Triple-crystal Diffractometry Research Articles

The Effect of In Situ Surface Treatment on the Growth of 3C-SiC Thin Films on 6H-SiC Substrate - An X-ray Triple Crystal Diffractometry and Synchrotron X-ray Topography Study

The Effect of In Situ Surface Treatment on the Growth of 3C-SiC Thin Films on 6H-SiC Substrate - An X-ray Triple Crystal Diffractometry and Synchrotron X-ray Topography Study

Statistical dynamical theory of X-ray diffraction in the Bragg case: application to triple-crystal diffractometry

The statistical dynamical theory of X-ray diffraction is developed for a crystal containing statistically distributed microdefects. Fourier-component equations for coherent and diffuse (incoherent) scattered waves have been obtained in the case of so-called triple-crystal diffractometry. New correlation lengths and areas are introduced for characterization of the scattered volume.

Reciprocal Space Mapping and Reflectivity Investigations of Epi-Ready InP Substrate

InP single crystals are used to the growth of three-component epitaxial layers and superlattices. Triple crystal X-ray diffractometry and reflectometry have been used to determine defects in InP epi-ready wafers caused by the mechanical treatment. Reciprocal space maps around 400 lattice points were separately made for mechanically polished wafers before and after etching treatment. The lattice imperfections have been studied by measuring the diffusion scattering. The surface morphology has been controlled by means of X-ray reflectometry.

Determination of Total Reflectivity and Diffraction Parameters of Structure Perfection of Silicon Monocrystals by Triple-Crystal X-Ray Diffractometry

A method for structure perfection diagnostics of slightly distorted crystals under X-ray diffraction in Bragg geometry is considered. The approach is based on measurement of total integral intensity of separate coherent and diffuse components of a reflected beam by triple-crystal diffractometry in (n, -n, n) geometry. This allows to calculate the value of the static Debye-Waller factor and of coefficients of additional radiation energy losses under coherent and diffuse scattering on the defects. We studied symmetric reflections from (111) and (400) planes of silicon for CuK α1 and MoK α1 radiation. The obtained values of the static Debye-Waller factor for crystals under study are compared with calculated ones obtained from Dederichs approximate model.

Effect of Thermal Diffuse Scattering in Triple-Crystal Diffractometry with High-Energy Synchrotron Radiation

The thermal diffuse scattering around reflection 220 of a thick, perfect silicon crystal has been studied quantitatively by means of a triple-crystal diffractometer and 100 keV synchrotron radiation. The necessary fitting procedures were simplified by deriving an analytic solution to the instrumental resolution function for nondispersive setting of three perfect crystals. The temperature and q dependence of the thermal diffuse scattering are very well described, taking only acoustical phonons into account; the contribution of optical phonons has been calculated explicitly.

Grazing incidence diffraction by epitaxial multilayered gratings

Multilayered gratings have been investigated by high-resolution grazing incidence diffraction, employing non-coplanar triple crystal diffractometry. A theoretical treatment has been developed based on the distorted wave Born approximation for multilayer diffraction. Grazing incidence diffraction reveals as an optimal complement to symmetrical and asymmetrical high-resolution X-ray diffraction. The method allows to measure separately the influences of the lateral strain and the grating shape. Depth selective studies have been performed by surface gratings and buried gratings showing for the first time the evolution of the strain relaxation phenomena in strained InGaAsP surface gratings resulting from burying in InP.

Low Temperature Chemical Vapor Deposition Of 3C-SiC On 6H-SiC – An X-Ray Triple Crystal Diffractometry And X-Ray Topography Study

Highly perfect 3C-SiC thin films, on 6H-SiC deposited by the chemical vapor deposition at low temperature with various Cl/Si, H/Si and C/Si ratios were characterized by x-ray high resolution triple crystal diffractometry and double crystal topographic methods. The films were epitaxial with a low defect density present (mostly in the range of 107/cm2). X-ray topography revealed stacking faults, low angle grain boundaries, dislocations and inversion double positioning boundaries present in the film and substrate.

Novel features in the strain profile and gate oxide capacitance of through-gate-oxide implanted structures

Oxidized silicon samples were implanted with O, Si, or Ar ions. The samples were characterized by x-ray triple crystal diffractometry and metal-oxide-semiconductor admittance spectroscopy to reveal information on the nature of the ion-induced damage. The experimental results on the strain profile, gate oxide capacitance, etc., exhibited novel features. These interesting results suggest ion-damage-induced precipitation of SiO2 particles in silicon and oxidation of the silicon subsurface by the injection of the recoil O atoms from the gate oxide into the silicon subsurface, both at room temperature.

Diffuse x-ray scattering of misfit dislocations at Si1−xGex/Si interfaces by triple crystal diffractometry

Heterostructure Si1−xGex layers on (001)Si substrates with different degrees of relaxation R, ranging from the nearly pseudomorphic state to the nearly relaxed state (R∼0.8), were characterized by diffuse x-ray scattering measurements. The lattice constants a⊥ and a∥, and from these the Ge content x, the relaxation R, and misfit dislocation density Dd, were determined by single crystal diffractometry. The thickness of the SiGe layers was measured in the as-grown state by double crystal diffractometry. A standard triple crystal x-ray diffractometer was used to analyze the diffuse x-ray scattering (DXS) intensity by rotation of the analyzer crystal (ΔΘ) at a fixed sample position (α). The intensities were measured around the 004 reciprocal lattice point of the Si substrate using a wide open counter and a wide range of rotation angle (ΔΘ) for the analyzer crystal. The diffuse scattering increases steeply with increasing dislocation density up to a critical value of Dd≈5×104 cm−1. Then it reaches saturation and decreases slowly as Dd increases. This behavior can be explained by the superposition of the strain fields of neighboring dislocations above a critical density, so that only the heavily distorted regions near the dislocation core participate in scattering. This is confirmed by the fact that the DXS measured for different α values follows the Stokes–Wilson scattering ( IDXS∝q−4; q being the scattering vector). We show that the diffuse scattering technique is a very sensitive tool to detect relaxation at relatively low levels of dislocation densities Dd less than 5×104 cm−1, where diffractometric techniques that measure the lattice constants are near their resolution limits.

An Experimental Study of Ion Beam and ECR Hydrogenation of Self-Ion Implantation Damage in Silicon by Admittance Spectroscopy and X-Ray Triple Crystal Diffractometry

An Experimental Study of Ion Beam and ECR Hydrogenation of Self-Ion Implantation Damage in Silicon by Admittance Spectroscopy and X-Ray Triple Crystal Diffractometry

Measurement of the differential and integral distribution of diffuse x-ray scattering intensity from defects in thin strained layers

Double-and triple-crystal diffractometry have been used to study structural perfection of a ∼1 µm-thick Ga1−xInxSb1−yAsy epitaxial film (x=0.9, y=0.8) on GaSb. It is shown that scattering from samples of this system can be divided into coherent and diffuse. The arrangement of reciprocal-lattice points of the film and substrate in the two-dimensional intensity distribution for asymmetrical reflections argues for the absence of elastic-strain relaxation. No dislocation networks are formed, and the diffuse scattering is produced by Coulomb-type defects. Localization of diffuse scattering in reciprocal space suggests that these defects reside in the epitaxial film. The diffuse-scattering distribution in asymmetrical reflections is shown to be anomalous; namely, it extends in a direction parallel to the surface and is split into two maxima. Schemes have been proposed and realized for measuring integral distributions of diffracted intensity along the surface and perpendicular to it, and their potential for studying diffuse scattering from defects is explored.

X-Ray Scattering from Nonideal Czochralski Silicon Crystals for High Energy Synchrotron Radiation

Nonideal Czochralski (CZ) silicon crystals were characterized systematically by double-crystal and triple-crystal diffractometry in the Bragg case for high energy synchrotron radiation. The crystals were either annealed at 780°C, 1000°C, and 1170°C, or lapped, with a mean abrasive particle sizes of 13 µm, 25 µm, and 42 µm. Triple-crystal diffractometry was performed at 60 keV of the BL14 vertical wiggler of the Photon Factory and double-crystal diffractometry by use of a Mo rotating-anode X-ray generator. Physical properties of the annealed and lapped crystals were studied quantitatively with respect to mosaic spread and lattice parameter fluctuation.

Characterization of SiGe HBT-structures by double-and triple-crystal diffractometry

X-ray double- and triple-crystal diffractormetry was used to measure the rocking curves of typical SiGe heterobipolar transistor structures. The depth profile of the Ge content can be determined by simulation of the rocking curves with an accuracy of about 1 nm for the thickness of the Si-cap layer and the total thickness of the SiGe layer, and an absolute error in the maximum Ge content of less than 0.5%. Comparison of experimental and simulated curves allows a fast qualitative assessment of the structural perfection of the layer system. It is doubtful that profile of boron doping inside the SiGe layer can be characterized by X-ray diffraction methods.

X-ray Triple-Crystal Diffractometry and Transmission Electron Microscopy Characterization of Defects in Lattice-Mismatched Epitaxic Structures

X-ray triple-crystal diffractometry has been applied to heterostructures with a misfit of lattice parameters in the interfaces. Si1 − xGex/Si compositions as well as GaSb layers strongly mismatched to GaAs substrates have been studied. By use of various scans in both the Bragg and Laue geometries, the data are presented either as two-dimensional maps in the scattering plane or as the intensity distribution along the diffraction vector. The structural parameters of the layers were determined from a detailed analysis of the diffraction patterns. The X-ray diffractometry results are supported by a transmission electron microscopy study.

Structural analysis of ZnS/GaAs heterostructures grown by hydrogen transport vapor-phase epitaxy

The structural characterization of ZnS epilayers grown by hydrogen transport vapor-phase epitaxy on (100)-oriented GaAs substrates is reported. X-ray-diffraction measurements in both double-axis (DA) and single-axis modes were performed to determine the residual strain tensor and the strain temperature dependence of the epilayer in the range between 25 and 650 °C. From the analysis of the data obtained by DA measurements of several symmetric Bragg reflections at different azimuth angles and several asymmetric reflections recorded in different geometries, an orthorhombic distortion of the ZnS lattice was found. The crystallographic symmetry could be explained by an asymmetric distribution of the misfit dislocation density in the interface plane along the [011] and [01̄1] directions. The temperature dependence measurements of the strain tensor components between room temperature and the growth temperature (650 °C) allowed determination of the thermal misfit between ZnS and GaAs and the linear thermal-expansion coefficient of ZnS. Finally, triple-crystal diffractometry and secondary-ion-mass spectrometry were used to investigate the chemical nature of the ZnS-GaAs interface. The results indicate the presence of an interdiffused ZnS-GaAs interface region, whose occurrence turns out to be associated with the initial defect structure of the substrate surface before the growth.

X-ray triple-crystal diffractometry of defects in epitaxic layers

A new method is developed for calculating the correlation function of the random deformation in heteroepitaxic layers and superlattices from measurements of iso-intensity contours of diffuse X-ray scattering. The method is based on the optical coherence approach and kinematical diffraction theory. Structural models have been found that enable the correlation functions to be calculated for various types of randomly placed defects (mosaic blocks and random elastic deformation). The applicability of the method has been demonstrated by measuring the diffuse X-ray scattering from a ZnTe layer grown on a GaAs substrate. The parameters characterizing the defects were obtained from a comparison of the calculated correlation function with theoretical models.

Mapping of two-dimensional lattice distortions in silicon crystals at submicrometer resolution from X-ray rocking-curve data. Erratum

Lattice distortions perpendicular to the surface in thin surface layers of ion-implanted (111) silicon crystals have been mapped as a function of depth and lateral position with resolutions of 0.05 and 0.65 μm, respectively. X-ray triple-crystal diffractometry data were collected near the fundamental 111 and satellite reflections from samples with periodic superstructure modulations in the lateral direction. 300 keV B+ ions implanted through surface mask windows are found to produce lattice distortions in a very thin layer of 0.15 μm thickness at 1.05 μm depth below the surface, with interplanar lattice spacings normal to the surface increased by several parts in 104. The distortions are appreciably extended in the lateral direction, suggesting diffusion of the ions. A 0.5 μm-thick thermal oxide strip is found to contract the interplanar spacing of substrate silicon crystal under the strip region by a few parts in 104, while the strain field created by the parallel oxide edges extends beyond a depth of 3 μm. A practical procedure is also described for arriving at a solution of the phase problem in the case of a strain field involving heavily distorted layers.

Mapping of two-dimensional lattice distortions in silicon crystals at submicrometer resolution from X-ray rocking-curve data

Lattice distortions perpendicular to the surface in thin surface layers of ion-implanted (111) silicon crystals have been mapped as a function of depth and lateral position with resolutions of 0.05 and 0.65 μm, respectively. X-ray triple-crystal diffractometry data were collected near the fundamental 111 and satellite reflections from samples with periodic superstructure modulations in the lateral direction. 300 keV B+ ions implanted through surface mask windows are found to produce lattice distortions in a very thin layer of 0.15 μm thickness at 1.05 μm depth below the surface, with interplanar lattice spacings normal to the surface increased by several parts in 104. The distortions are appreciably extended in the lateral direction, suggesting diffusion of the ions. A 0.5 μm-thick thermal oxide strip is found to contract the interplanar spacing of substrate silicon crystal under the strip region by a few parts in 104, while the strain field created by the parallel oxide edges extends beyond a depth of 3 μm. A practical procedure is also described for arriving at a solution of the phase problem in the case of a strain field involving heavily distorted layers.

Triple crystal x-ray diffractometry of periodic arrays of semiconductor quantum wires

Kinematical diffraction theory and the optical coherence formalism have been used for calculating the diffuse x-ray scattering from periodic quantum wires. The method calculates the distribution of the diffusely scattered intensity in the reciprocal lattice plane. The simulated distributions have been compared with those measured on a InAs/GaAs quantum wire by means of triple crystal x-ray diffractometry and a good agreement has been achieved. The method can be applied to studies of internal stress relaxation in quantum wires.

X-ray double and triple crystal diffractometry of mosaic structure in heteroepitaxial layers

X-ray diffraction in thin layers containing small randomly placed defects is described by means of the kinematical diffraction theory and optical coherence formalism. The method enables us to calculate both the diffracted intensity and its angular distribution, so that it can be used for simulating double crystal and triple crystal x-ray diffractometry experiments. The theory has been applied to experimental data obtained from diffractometry measurements of an epitaxial ZnTe layer with mosaic structure after several steps of chemical thinning. A good agreement of the theory with experiments has been achieved.