- Condensed Matter Physicist/Materials Scientistedit
High resolution electron microscopy has been used to study the structure of the 3C/6H interface, Σ,=3 {111}and Σ.=3 {112}grain boundaries in 3C-SiC. In SiC, as in other compound semiconductors, anti-site bonds occur in a variety of... more
High resolution electron microscopy has been used to study the structure of the 3C/6H interface, Σ,=3 {111}and Σ.=3 {112}grain boundaries in 3C-SiC. In SiC, as in other compound semiconductors, anti-site bonds occur in a variety of defects. These are high energy bonds comparable to that of dangling bonds. But, while dangling bonds at the grain boundaries may be eliminated by reconstruction just as in elemental semiconductors, it may not be possible to avoid anti-site bonds.These problems are discussed for the Σ=3 {112} grain boundary, where the structures proposed for Ge and Si are used as starting models for SiC.
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Several problems related to the dynamics of dislocation sources and the plasticity of silicon crystals are investigated with the help of a mesoscopic simulation. The questions successively examined are the dynamics of a source of perfect... more
Several problems related to the dynamics of dislocation sources and the plasticity of silicon crystals are investigated with the help of a mesoscopic simulation. The questions successively examined are the dynamics of a source of perfect dislocations and the conditions under which perfect or partial dislocations are emitted by a source. This leads to a discussion of the initial steps of the model proposed by Pirouz for mechanical twinning and, further, to the suggestion that a relation may exist between several transitions experimentally observed at low temperatures in elemental or compound semi-conductors: a change in the slope of the yield stress vs. temperature curves, a brittle-to-ductile transition and a change in the nature of the mobile dislocations. Finally, simulations are presented of the yield point phenomenon that is a well-known feature of Si and Ge crystals. The results are discussed in terms of evolutionary laws for the total dislocation density during straining.
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ABSTRACTEpitaxial and crack-free 3C-SiC film was successfully grown on Si(100)/(111) by a one step process without separate nucleation or carbonization steps at a low temperature of 1200°C by MOVPE. The growth was achieved by using... more
ABSTRACTEpitaxial and crack-free 3C-SiC film was successfully grown on Si(100)/(111) by a one step process without separate nucleation or carbonization steps at a low temperature of 1200°C by MOVPE. The growth was achieved by using hexamethyldisilane (HMDS) with the addition of a small amount of trimethylgallium (TMG) (0.5 sccm) with dilute hydrogen (12% H2 + Ar) as a carrier gas. Without the addition of TMG during growth, epitaxial growth of SiC on Si was only possible at temperatures above 1300°C following a nucleation step at 1200∼1250°C. After growth, all the films were analyzed by using cross-sectional transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Nomarski differential interference microscopy (NDIM). It was observed by XPS that the SiC film contained only a small amount of Ga, which means the Ga component of TMG does not much accumulate in SiC, in spite of a relatively high ratio of TMG...
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A type IaB diamond specimen containing partially decomposed platelets, dislocation loops and voidites has been investigated by transmission electron microscopy. The dislocation loops were found to be prismatic and interstitial in nature,... more
A type IaB diamond specimen containing partially decomposed platelets, dislocation loops and voidites has been investigated by transmission electron microscopy. The dislocation loops were found to be prismatic and interstitial in nature, some with Burgers vector ½ a <110> previously reported, but most with Burgers vector a <001>. Burgers vector analysis of the bounding dislocation of partially decomposed platelets shows that the a <001> loops are formed by transformation of the platelets, by nucleation and climb of a <00(1— f )> dislocation, combining with the a <00 f > dislocation bounding the platelet. The climb mechanism is driven by the need to generate vacancies for the decomposition of the platelets and to accommodate the nitrogen either in small clusters in solution in the lattice or in voidites. Glide dislocations interacting with the platelets are likely to act as nucleating centres for the climb process. The ½ a <110> dislocation loops a...
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The four-point bend test was used to measure the brittle-to-ductile transition (BDT) temperature in precracked samples of semi-insulating 4H—SiC at four different strain rates. As in other semiconductors, the BDT temperature TBDT was... more
The four-point bend test was used to measure the brittle-to-ductile transition (BDT) temperature in precracked samples of semi-insulating 4H—SiC at four different strain rates. As in other semiconductors, the BDT temperature TBDT was found to be very sharp, within ±15 °C, and to shift to higher temperatures with increasing rates of the applied load (or strain rate). The results appear to be consistent with a transition temperature Tc recently observed in the yield stress of the same material as measured by compression experiments. However, strain-rate measurements in four-point bend tests are not strictly equivalent to those in compression experiments, and therefore it is difficult to directly compare the measured BDT temperatures with the yield stress transitions. Nevertheless, it is believed that the reasonable agreement between TBDT and Tc supports the model recently proposed to explain these transition temperatures.
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ABSTRACT
Research Interests: Engineering, Materials Science, Crystallography, Crystal Growth, Epitaxial Growth, and 12 moreApplied Physics, Transmission Electron Microscopy, Molecular beam epitaxy, Chemical Vapor Deposition, Mathematical Sciences, Physical sciences, Nucleation, Dislocations, High Resolution, Surface Structure, Epitaxy, and Stacking
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ABSTRACT Develops the geometrical interpretation of electron channelling patterns observed in the scanning electron microscope and derives the equations of the band edges in terms of coordinate axes located in the observation plane. A... more
ABSTRACT Develops the geometrical interpretation of electron channelling patterns observed in the scanning electron microscope and derives the equations of the band edges in terms of coordinate axes located in the observation plane. A computer program has been developed to plot and index the patterns of cubic crystals. As dynamical considerations are not included, exact matching with experimental observations is not expected. Nevertheless, the computer-drawn patterns presented show good agreement with experiment and this approach is helpful in indexing unknown lines, especially those with high indices.
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ABSTRACT
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We have grown silicon carbide (SiC) on ultrathin Si (about 300Å) and on thick Si (about 2000Å) on commercial SIMOX (from IBIS Corp and SOITEC, Inc.), and bulk Si. Electron diffraction and Rutherford backscattering spectroscopy... more
We have grown silicon carbide (SiC) on ultrathin Si (about 300Å) and on thick Si (about 2000Å) on commercial SIMOX (from IBIS Corp and SOITEC, Inc.), and bulk Si. Electron diffraction and Rutherford backscattering spectroscopy (RBS)/channeling studies indicate epitaxial growth of singlecrystal β-SiC even at growth temperatures as low as 1100°C.We have already demonstrated the fabrication of ultrathin Si, as thin as 140Å on SiO2 by using the low-energy SIMOX (LES) (20 to 30 keV) process to produce films of lower cost and excellent integrity compared to thinned commercial SIMOX. Based on these results, ultrathin Si-on-insulator (SOI) substrates appear to have great potential for device quality SiC films. However, the carbonization and/or growth of SiC on ultrathin Si requires further optimization because the processes for surface cleaning and growth of SiC on bulk Si substrates cannot be applied because of the thinness of the substrate layers. Additional carbonization work at higher t...
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The characteristic defects of 4H-SiC homoepitaxial thin films grown on bulk substrates using chemical vapor deposition (CVD) are described based on transmission electron microscopy (TEM), atomic force microscopy (AFM) and surface... more
The characteristic defects of 4H-SiC homoepitaxial thin films grown on bulk substrates using chemical vapor deposition (CVD) are described based on transmission electron microscopy (TEM), atomic force microscopy (AFM) and surface decoration studies. Emphasis is placed on understanding the formation mechanism of surface triangular defects. Cross-sectional TEM observations revealed the existence of two variants of 3C-SiC inclusions in 4H epitaxial films. In the plan-view orientation, g4H = 3304 type reflections were found useful for distinguishing the two variants of 3C-SiC platelets that are present in the 4H epilayer. A decoration technique was employed to reveal the relationship between the 3C platelets and surface features, e.g., surface steps. A formation mechanism for surface triangular defects is proposed, which is partially confirmed by the etch pit patterns obtained on the epilayer surfaces after a molten KOH etch.
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ABSTRACTDeformation experiments were carried out on 6H-SiC single crystals and the deformed samples were examined by electron-optical techniques to verify any evidence for stress-induced polytypic transformation.
ABSTRACTTransmission electron microscope (TEM) images of inversion domain boundaries (IDB) show fringe contrast, thus indicating a relative displacement between the two adjoining domains. When the IDBs are facetted, different facets may... more
ABSTRACTTransmission electron microscope (TEM) images of inversion domain boundaries (IDB) show fringe contrast, thus indicating a relative displacement between the two adjoining domains. When the IDBs are facetted, different facets may have different displacement fault vectors. This implies that when the facetting changes from one plane to another, there should be a dislocation at the intersection of the planes. This is termed an “inversion domain boundary dislocation” and it will have a Burgers vector b=R1–R2 where R1, and R2 are the fault vectors of the two facets. Experimental results for facetted IDBs and IDB dislocations in SiC grown heteroepitaxially on (001) silicon are presented.
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ABSTRACTMicro/nanopipes are linear defects along the c-axis of hexagonal polytypes of SiC and GaN that are currently the focus of much attention. It has been shown that these defects can be very detrimental to the electronic properties of... more
ABSTRACTMicro/nanopipes are linear defects along the c-axis of hexagonal polytypes of SiC and GaN that are currently the focus of much attention. It has been shown that these defects can be very detrimental to the electronic properties of devices manufactured from, at least, 6H-SiC. In this paper, the origin of these defects is discussed in terms of Frank's theory [1] that dislocations will have a hollow core when their Burgers vector is large. Two fundamental issues about such dislocations are addressed: their formation along the c-axis of the crystal, and their stability despite their large Burgers vectors [2]. The proposed model is based on the mosaic structure of sublimation-grown 6H- or 4H-SiC, and VPE-grown 2H-GaN on sapphire substrates. The presence of unit c-axis screw dislocations is attributed to the accommodation of low-angle twist boundaries in the mosaic structure. The formation of superscrew dislocations with large Burgers vector, which empty their cores to reduce ...
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Currently, large-area 3C–SiC films are available from a number of sources and it is imperative that stable high temperature contacts be developed for high power devices on these films. By comparing the existing data in the literature, we... more
Currently, large-area 3C–SiC films are available from a number of sources and it is imperative that stable high temperature contacts be developed for high power devices on these films. By comparing the existing data in the literature, we demonstrate that the contact behavior on each of the different polytypes of SiC will vary significantly. In particular, we demonstrate this for
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ABSTRACTTo reduce the defect density inherent in conventional heteroepitaxial growth of SiC on Si, selective epitaxy followed by lateral epitaxial growth was performed in a conventional atmospheric pressure chemical vapor deposition... more
ABSTRACTTo reduce the defect density inherent in conventional heteroepitaxial growth of SiC on Si, selective epitaxy followed by lateral epitaxial growth was performed in a conventional atmospheric pressure chemical vapor deposition (APCVD) system. The source gas was primarily hexamethyldisilane (HMDS). Hydrogen was used as the carrier gas and small amounts of hydrogen chloride (HCl) were added to improve the selectivity. Si(001) wafers, with an oxide layer (∼ 700 nm thick) as a mask, were used as substrates. The grown films were analyzed using optical microscopy and scanning electron microscopy (SEM). In earlier work, we had demonstrated the problems associated with the application of this technique – viz., oxide degradation and high growth temperature. Using HMDS, the growth temperature has been considerably reduced allowing the continued use of an oxide mask. Selective growth was demonstrated in films grown at 1250° and below.
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ABSTRACT Cited By (since 1996): 7, Export Date: 8 February 2013, Source: Scopus
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ABSTRACT 4H-SiC single crystals were deformed by compression in the temperature range 550 to 1300 °C and a strain rate range of 3.1 × 10–5 to 6.5 × 10–4 s–1 to determine the critical resolved shear stress for slip on the 〈 2-1-10〉(0001)... more
ABSTRACT 4H-SiC single crystals were deformed by compression in the temperature range 550 to 1300 °C and a strain rate range of 3.1 × 10–5 to 6.5 × 10–4 s–1 to determine the critical resolved shear stress for slip on the 〈 2-1-10〉(0001) primary slip system. Two different methods to determine the activation parameters for dislocation glide were examined. In the first method, where the activation enthalpy for dislocation glide ΔHg is assumed to be a function of the applied stress τ, ΔHg drops from ∼7.4 eV at τ ≈ 8 MPa to ∼2.8 eV at τ ≈ 235 MPa. In the second method, where the activation enthalpy for dislocation glide, Q, is assumed to be stress-independent, the values determined at strain rates of less than 6.3 × 10–5 s–1 were Q ≈ (2.1 ± 0.7) eV at low temperatures (T &lt; 1100 °C) and Q ≈ (4.5 ± 1.2) eV at high temperatures (T &gt; 1100 °C). Transmission electron microscopy investigations of the deformed samples show that very different configurations of dislocations are activated under the action of the applied stress. At 1300 °C, the dislocations were all perfect, albeit dissociated into leading/trailing partials separated by a ribbon of stacking fault, while at 700 °C only single leading partials, each dragging a stacking fault and without their corresponding trailing partials, were observed.
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ABSTRACT The critical resolved shear stress for activating the (0001) 〈21-1-0〉 slip system of monocrystalline 6H-SiC has been determined as a function of test temperature and strain rate via constant-displacement compression tests. Tests... more
ABSTRACT The critical resolved shear stress for activating the (0001) 〈21-1-0〉 slip system of monocrystalline 6H-SiC has been determined as a function of test temperature and strain rate via constant-displacement compression tests. Tests were conducted at temperatures between 550 and 1300 °C at strain rates of 1.3×10—4, 6.3×10ü—5 and 3.1×10ü—5 s—1. The current study shows that 6H-SiC crystals can be plastically deformed via relatively modest resolved shear stresses on the basal plane at temperatures as low as ≈550 °C. For temperatures below ≈1300 °C for the fast and intermediate strain rates, and for temperatures below ≈1100 °C for the slow strain rate, the stress exponent n, and the activation enthalpy H(2.1 ± 0.7) eV, respectively. At higher temperatures at the slowest strain rate, the activation enthalpy was determined to be (4.5 ± 1.2) eV. Subsequent to the deformation tests, transmission electron microscopy (TEM) was used to rationalize some of the results.
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A twin-twin intersection mechanism for twinning in semiconductors is presented. The mechanism is based on the disclination character of twins and accounts for all experimental findings including the diamond-hexagonal structure, the... more
A twin-twin intersection mechanism for twinning in semiconductors is presented. The mechanism is based on the disclination character of twins and accounts for all experimental findings including the diamond-hexagonal structure, the twin/matrix orientation relationship, and the shape of the intersected volume, as well as irregularities within the transformed region such as stacking faults and diamond cubic bands. The formation of long narrow diamond-hexagonal bands is proposed to be due to a similar mechanism where a second-order twin penetrates into the matrix.
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Diamond films grown on {100}, {111} boron-terminated, and nitrogen-terminated facets of cubic boron nitride (c-BN) single crystals were characterized by Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron... more
Diamond films grown on {100}, {111} boron-terminated, and nitrogen-terminated facets of cubic boron nitride (c-BN) single crystals were characterized by Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The evolution of morphology and microstructure of the diamond films at different stages during the growth process were followed by SEM investigation. The results indicate that diamond growth proceeds by nucleation of oriented three-dimensional islands followed by their coalescence. Cross-sectional TEM specimens were prepared from thick (over 10 μm) continuous diamond films grown on {111} boron-terminated surfaces. Selected-area diffraction and high resolution TEM images show that the diamond film has a parallel orientation relationship with respect to the substrate. Characteristic defects, common to diamond films obtained by chemical vapor deposition on other substrates, are also discussed.
Research Interests: Materials Engineering, Mechanical Engineering, Condensed Matter Physics, Materials Science, Raman Spectroscopy, and 12 moreMaterials, Scanning Electron Microscopy, Transmission Electron Microscopy, Boron Nitride, Nitrogen, High Resolution, Single Crystal, Cross Section, Microstructures, Three Dimensional, Growth Process, and Growth mechanism
Recent deformation experiments on semiconductors have shown the occurrence of a break in the variation of the critical resolved shear stress of the crystal as a function of temperature. These and many other examples in the literature... more
Recent deformation experiments on semiconductors have shown the occurrence of a break in the variation of the critical resolved shear stress of the crystal as a function of temperature. These and many other examples in the literature evidence a critical temperature at which a transition occurs in the deformation mechanism of the crystal. In this paper, the occurrence of a similar transition in two polytypes of SiC is reported and correlated to the microstructure of the deformed crystals investigated by transmission electron microscopy, which shows evidence for partial dislocations carrying the deformation at high stresses and low temperatures. Based on these results and data in the literature, the explanation is generalized to other semiconductors and a possible relationship to their brittle–ductile transition is proposed.
Research Interests: Materials Engineering, Mechanical Engineering, Condensed Matter Physics, Materials Science, Materials, and 9 moreTransmission Electron Microscopy, Silicon Carbide, Dislocations, Temperature Dependence, Microstructures, Low Temperature, Deformation Mechanism, Critical Temperature, and Critical Resolved Shear Stress
We report on electronic properties of single- and double-layer stacking faults in 4H-SiC and provide an insight into apparent distinctions of recombination-enhanced defect reactions at these faults. Photoluminescence imaging spectroscopy... more
We report on electronic properties of single- and double-layer stacking faults in 4H-SiC and provide an insight into apparent distinctions of recombination-enhanced defect reactions at these faults. Photoluminescence imaging spectroscopy and deep-level transient spectroscopy experiments reveal key constituents of radiative recombination and also provide firm evidence of nonradiative centers at EV+0.38eV responsible for recombination-enhanced mobility of silicon-core partial dislocations. A
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La transition fragile-ductile du polytype 4H du carbure de silicium a été étudiée entre 750^{circ}C et 1300^{circ}C en utilisant deux techniques : la déformation par compression à vitesse imposée et la flexion 4 points. La courbe... more
La transition fragile-ductile du polytype 4H du carbure de silicium a été étudiée entre 750^{circ}C et 1300^{circ}C en utilisant deux techniques : la déformation par compression à vitesse imposée et la flexion 4 points. La courbe représentant les variations de la contrainte d'écoulement en fonction de la température présente une cassure à une température Tc, associée à un changement de
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... 0.4 Table 1. Stacking sequence of a few common SiC polytypes 3. Dislocations in SiC Dislocations in non-cubic SiC polytypes lie on the basal (0001) plane and, in the undissociated state, have a Burgers vector, b, equal to - &lt;... more
... 0.4 Table 1. Stacking sequence of a few common SiC polytypes 3. Dislocations in SiC Dislocations in non-cubic SiC polytypes lie on the basal (0001) plane and, in the undissociated state, have a Burgers vector, b, equal to - &lt; 1120 &gt; ; in the cubic polytype, the dislocations lie ...
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... been reported.4*7-9 It has been suggested that the density of atomic-scale surface ... by Matsunami and co-workers4*12 whereby the growth of the 3C polytype on low-tilt-angle ... For smaller angles (lower step density and wider... more
... been reported.4*7-9 It has been suggested that the density of atomic-scale surface ... by Matsunami and co-workers4*12 whereby the growth of the 3C polytype on low-tilt-angle ... For smaller angles (lower step density and wider terraces between steps), there is a higher probability ...
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Dislocation velocities in semiconductors depend strongly on the concentration of electrically active impurities, at temperatures in which the intrinsic lattice resistance is rate controlling. The effect is explained in terms of deep... more
Dislocation velocities in semiconductors depend strongly on the concentration of electrically active impurities, at temperatures in which the intrinsic lattice resistance is rate controlling. The effect is explained in terms of deep acceptor and donor levels in the band gap associated with kinks. Doping affects yield stress, indentation hardness and the pattern of plastic flow and cracking around indentations. New insight has been gained about the nature of the plastic zone under an indenter, and the difference in hardness of (111) and (III) faces of GaAs has been explained.
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The geometric configuration of intersecting twin bands has been considered in the past in the context of dislocation mechanisms and deformation behavior. It is generally found that a twin band is an effective barrier to the propagation of... more
The geometric configuration of intersecting twin bands has been considered in the past in the context of dislocation mechanisms and deformation behavior. It is generally found that a twin band is an effective barrier to the propagation of another, noncoplanar, twin band. However, under conditions of sufficiently high local stress twin intersections are possible, subject to conditions of continuity. The problem of intersecting twins has gained renewed interest with the recent hot-indention experiments in silicon. The deformation microstructure consists of twin bands and planar ribbons of hexagonal Si radiating from the area of the indent. Although at high pressures silicon forms in several different crystal structures, only the diamond-cubic structure is stable at atmospheric pressure. Thus the diamond-hexagonal structure that forms during hot indentation of single crystals is a metastable modification. Recent research established its crystallography by means of high-resolution elect...
Research Interests: Electron Microscopy, High Pressure, Data Analysis, Transmission Electron Microscopy, Crystal structure, and 10 moreHigh Resolution Transmission Electron Microscopy, Activation Energy, Atmospheric Pressure, Dislocations, Iron, Temperature Dependence, Order-Disorder, X ray diffraction, Single Crystal, and Microstructures
The electron-beam-induced current (EBIC) mode of scanning electron microscopy was employed to investigate the nucleation and development of stacking faults (SFs) during forward high current stress operation of 4H-SiC p-i-n diodes. The... more
The electron-beam-induced current (EBIC) mode of scanning electron microscopy was employed to investigate the nucleation and development of stacking faults (SFs) during forward high current stress operation of 4H-SiC p-i-n diodes. The EBIC technique is shown to be a valuable tool for the visualization and analysis of mobile and immobile partial dislocations bounding the SFs and their recombination activity. Both Si and C core partial dislocations exhibit similar EBIC contrast. It is shown that threading edge dislocations can be one source of SF generation leading to the degradation of p-i-n diodes.
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... Xian-Jie Ning,+ Nicolas Huvey,* and Pirouz Pirouz' ... 20). In an indentation test, however, the configuration of the rosette patterns on the indented surface?' and elastic analy-sis of the resolved shear stresses in the... more
... Xian-Jie Ning,+ Nicolas Huvey,* and Pirouz Pirouz' ... 20). In an indentation test, however, the configuration of the rosette patterns on the indented surface?' and elastic analy-sis of the resolved shear stresses in the plastic zone of the indentation? ...
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ABSTRACT The nucleation and growth of deformation twins are discussed, assuming that twinning occurs via the double-cross-slip mechanism first postulated by Pirouz for twinning in silicon. The dislocation energetics in this model are... more
ABSTRACT The nucleation and growth of deformation twins are discussed, assuming that twinning occurs via the double-cross-slip mechanism first postulated by Pirouz for twinning in silicon. The dislocation energetics in this model are described in detail. In all cases, dislocation dissociation occurs and gives rise to a stationary partial and a twinning partial; twin growth involves the twinning partial undergoing double cross-slip. We discuss three specific geometries: firstly, the dissociation of a perfect dislocation into three collinear partials of equal Burgers vectors, which describes basal twinning in sapphire and twinning in bcc metals; secondly, the dissociation of a perfect dislocation into two collinear partials with different Burgers vectors, which describes rhombohedral twinning in sapphire; thirdly, the dissociation of a perfect dislocation into two non-collinear Shockley partials, which is used to describe twinning in silicon. Finally, the double-cross-slip mechanism readily explains the formation of emissary dislocations at the twinmatrix interface of deformation twins in bcc metals.
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ABSTRACT Structure images of a compound semiconductor, CdTe, have been obtained in the [011] projection using 120 kV transmission electron microscopy. Image spots, corresponding to adjacent columns of cadmium and tellurium atoms, have... more
ABSTRACT Structure images of a compound semiconductor, CdTe, have been obtained in the [011] projection using 120 kV transmission electron microscopy. Image spots, corresponding to adjacent columns of cadmium and tellurium atoms, have been resolved in the experimental images, the observed separation being slightly larger than the true resolved atomic separation of 1.62 Å. Also, an intensity difference between the spots corresponding to the two atomic species is noted. Image calculations based on the Bloch-wave formulation indicate that the experimental images can be adequately simulated with 13 beams contributing to the image formation. The possibility of distinguishing between the columns of cadmium and tellurium atoms in the experimental images is examined, with instrumental and specimen parameters used as variables. It is found that the intensity difference is a sensitive function of lens defocus and specimen thickness, and identification of atomic species in the image is possible only when the experimental parameters are accurately known. The image behaviour is more complex than that for elemental semiconductors. The relevance of these findings to the lattice imaging of other compound semiconductors is discussed.
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The {100} and (110) faces of n-type GaSb and the {110) face of n-type GaAs have been indented at room temperature and 200°C, and the plastic zone around the microindents has been investigated by transmission electron microscopy. In both... more
The {100} and (110) faces of n-type GaSb and the {110) face of n-type GaAs have been indented at room temperature and 200°C, and the plastic zone around the microindents has been investigated by transmission electron microscopy. In both materials, indentation rosettes with approximate twofold symmetry form around the indents. In general, the rosettes consist of dislocations and microtwins. The
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ABSTRACT Eight intrinsic exciton spectra with band gaps ranging from 3.03 to 2.672 eV are found due to embedded in 4H SiC homoepitaxial films grown in hot-wall reactors. A correlation is found between the appearance of these embedded... more
ABSTRACT Eight intrinsic exciton spectra with band gaps ranging from 3.03 to 2.672 eV are found due to embedded in 4H SiC homoepitaxial films grown in hot-wall reactors. A correlation is found between the appearance of these embedded spectra and reduced lifetime as well as electron microscopic evidence for stacking faults.
Transmission electron microscopy and dislocation etch pit techniques were used to examine the dislocation structure around elevated-temperature indentations on {111} and {001} surfaces of 9·4 mol% Y2O3-stabilized cubic ZrO2 single... more
Transmission electron microscopy and dislocation etch pit techniques were used to examine the dislocation structure around elevated-temperature indentations on {111} and {001} surfaces of 9·4 mol% Y2O3-stabilized cubic ZrO2 single crystals. The activated slip systems were identified and the geometry of the plastic zone characterized. The effect of the plastic zone on radial crack formation was also examined.
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The interface between Cu and faceted particles of a cubic Al2O3 phase in an internally oxidized CuAl alloy was studied by HRTEM. Image simulations indicate that the Al2O3 precipitates have a highly disordered spinel-type structure. The... more
The interface between Cu and faceted particles of a cubic Al2O3 phase in an internally oxidized CuAl alloy was studied by HRTEM. Image simulations indicate that the Al2O3 precipitates have a highly disordered spinel-type structure. The precipitates grow by ledge migration and possess internal defects, mainly coherent twin boundaries and stacking faults. At the Cu/Al2O3 interface, two orientation relationships were