scholarly journals An Investigation on the Lattice Site Location of the Excess Arsenic Atoms in GaAs layers Grown by Low Temperature Molecular Beam Epitaxy

1991 ◽  
Vol 241 ◽  
Author(s):  
Kin Man Yu ◽  
Z. Liliental-Weber
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Lattice Site ◽  
Tetrahedral Site ◽  
Site Location ◽  
X Ray ◽  
Ion Channeling ◽  
Transmission Electron ◽  
A Site ◽  
Substrate Temperatures

ABSTRACTWe have measured the excess As atoms present in GaAs layers grown by molecular beam epitaxy at low substrate temperatures using particle induced x-ray emission technique. The amount of excess As atoms in layers grown by MBE at 2000C were found to be ∼4×1020 cm−2. Subsequent annealing of the layers under As overpressure at 600'C did not result in any substantial As loss. However, transmission electron microscopy revealed that As precipitates (2- 5nm in diameter) were present in the annealed layers. The lattice location of the excess As atoms in the as grown layers was investigated by ion channeling methods. Angular scans were performed in the <110> axis of the crystal. Our resutls strongly suggest that a, arge fraction of these excess As atoms are located in an interstitial position close to an As row. These As “intersitials” are located at a site slightly displaced from the tetrahedral site in a diamond cubic lattice. No interstitial As signal is observed in the annealed layers.

Double Periodicity Formation in EuTe/PbTe Superlattices

1995 ◽  
Vol 399 ◽  
Author(s):  
M. Shima ◽  
L. Salamanca-Riba ◽  
G. Springholz ◽  
G. Bauer
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Short Period ◽  
Short Period Superlattices

ABSTRACTMolecular beam epitaxy was used to grow EuTe(x)/PbTe(y) short period superlattices with x=1-4 EuTe(111) monolayers alternating with y≈3x PbTe monolayers. The superlattices were characterized by transmission electron microscopy and high resolution x-ray diffraction. Regions with double periodicity were observed coexisting with areas of nominal periodicity. The sample with x=3.5 and y=9, for example, contains regions with double periodicity of x=7 and y=17. X-ray diffraction measurements confirm the formation of the double periodicity in these samples by the appearance of weak satellites in between the satellites of the nominal periodicity. The double periodicity in the superlattice is believed to result from interdiffusion during the growth. A model for this process is presented.

Optimization of synthesis of the solid solution, Pb(Zr1–xTix)O3 on a single substrate using a high-throughput modified molecular-beam epitaxy technique

2009 ◽  
Vol 24 (1) ◽  
pp. 164-172 ◽  
Author(s):  
P.S. Anderson ◽  
S. Guerin ◽  
B.E. Hayden ◽  
Y. Han ◽  
M. Pasha ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
High Throughput ◽  
Molecular Beam ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
Single Substrate ◽  
Transmission Electron ◽  
Substrate Temperatures

Synthesis of Pb(Zr1–xTix)O3 (PZT) on a single substrate using a high-throughput molecular-beam epitaxy technique was demonstrated. In situ synthesis of crystalline PZT at elevated substrate temperatures could not be achieved, as reevaporation of Pb (PbO) occurred and the partial pressure of O2 was insufficient to prevent formation of a PbPtx phase during deposition. Instead, ex situ postdeposition annealing was performed on PZT deposited at room temperature. Dense single phase PZT was prepared with a compositional range of 0.1 > x > 0.9, for film thicknesses up to 800 nm. Transmission electron microscopy revealed the grain size increased from 50 nm to ∼0.5 μm with increasing Zr-concentration and became more columnar. Raman, x-ray diffraction, and scanning electron microscopy/energy dispersive spectroscopy results revealed a morphotropic phase boundary between rhombohedral and tetragonal phases occurred at x ∼0.4 rather than at x = 0.47 in bulk ceramics. This was attributed to clamping arising from mismatch in thermal expansion between the film and substrate.

Site occupations in L12 ordered alloys by axial electron channeling microanalysis

1986 ◽  
Vol 44 ◽  
pp. 704-705
Author(s):  
J. Bentley
Keyword(s):  
Lattice Site ◽  
Site Occupancy ◽  
Zone Axis ◽  
Site Location ◽  
X Ray Diffraction ◽  
Alloy Development ◽  
X Ray ◽  
Ion Channeling ◽  
Ordered Alloys ◽  
Lattice Planes

Lattice site location of alloying additions to A3B-type ordered alloys with the L12 structure is important for alloy development, but ion channeling and X-ray diffraction techniques require single crystal specimens. The ALCHEMI technique is applicable to polycrystalline specimens but provides only qualitative results on the site occupancy in L12 A3B alloys. Quantitative analysis by standard planar channeling ALCHEMI is complicated by the absence of lattice planes containing only B atoms. Since certain zone axes, including <001> and <111>, contain columns of A atoms well separated from columns of B atoms, the ALCHEMI method has been extended to use zone axis channeling conditions. Further, the procedure has been simplified to use spectra recorded from two orientations - an appropriate channeling zone axis and a “random” non-channeling condition typically 2-5° from the zone. The concentration CX of element X on the B sites is given by Cx = {R(X/A) - 1}/{R(B/A) - 1}, where R(X/A) = (NX/NA)zone/(NX/NA)random, ete., and NX, NA, NB are the characteristic X-ray intensities of elements X, A, and B.

Reciprocal Space X-Ray Mapping and Transmission Electron Microscopic Studies of Coincided δ-Inas and As-Cluster Superlattices in Gaas Films Grown by Molecular-Beam Epitaxy at Low Temperature

1999 ◽  
Vol 583 ◽  
Author(s):  
V. V. Chaldyshev ◽  
N. A. Bert ◽  
N. N. Faleev ◽  
Yu. G. Musikhin ◽  
A. E. Kunitsyn ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Reciprocal Space ◽  
Growth Surface ◽  
Electron Microscopic ◽  
Extended Defect ◽  
X Ray ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Interference Picture

AbstractInAs/GaAs superlattices with thin (0.5–1 monolayer) δ-InAs insertions were grown by molecular beam epitaxy at low (150–200°C) temperature. The as-grown samples contained up to 1020 cm−3 arsenic antisite defects. Transmission electron microscopic study revealed no extended defect and showed that the real thickness of δ-InAs insertions is 3–4 monolayers. This thickness seems to be due to short-range roughness of the growth surface. Low diffuse scattering and extended interference picture were observed for such superlattices by x-ray diffraction study. Superlattices of two-dimensional cluster sheets were produced by annealing of the δ-InAs/GaAs superlattices at 500–600°C. Precipitation of excess arsenic at InAs δ-layers was found to be accompanied by enhanced In-Ga intermixing, roughening the InAs δ-layers, and smoothing the x-ray interference picture. No evidence for any self-ordering in the system of nanoscale As clusters was revealed using x-ray mapping in reciprocal space.

scholarly journals Структурная характеризация короткопериодной сверхрешетки на основе гетероструктуры CdF-=SUB=-2-=/SUB=-/CaF-=SUB=-2-=/SUB=-/Si(111) методами просвечивающей электронной микроскопии и рентгеновской дифрактометрии

2021 ◽  
Vol 47 (15) ◽  
pp. 3
Author(s):  
Л.М. Сорокин ◽  
Р.Н. Кютт ◽  
В.В. Ратников ◽  
А.Е. Калмыков
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Fragment Size ◽  
Diffraction Curve ◽  
X Ray ◽  
Transmission Electron ◽  
Short Period ◽  
Lateral Inhomogeneity

A detailed study of the structure of a short-period superlattice based on alternating layers of cadmium and calcium fluorides, grown by molecular beam epitaxy on a Si (111) substrate, by transmission electron microscopy and X-ray diffractometry, has been carried out. It was found that the superlattice is in a pseudomorphic state, and a lateral inhomogeneity with a fragment size of 10 - 40 nm was found. The reason for the broadening of the main and satellite peaks of the SL on the (111) diffraction curve has been clarified.

Growth by molecular beam epitaxy of (rare-earth group V element)/III-V semiconductor heterostructures

1995 ◽  
Vol 10 (8) ◽  
pp. 1942-1952 ◽  
Author(s):  
A. Guivarc'h ◽  
A. Le Corre ◽  
P. Auvray ◽  
B. Guenais ◽  
J. Caulet ◽  
...  
Keyword(s):  
Rare Earth ◽  
Molecular Beam Epitaxy ◽  
Photoelectron Spectroscopy ◽  
Molecular Beam ◽  
High Energy ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
Group V ◽  
X Ray ◽  
Transmission Electron

This paper deals with the growth by molecular beam epitaxy of semimetallic (rare-earth group V element) compounds on III-V semiconductors. Results are presented, first on the Er-Ga-As and Er-Ga-Sb ternary phase diagrams, second on the lattice-mismatched ErAs/GaAs (δa ≈ +1.6%), YbAs/GaAs (δa/a = +0.8%), and ErSb/GaSb (δa/a ≈ +0.2%) heterostructures, and third on the lattice-matched Sc0.3Er0.7As/GaAs and Sc0.2Yb0.8As/GaAs systems (δa/a < 0.05%). Finally the growth of YbSb2 on GaSb(001) is reported. The studies made in situ by reflection high-energy electron diffraction (RHEED) and x-ray photoelectron diffraction and ex situ by x-ray diffraction, transmission electron microscopy, He+ Rutherford backscattering, and photoelectron spectroscopy are presented. We discuss the atomic registry of the epitaxial layers with respect to the substrates, the appearance of a mosaic effect in lattice-mismatched structures, and the optical and electrical properties of the semimetallic films. The problems encountered for III-V overgrowth on these compounds (lack of wetting and symmetry-related defects) are commented on, and we underline the interest of compounds as YbSb2 which avoid the appearance of inversion defects in the GaSb overlayers.

InP Layers Grown by Molecular Beam Epitaxy at Low Substrate Temperature

1991 ◽  
Vol 241 ◽  
Author(s):  
K. Xie ◽  
C. R. Wie ◽  
G. W. Wicks
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Double Crystal ◽  
X Ray ◽  
Hall Effect Measurements ◽  
Phosphorus Source ◽  
Substrate Temperatures

ABSTRACTInP layers were grown on semi-insulating InP wafer by molecular beam epitaxy (MBE) at low substrate temperatures (<200° C), using solid phosphorus source. We use x-ray diffraction, double crystal x-ray rocking curve, Auger electron spectroscopy, and temperature-dependent Van der Pauw and Hall effect measurements to characterize the as-grown and annealed InP layers. It is found that the InP layer is in poly-crystal state with excess P over 7 at%. The layers became single crystal after annealing above 400°C. The resistivity of the InP layer decreased from 60 Ωcm for an as-grown sample to 0.82 Ωcm after 400°C RTA annealing. The different role of excess P as compared to the role played by excess As in LT-GaAs is discussed based on the P properties.

Incorporation of Excess Arsenic in GaAs and AlGaAs Epilayers Grown at Low Substrate Temperatures by Molecular Beam Epitaxy

1991 ◽  
Vol 241 ◽  
Author(s):  
M. R. Melloch ◽  
N. Otsuka ◽  
K. Mahalingam ◽  
A. C. Warrew ◽  
J. M. Woodall ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Activation Energy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Volume Fraction ◽  
Transmission Electron ◽  
Si Doped ◽  
Substrate Temperatures ◽  
Inverse Substrate

ABSTRACTExcess arsenic can be incorporated in GaAs and AIGaAs epilayers by growing at low substrate temperatures (LT-GaAs and LT-AIGaAs) by molecular beam epitaxy (MBE). Upon annealing these epilayers, the excess As precipitates forming GaAs:As and AIGaAs:As. Using transmission electron microscopy (TEM), we have measured the densities and sizes of the As precipitates and thereby determined the amount of excess As incorporated in these epilayers. The volume fraction of excess As as a function of inverse substrate growth temperature follows an Arrhenius-type behavior with an activation energy of 0.87 eV. The sizes of the As precipitates increase and the densities decrease with increase anneal temperatures; for Si-doped GaAs:As this results in n-type material when the densities become small enough that the depletion regions around the As precipitates no longer overlap. Also investigated is the formation of As precipitates at GaAs/AIGaAs heterojunctions and superlattices, and our attempts to tailor the As precipitate distribution.

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