X-ray diffraction studies of silicon implanted with high-energy erbium ions

Silicon crystals after implantation of erbium ions with energies in the range 0.8–2.0 MeV and doses in the range 1×10¹²–1×10¹⁴ cm⁻² have been studied by two-and three-crystal x-ray diffraction. Three types of two-crystal reflection curves are observed. They correspond to different structural states of the implanted layers. At moderate doses (1×10¹²–1×10¹³ cm⁻²) a positive strain is observed, due to the formation of secondary radiation defects of interstitial type. An increase of the implantation dose is accompanied by the formation of an amorphous layer separating the bulk layer and a thin monocrystalline surface layer. At an implantation dose of 1×10¹⁴ cm⁻² the monocrystalline surface layer is completely amorphized. Parameters of the implantation layers are determined. A model of the transformation of structural damage is discussed. Fiz. Tverd. Tela (St. Petersburg) 39, 853–857 (May 1997)     

X-ray diffraction diagnostics methods as applied to highly doped semiconductor single crystals

Si(As, P, B) and GaSb(Si) single crystals are used as examples to demonstrate the possibilities of methods of X-ray diffraction for the diagnostics (examination of a real structure) of highly doped semiconductor crystals. Prominence is given to characterizing the state of impurity: whether it is in a solid solution or at a certain stage of its decomposition. An optimum combination of X-ray diffraction methods is found to obtain the most complete information on the microsegregation and structural heterogeneity in crystals with low and high X-ray absorption. This combination is based on X-ray diffraction topography and X-ray diffractometry methods having an increased sensitivity to lattice strains.     

X-ray diffraction study of silicon single crystals highly doped with boron

The section Lang method of X-ray diffraction topography in combination with X-ray diffractometry based on the Borrmann effect was previously shown to be effective for detection of cluster formation during the growth process of highly doped Si-Cz single crystals. In the present work, the same techniques have been used to choose the best condition of technological heat treatment of boron-doped silicon from the view-point of formation of microdefects. The concentration and average size of dislocation loops have been calculated for two conditions of standard heat treatment from the analysis of diffusion scattering. The distribution of dislocation loops along the growth axis and crystal diameter has been determined as well.     

Structural studies of disordered carbons by high-energy X-ray diffraction

X-ray diffraction measurements were carried out on three samples of disordered, commercially produced carbons, AX21, CXV and BP71, on the ID15B beam-line at the European Synchrotron Radiation Facility (ESRF), Grenoble. Intensity data were converted to pair correlation functions via the Fourier transform. The results obtained show that the structure of the studied samples consists of one–four graphite-like layers, stacked without spatial correlations. The size of the ordered regions is in the range of 9–16?Å. The atomic arrangement within an individual layer can be described in terms of the paracrystalline ordering, in which lattice distortions propagate proportionally to the square root of interatomic distances. The paracrystalline structure was simulated by introducing the Stone–Wales defects (pair of two pentagons and two heptagons), randomly distributed in the network. The resulting structures were relaxed using the reactive empirical bond order potential for carbon–carbon interaction and the Lennard-Jones potential with parameters for interlayer interactions. Such defects lead to curvature of individual layers.     

Analytical treatment of surface resonance diffraction of high-energy electrons

The surface resonance RHEED problem is solved exactly using the tight-binding model for the case of the off-Bragg orientation of the incident beam. Explicit expressions are obtained for the wave function and for the resonance part of the surface reflectivity. It is shown that the dominant contribution to the reflectivity results from a process involving at least several states each localized in the potential of adjacent atomic planes parallel to the surface, and in the crystal bulk the wave function of the scattering problem belongs to the continuum of Bloch states. The analytical solution found provides an accurate approximation to the results of numerical integration of the relevant equations of the theory of RHEED, and demonstrates that no concept of a surface state is required for interpretation of the angular dependence of the reflectivity of a clean crystal surface in the vicinity of the resonance condition.     

Site-specific recoil diffraction of backscattered electrons in crystals

A novel diffraction effect in high-energy electron backscattering is demonstrated: the formation of element-specific diffraction patterns via nuclear recoil. For sapphire (Al(2)O(3)), the difference in recoil energy allows us to determine if an electron scattered from aluminum or from oxygen. The angular electron distribution obtained in such measurements is a strong function of the recoiling lattice site. These element-specific recoil diffraction features are explained using the dynamical theory of electron diffraction. Our observations open up new possibilities for local, element-resolved crystallographic analysis using quasielastically backscattered electrons in scanning electron microscopy.     

On the possibility of diagnostics of high-energy proton beams using parametric X-ray radiation excited in single crystals

The possibility of diagnosing high-energy proton beams with the help of parametric X-ray radiation generated in single crystals is considered.     

Precipitation in silicon wafers after high temperature preanneal studied by X-ray diffraction methods

We have investigated oxygen precipitation in Czochralski silicon wafers focusing on influence of nucleation temperature and high temperature pre-anneal during common three step treatment. Thick Si wafers were studied mainly by x-ray diffraction in Laue transmission geometry using Mo x-ray tube, but were also compared to reciprocal space maps obtained in Bragg reflection geometry. The analysis of measured diffraction scans in Laue geometry was performed by means of Takagi equations and statistical dynamical theory of diffraction. From the simulated Laue diffraction curves we find the size of the individual defect area and the fraction of strain area volume in the wafer. The results obtained from x-ray diffraction were compared to loss of interstitial oxygen according to infrared absorption spectroscopy and the size of SiO₂ precipitate core was estimated. These techniques are in agreement with transmission electron microscopy images.     

Epitaxial film crystallography by high-energy Auger and X-ray photoelectron diffraction

We review recent work in the application of Auger and X-ray photoelectron diffraction at high electron kinetic energies to the problem of structure determination in ultrathin epitaxial overlayers. These closely-related techniques are based on the fact that outgoing Auger and photoelectrons from single-crystal specimens undergo elastic scattering and interference from near-neighbour atoms in the vicinity of the emitter. Such coherent diffraction leads to large intensity modulations as the detected emission direction is varied with respect to the crystal axes of the specimen. The measured modulations are readily interpreted by means of model quantum mechanical scattering calculation in which atomic coordinates in the epitaxial film are systematically varied. Such analyses provide several kinds of useful information, including growth modes accompanying heteroepitaxy, structural details of alloy and compound formation, and quantitative determination of tetragonal distortion at lattice-mismatched heterointerfaces. After a discussion of experimental design and theoretical modelling, we present several case studies of heteroepitaxial growth involving dissimilar materials. In addition, we review the new subfield of Auger and photoelectron holography, and discuss the current state-of-art in both data acquisition and Fourier inversion of experimental data for directly obtaining structural parameters.     

Production of transversally polarized high-energy electrons and positrons in crystals

It is shown that the production of transversally polarized electrons and positrons by unpolarized γ-quanta with energies of tens and hundreds of GeV, is possible in thin crystal plates.     

On the generation of bulk microdefects in phosphorus-diffused monocrystalline silicon solar wafers after a high-thermal treatment studied by X-ray topography

Oxygen is the most important impurity in free dislocation Czochralski silicon single crystals incorporated interstitially during the growth. The knowledge of oxygen behavior after thermal processes is of great technological importance, since different kinds of bulk microdefects such us SiO₂ precipitates, dislocation loops and stacking faults can be generated. In monocrystalline silicon solar cell manufacturing fabrication, there are several high-thermal treatments. The first is the diffusion process at 850–900 °C. Three different kinds of phosphorus diffusion wafers, standard PO₃Cl liquid, spray-on and screen printing, were comparatively studied by X-ray topography showing that phosphorus diffusion improves the crystal quality by a gettering process whose best efficiency is in PO₃Cl-diffused wafers. Later, another fabrication high-thermal step is for instance the rear surface passivation taking place at temperatures from 800 to 1,050 °C. For this reason, it is important to study how a high-thermal treatment at 1,000 °C affects the different phosphorus-diffused wafers mentioned above. To evaluate and characterize the possible defects induced by the oxygen precipitation, X-ray topography has been employed. Results show that annealed wafers are not perfect crystals; the oxygen precipitation induces the generation of bulk microdefects whose kind, size and density depend on the diffusion method employed. In PO₃Cl and spray-on diffused wafers, retardation in the oxygen precipitation process takes place after annealing, while in screen printing this process is recovered and a kind of mixed defects between dislocation loops and platelet precipitates is generated.     

Structure of molten silicon and germanium by X-ray diffraction

X-ray diffraction patterns have been obtained from molten silicon and germanium near the melting point. In both cases the structure factor was a low first peak maximum with a small hump on its high angle side in contrast with those of simple molten metals such as sodium and aluminum. It was also found that the pair correlation functions for these molten elements are characterized by a low peak maximum which follows the usual first peak maximum corresponding to the nearest neighbour distance. The electrical resistivity and thermoelectric power have been calculated on the Ziman theory using thet-matrix of muffin-tin potential based on the structural data observed in this work. Good agreement was found in most cases.     

X-ray diffraction study of the effect of neutron irradiation on the defect formation in silicon crystals grown by the Czochralski method and annealed at high temperatures

The effect of x-ray scattering by neutron-irradiated and reference (unirradiated) silicon crystals grown by the Czochralski method and annealed at temperatures of 850–1050°C on the defect formation is comparatively investigated using triple-crystal x-ray diffractometry. The sizes and concentrations of clusters composed of point defects and dislocation loops formed during decomposition of an oxygen-containing solid solution and subsequent clusterization of the point defects are calculated.     

A Combined optical and X-ray diffraction study of polytypism in cleaved CdI2 crystals

A comprehensive observation on the growth processes in polytypic crystals of CdI₂ grown from solution has been made in situ and correlated with the internal structures of the crystals, determined by X-ray diffraction after repeated cleavages.

Theoretical estimates of the growth parameters α and β indicate that the crystals should grow through a combined operation of two-dimensional nucleation and spiral growth, which has been confirmed experimentally. It is concluded that the growth mechanism has no direct bearing on the formation of polytypes, which really seems to be governed by thermodynamic factors.     

利用飞秒激光等离子体产生的超热电子进行衍射实验的可行性研究

利用高强度超短脉冲激光与铝靶相互作用可以产生高能超热电子,这些超热电子入射到铝单晶上时将发生衍射.对高强度超短脉冲激光产生的超热电子与晶体的相互作用产生衍射及利用这样的衍射进行晶体结构分析的可行性进行了探讨 关键词： 等离子体 超热电子 衍射 晶体