Double Axis X-Ray Diffractometry Analysis of the Homoepitaxial Interface Between Substrate and Buffer Layer

1990 ◽  
Vol 208 ◽  
Author(s):  
G. Stephan Green ◽  
Brian K. Tanner ◽  
Philip Kightley
Keyword(s):  
Buffer Layer ◽  
Interfacial Layer ◽  
Gaas Substrate ◽  
Interface Layer ◽  
Lattice Parameter ◽  
Good Match ◽  
Low Contrast ◽  
X Ray ◽  
Gaas Substrates ◽  
Transmission Electron

ABSTRACTHigh resolution double axis X-ray diffractometry has been undertaken on InGaAs/AlGaAs strained layer epitaxial systems on (001) GaAs substrates. A clear set of fringes has been identified which arises due to the presence of an imperfect layer at the interface between the GaAs substrate and the undoped GaAs epitaxial buffer layer. The period corresponds to the Pendellosung period for the whole epitaxial layer stack. These fringes have very low contrast and are not present in all specimens studied. Detailed simulations have been undertaken assuming a thin interfacial layer of GaAs with a different lattice parameter to the substrate. The system is equivalent to a Bragg case X-ray interferometer. Fringe amplitude is found to vary linearly with interface layer thickness and increases with mismatch of this layer. A good match between experiment and simulation was obtained for a 1 nm layer mismatched by 3000 ppm. The presence of such a layer, probably GaCxAsl-x has been confirmed by transmission electron microscopy. We show that highly sh'rained layers of this thickness between layers over 1 micron in thickness can lead to splitting of high intensity layer peaks, giving rise to possible misinterpretation of data.

Epitaxial tilt of partially relaxed InGaAs layers grown on (100) GaAs substrates

1992 ◽  
Vol 70 (10-11) ◽  
pp. 838-842
Author(s):  
P. Maigné ◽  
A. P. Roth ◽  
C. Desruisseaux ◽  
D. Coulas
Keyword(s):  
Residual Strain ◽  
Gaas Substrate ◽  
Strain Relaxation ◽  
Azimuthal Angle ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Monoclinic Symmetry ◽  
X Ray ◽  
Mismatch Strain ◽  
Gaas Substrates

The structural properties of partially relaxed InxGa1−xAs layers grown on (100) GaAs substrates have been investigated, using high-resolution X-ray diffraction, in order to better understand the mechanisms responsible for the relaxation of the mismatch strain. From symmetric [400] reflections recorded as functions of the azimuthal angle [Formula: see text], the (100) InGaAs planes are found to be tilted with respect to the (100) GaAs substrate planes. The tilt magnitude is first seen to decrease then to increase with layer thickness. The direction of the tilt changes from [01-1] to [00-1] in the range of thickness investigated. From [422] asymmetric reflections, the average in-plane lattice parameter, the indium composition as well as the percentage of relaxation can be measured. Our values for relaxation are in qualitative agreement with the Dodson and Tsao model of strain relaxation (Appl. Phys. Lett. 51, 1710 (1987)). In addition, our data show an anisotropy in residual strain along <011> directions. This anisotropy increases with the amount of strain relieved and changes the crystal symmetry of the cell from tetragonal to monoclinic. This monoclinic symmetry can be characterized by an angle β that measures the angle between 90° and the inner angles of the new crystallographic cell. As for the anisotropy in residual strain, |3 increases with the amount of strain relieved. Correlations between tilt magnitude and tilt direction with the formation of 60° type dislocations are discussed.

Ordered Structures of Zn1-xFexSe Epilayers Grown on GaAs Substrates with ZnSe Buffer Layers

1994 ◽  
Vol 340 ◽  
Author(s):  
H.-Y. Wei ◽  
D. Prasad Beesabathina ◽  
L. Salamanca-Riba ◽  
B. T. Jonker
Keyword(s):  
Buffer Layer ◽  
Hexagonal Structure ◽  
Buffer Layers ◽  
Ordered Structure ◽  
Rough Interface ◽  
Triangular Form ◽  
Ordered Structures ◽  
X Ray ◽  
Gaas Substrates ◽  
Transmission Electron

ABSTRACTWe observed the coexistence of two types of ordered structures, Cu3Au and CuPt, in Zn0.4Fe0.6Se epilayers grown on ZnSe buffer layers on (001) GaAs substrates by transmission electron microscopy. In addition, the Cu3Au ordered structure exists with a multi-faceted domain shape. Energy dispersive x-ray spectra from these domains showed higher Fe concentration than in the disordered matrix. However, in Zn0.5Fe0.5Se epilayers, we only observed CuAu-I ordered multi-faceted domains. The samples with relatively high Fe concentration (x ≈0.6) also showed domains of FeSe with a hexagonal structure with triangular form coexisting with Cu3Au ordered domains. Strain-induced interdiffusion takes place between the buffer layer and the epilayer as evidenced by a rough interface between the alloy and the buffer layer.

A Tem study of Epitaxial FE/AG and MN/AG Superlattices

1989 ◽  
Vol 160 ◽  
Author(s):  
S. Nahm ◽  
L. Salamanca — Riba ◽  
B. T. Jonker ◽  
G. A. Prinz
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Buffer Layer ◽  
Seed Layer ◽  
Gaas Substrate ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
Strain Modulation ◽  
Film Substrate ◽  
Sharp Interfaces

AbstractWe have studied the epitaxial growth and structural properities of single crystal Fe/Ag and Mn/Ag superlattices grown on (001) GaAs substrates using transmission electron microscopy. A buffer layer of Ag (001) was grown on a 5 monolayer Fe seed layer on the (001) GaAs substrate before the growth of the superlattice to obtain good quality films. For some samples an intermediate buffer layer of ZnSe was used, as well. Both Fe/Ag and Mn/Ag superlattices with a Ag buffer layer show very sharp interfaces. The densities of dislocations in the film and the buffer layer are the same suggesting that the dislocations originate at the film/substrate interface. We have observed evidence for a strain modulation of ≈ 8 Å in the Mn layer for thick (≈ 22 Å) Mn layers in the superlattice samples but not in samples with a thin Mn layer.

Magnetic Anisotropy in Electrodeposited CO Films and spin-valves on Gaas Substrates

1999 ◽  
Vol 562 ◽  
Author(s):  
K. Attenborough ◽  
M. Cerisier ◽  
H. Boeve ◽  
J. De Boeck ◽  
G. Borghs ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Buffer Layer ◽  
Structural Properties ◽  
Easy Axis ◽  
Spin Valve ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cu Films ◽  
Gaas Substrates ◽  
Unique Spin

ABSTRACTWe have studied the magnetic and structural properties of thin electrodeposited Co and Cu layers grown directly onto (100) n-GaAs and have investigated the influence of a buffer layer. A dominant fourfold anisotropy with a uniaxial contribution is observed in 10 nm Co electrodeposited films on GaAs. An easy axis is observed in the [001] GaAs direction with two hard axes of differing coercivities parallel to the [011] and [011] directions. For thicker films the easy axes in the [001] direction becomes less pronounced and the fourfold anisotropy becomes less dominant. Co films of similar thicknesses deposited onto an electrodeposited Cu buffer layer were nearly isotropic. From X-ray diffraction 21 nm Co layers on GaAs were found to be hcp with the c-axis tending to be in the plane of the film. The anisotropy is ascribed to the Co/GaAs interface and is held responsible for the unique spin-valve properties seen recently in electrodeposited Co/Cu films.

scholarly journals Grazing-incidence X-ray diffraction of single GaAs nanowires at locations defined by focused ion beams

2013 ◽  
Vol 46 (4) ◽  
pp. 887-892 ◽  
Author(s):  
Genziana Bussone ◽  
Rüdiger Schott ◽  
Andreas Biermanns ◽  
Anton Davydok ◽  
Dirk Reuter ◽  
...  
Keyword(s):  
Gaas Substrate ◽  
Lattice Spacing ◽  
Molecular Beam ◽  
Grazing Incidence ◽  
Lattice Parameter ◽  
Ion Beams ◽  
Focused Ion Beams ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gaas Nanowires

Grazing-incidence X-ray diffraction measurements on single GaAs nanowires (NWs) grown on a (111)-oriented GaAs substrate by molecular beam epitaxy are reported. The positions of the NWs are intentionally determined by a direct implantation of Au with focused ion beams. This controlled arrangement in combination with a nanofocused X-ray beam allows the in-plane lattice parameter of single NWs to be probed, which is not possible for randomly grown NWs. Reciprocal space maps were collected at different heights along the NW to investigate the crystal structure. Simultaneously, substrate areas with different distances from the Au-implantation spots below the NWs were probed. Around the NWs, the data revealed a 0.4% decrease in the lattice spacing in the substrate compared with the expected unstrained value. This suggests the presence of a compressed region due to Au implantation.

Defect Reduction in Cd1-xZnxTe Epilayers on GaAs Substrates

1994 ◽  
Vol 299 ◽  
Author(s):  
Saket Chadda ◽  
Kevin Malloy ◽  
John Reno
Keyword(s):  
Threading Dislocation ◽  
Full Width ◽  
X Ray Diffraction ◽  
Defect Reduction ◽  
X Ray ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
Threading Dislocation Density ◽  
Optimum Period ◽  
Bulk Alloys

AbstractCd0.91Zn0.09Te/CdTe multilayers of various period thicknesses were inserted into Cd0.955Zn0.045Te bulk alloys grown on (001) GaAs. The net strain of the multilayer on the underlying Cd0.955Zn0.045Te was designed to be zero. X-ray diffraction full width at half maximum (FWHM) was used as a means to optimize the period thickness of the multilayer. Transmission electron microscopy of the optimum period thickness samples demonstrated four orders of magnitude decrease in the threading dislocation density. Mechanism of bending by equi-strained multilayers is discussed.

Structural Properties of InAs/AlSb Superlattices

1995 ◽  
Vol 379 ◽  
Author(s):  
B. Jenichen ◽  
H. Neuroth ◽  
B. Brar ◽  
H. Kroemer
Keyword(s):  
Buffer Layer ◽  
Peak Shift ◽  
Lattice Parameter ◽  
Structural Quality ◽  
Inhomogeneous Deformation ◽  
X Ray ◽  
Peak Broadening ◽  
Short Period ◽  
Intensity Ratios ◽  
Highly Correlated

ABSTRACTShort-period (InAs)6/(AlSb)6 superlattices (SL) with AlAs-like and InSb-like interfaces (IF) grown on a relaxed AlSb buffer layer are studied by X-ray reflectivity and diffractometry measurements. Reflectivity measurements reveal average IF roughnesses between 0.6 and 1.0 nm. Measurements of the diffuse scattering show that the roughness is highly correlated from layer to layer. Triple crystal area scans illustrate that the inhomogeneous deformation of the buffer layer leads to a certain symmetric peak broadening. In the case of AlAs-like IFs an additional broadening of the SL peaks reveals lattice parameter gradients over the superlattice. This asymmetric peak broadening may be attributed to a further relaxation of the superlattice, which is inhomogeneous with depth. The diffusion of As into the AlSb layers leads to a peak shift and modifies the intensity ratios of the different satellite reflections. The best structural quality is achieved for superlattices with InSb-like IFs.

Thermal Treatment Induced Dislocation Bundles in Gaas Substrates Studied by Scanning Infrared Polariscopy, Visible-Light Interferometry, Transmission Electron Microscopy, Makyoh and X-Ray Topography

2000 ◽  
Vol 6 (S2) ◽  
pp. 1104-1105
Author(s):  
P. Mock
Keyword(s):  
Plastic Deformation ◽  
Technical Problem ◽  
Sample Holder ◽  
Mbe Growth ◽  
X Ray ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
Topographic Survey ◽  
Key Factor ◽  
Peripheral Areas

It is well known that heat treatment induced plastic deformation of GaAs substrates is a key factor that reduces the yield of electronic devices in manufacturing processes on an industrial scale. Our recent X-ray topographic survey showed that a quite common, radiatively heated, non In-bonded sample holder design can cause severe plastic deformation in two-inch diameter GaAs (001) substrates when they are heated up to about 650 °C in a molecular beam epitaxy (MBE) growth chamber. Unintentional plastic deformation occurred for all three investigated MBE machines, which were of different make, but we overcame the technical problem by modifications to the sample holder of a user built MBE machine. At present, however, there is no theoretical model available that can satisfactorily describe the experimental observations including the spatial distribution of the majority of the dislocation bundles.The plastic deformation up to about 98 % is realised by bundles of dislocations which start at the sample edges around the four <100> peripheral areas,

InAs Quantum Dots Grown on an AlGaAsSb Strain-Relief Buffer

2000 ◽  
Vol 642 ◽  
Author(s):  
A.L. Gray ◽  
L. R. Dawson ◽  
Y. Lin ◽  
A. Stintz ◽  
Y.-C. Xin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Cross Section ◽  
Gaas Substrate ◽  
Buffer Layers ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Strain Relief ◽  
Inas Quantum Dots ◽  
X Ray ◽  
Transmission Electron

ABSTRACTAn In(Ga)As-based self-assembled quantum dot laser test structure grown on strain-relief Al0.5Ga0.5As1-ySby strain-relief buffer layers (0≤y ≤ 0.24) on a GaAs substrate is investigated in an effort to increase dot size and therefore extend the emission wavelength over conventional InAs quantum dots on GaAs platforms. Cross-section transmission electron microscopy, and high-resolution x-ray diffraction are used to monitor the dislocation filtering process and morphology in the buffer layers. Results show that the buffer layers act as an efficient dislocation filter by drastically reducing threading dislocations, thus providing a relaxed, low dislocation, compositionally modulated Al0.5Ga0.5Sb0.24As0.76 substrate for large (500Å height x 300Å width) defect -free InAs quantum dots. Photoluminescence shows a ground-state emission of the InAs quantum dots at 1.45 μm.

The microstructure and stoichiometry of pyrite FeS2−x

1992 ◽  
Vol 7 (7) ◽  
pp. 1829-1838 ◽  
Author(s):  
S. Fiechter ◽  
M. Birkholz ◽  
A. Hartmann ◽  
P. Dulski ◽  
M. Giersig ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Lattice Parameter ◽  
Population Parameter ◽  
Microscope Examination ◽  
Density Measurements ◽  
X Ray ◽  
Transmission Electron ◽  
Structural Nature ◽  
Synthetic Crystals

Both natural and synthetic crystals of pyrite, FeS2−x, have been analyzed chemically and examined structurally by transmission electron microscopy and x-ray powder diffraction. Chemical analysis and density measurements have shown the synthetic crystals, grown at 850 K, are frequently deficient in sulfur, with a composition of FeS2−x with x ⋚ 0.15. From a refinement of the pyrite structure using the integral intensities of the x-ray powder pattern, a variation in the sulfur population parameter was obtained ranging from 0.87(2) to 1.03(3). A correlation according to Vegard's rule between the population factor and the lattice parameter a0 has been proven. Transmission electron microscope examination revealed that the crystals did not contain a significant population of disorder defects which may account for this apparent sulfur deficit. Therefore the nonstoichiometry in pyrite has to be interpreted in terms of S vacancies which can be understood as the tendency of the material to reduce the high anion content in the unit cell. The structural nature of nonstoichiometric pyrite is discussed in relationship to other related disulfides.

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