomalous absorption coefficient were measured. The results have been compared with effects of pulsed-laser annealing investigated by AULEYTNER et al. an thermal annealing (PRUSSIN ).     

An electron diffraction study of amorphous silicon oxide films

Amorphous silicon oxide films have been examined by high energy electron diffraction using the sector-microphotometer method of data collection common to gas phase electron diffraction. This data was analyzed with a least-squares procedure that is designed to minimize extraneous detail in the radial distribution function obtained by the Fourier sine transform of the interference function. The results of this analysis for thin film SiO₂ show that the overall bonding topology of the thin film agress well with that of bulk (vitreous) SiO₂ examined by X-ray diffraction. The experimental short distance parameters for the films whose composition was determined to be ～SiO_1.3, SiO, and SiO_0.8 are found to be consistent with those expected for a mixture of tetrahedrally bonded amorphous Si and SiO₂ phases in which the scale of the Si-like and SiO₂-like regions is of the order of a few basic tetrahedral units. This result is in agreement with previous examinations of SiO powder by X-rays and a previous examination of thin silicon oxide films by electron diffraction.     

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)     

X-ray diffraction study of the morphology and structure of pulse-anodized porous Si multilayers

Porous Si layers, obtained by pulsed electrochemical etching of n-Si(001) substrates (resistivity 0.01 Ω cm) in a 1: 1 mixture of hydrofluoric acid and ethanol, have been investigated by high-resolution X-ray diffraction and electron microscopy. The average structural parameters of the layers grown (thickness, strain, porosity, pore size) are determined. It is found that pulsed anodic oxidation leads to a decrease in the average strain of layers. It is established that, at frequencies up to 1 Hz, anodic oxidation makes obtaining porous silicon multilayers with layer thicknesses of 20–300 nm containing Si nanocrystallites possible. It is shown that X-ray diffuse scattering from pores yields information about their ordering and can be used to monitor the processes of electrochemical etching used to form porous layers.     

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。     

前驱体法制备氮氧化硅纳米线及其光学性能研究

在Ni催化剂的存在下,通过SiCl4的水解氨解反应并在1300℃氨气气氛中进行热氮化处理制得了无定形氮氧化硅纳米线.产物经X射线衍射(XRD)、热重-差示扫描量热(TG-DSC)、扫描电镜(SEM)、透射电镜(TEM)、能量色散谱(EDS)和选区电子衍射(SAED)等表征手段进行分析,结果表明纳米线为无定形结构,直径为100～150nm.在波长为220nm的光激发下,产物的光致发光光谱(PL)在563nm和289nm处分别出现了一个强的绿光发光峰和一个弱的紫光发光峰.对纳米线的生长机理进行分析,表明纳米线的生长遵循气-液-固(VLS)机制控制模式.     

Study of the structural quality of heteroepitaxial silicon-on-sapphire structures by high-resolution X-ray diffraction,X-ray reflectivity,and electron microscopy

Heteroepitaxial silicon-on-sapphire (SOS) structures have been studied by high-resolution X-ray diffraction, X-ray reflectivity, electron microscopy, and electron diffraction. These methods yielded a large amount of complementary data on the defect structure of both the sapphire substrate and the silicon film, including integral and local (at the atomic-resolution level) information about the substrate, film, and sapphire-silicon interface.     

Temperature dependent formation of microcrystal and amorphous silicon by vacuum evaporation

In silicon films deposited in vacuum by electron beam evaporation of solid silicon, the substrate temperature dependence of the formation temperature of amorphous silicon and crystalline silicon is determined. On steel and alumina substrates, below 520°C, the silicon film is amorphous. Above this temperature, the film is crystalline with a pronounced optical band gap of 1.7 eV. With thermal treatment in vacuum, a transformation from an amorphous to a crystalline state is observed at 650°C.     

Preparation and characterization of Si sheets by renewed SSP technique

Silicon sheets from powder (SSP) ribbons have been prepared by modified SSP technique using electronic-grade (9N purity) silicon powder. The surface morphology, crystallographic quality, composition and electric properties of the SSP ribbons were investigated by surface profiler, X-ray diffraction (XRD), scanning electron microscopy (SEM), metallurgical microscope, Auger electron spectroscopy (AES) and four-point probe apparatus, respectively. The results show that the SSP ribbon made from electronic-grade silicon powder is a suitable candidate for the substrates of crystalline silicon thin film (CSiTF) solar cells, which could meet the primary requirements of CSiTF solar cell process on the substrates, including surface smoothness, crystallographic quality, purity and electric conductivity, etc.     

Crystallographic Parameters of Special Grain Boundaries in Multicrystalline Silicon

Crystallography Reports - The orientation of grains and the special boundaries formed by them in multicrystalline silicon has been studied by electron backscattered diffraction. It is found that...