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.

Structural Studies Of (ZnSe/FeSe) Superlattices By Transmission Electron Microscopy

1991 ◽  
Vol 238 ◽  
Author(s):  
K. Park ◽  
L. Salamanca-Riba ◽  
B. T. Jonker
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Buffer Layer ◽  
Molecular Beam ◽  
Misfit Strain ◽  
Structural Studies ◽  
Ordered Structure ◽  
Chemical Ordering ◽  
Gaas Substrates ◽  
Transmission Electron

ABSTRACTThe structural properties of (ZnSe/FeSe) superlattices, grown with and without a ZnSe buffer layer on (001) G a As substrates by molecular beam epitaxy, have been studied by transmission electron microscopy. High quality (ZnSe/FeSe) superlattices are obtained when grown on a ZnSe buffer layer on (001) GaAs substrates. In contrast, nominal (ZnSe/FeSe) superlattices grown directly on (001) GaAs substrates without a buffer layer showed evidence for intermixing of the layers in the superlattice indicating that the superlattice is unstable. We observed a disordered structure and an ordered structure in the resulting Zn1−xFexSe solid solution. The ordered structure corresponds to chemical ordering of Zn and Fe atoms along the < 100 > and < 110 > directions. We have studied the effect of misfit strain in the (ZnSe/FeSe) superlattices on the film quality.

Layer Tilt and Relaxation in InGaAs/GaAs Graded Buffer Layers

1995 ◽  
Vol 379 ◽  
Author(s):  
K.M. Matney ◽  
J.W. Eldredge ◽  
M.S. Goorsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Buffer Layer ◽  
Cross Section ◽  
Mole Fraction ◽  
Molecular Beam ◽  
Reciprocal Space ◽  
Buffer Layers ◽  
Gaas Substrates ◽  
Transmission Electron

ABSTRACTWe investigated the effect of substrate inclination and direction on the structural properties of an InGaAs linearly compositionally graded buffer layer with a AlGaAs/InGaAs superlattice grown by molecular beam epitaxy on 2° offcut GaAs substrates. Reciprocal space maps were used to determine the relaxation and tilt of the buffer layer and superlattice with respect to each other and to the substrate. From (004) reciprocal space maps, a linear relationship between tilt and In mole fraction was observed for the buffer layer. This tilt was greatly reduced near the top of the buffer which was found to be completely strained. Interestingly, the tilt along a <110> direction was greater than that observed along the miscut axis. This may be due to the miscut axis not being parallel to a low index plane. Reciprocal space maps of asymmetric diffraction planes were used to determine the relaxation of the buffer layer as a function of In mole fraction. Along a <110> direction in which no tilt was seen in the (004), the majority of the buffer layer was found to be completely relaxed. However, the top of the buffer layer was found to be completely strained, corresponding to a denuded zone observed in cross section transmission electron microscopy.

Microstructure of SrTiO3 Thin Films as Single Layer and Incorporated in Yba2Cu3O7-x/SrTiO3 Multilayers

1995 ◽  
Vol 401 ◽  
Author(s):  
L. Ryen ◽  
E. Olssoni ◽  
L. D. Madsen ◽  
C. N. L. Johnson ◽  
X. Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Lattice Mismatch ◽  
Single Layer ◽  
Transmission Electron ◽  
Tilt Boundaries ◽  
Interfacial Dislocations ◽  
The Individual ◽  
Film Substrate

AbstractEpitaxial single layer (001) SrTiO3 films and an epitaxial Yba2Cu3O7-x/SrTiO3 multilayer were dc and rf sputtered on (110)rhombohedral LaAIO3 substrates. The microstructure of the films was characterised using transmission electron microscopy. The single layer SrTiO3 films exhibited different columnar morphologies. The column boundaries were due to the lattice mismatch between film and substrate. The boundaries were associated with interfacial dislocations at the film/substrate interface, where the dislocations relaxed the strain in the a, b plane. The columns consisted of individual subgrains. These subgrains were misoriented with respect to each other, with different in-plane orientations and different tilts of the (001) planes. The subgrain boundaries were antiphase or tilt boundaries.The individual layers of the Yba2Cu3O7-x/SrTiO3 multilayer were relatively uniform. A distortion of the SrTiO3 unit cell of 0.9% in the ‘001’ direction and a Sr/Ti ratio of 0.62±0.04 was observed, both in correspondence with the single layer SrTiO3 films. Areas with different tilt of the (001)-planes were also present, within each individual SrTiO3 layer.

Interfacial Structure of BaRuO3 Thin Films Grown On (111) SrTiO3

2000 ◽  
Vol 654 ◽  
Author(s):  
W. Tian ◽  
M. K. Lee ◽  
C. B. Eom ◽  
X. Q. Pan
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Intermediate Layer ◽  
Interfacial Structure ◽  
Initial Growth ◽  
Growth Modes ◽  
Transmission Electron ◽  
Quantitative Image ◽  
Film Substrate

AbstractBaRuO3 thin films were grown on (111) SrTiO3substrate by 90° off-axis rf-sputtering. Transmission electron microscopy studies revealed that the films consist of the metastable 4H hexagonal polymorph of BaRuO3 along with few defects. The films are c-axis oriented, single crystalline with the in-plane orientation relationship with respect to the SrTiO3substrate of [112 0] BaRuO3 // [110] SrTiO3. High-resolution transmission electron microscopy (HRTEM) studies of the film-substrate interface revealed the existence of a thin intermediate layer of the 9R hexagonal polymorph of BaRuO3 between the (111) SrTiO3 substrate and the 4H film. The formation mechanism for the intermediate layer is not fully understood though. Through the combination of HRTEM and quantitative image simulations, the atomic structure of the interface between the 9R intermediate layer and the underneath (111) SrTiO3 was constructed. Three initial growth modes were observed, each of them adopting the local continuity of the oxygen octahedral sublattice across the interface.

Characterization of spray-pyrolized superconducting YBaCuO thin films on single-crystal MgO by transmission electron microscopy

1990 ◽  
Vol 5 (8) ◽  
pp. 1605-1611 ◽  
Author(s):  
S. J. Golden ◽  
H. Isotalo ◽  
M. Lanham ◽  
J. Mayer ◽  
F. F. Lange ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Film Thickness ◽  
Single Crystal ◽  
Processing Parameters ◽  
Transmission Electron ◽  
Film Substrate ◽  
Mgo Substrate

Superconducting YBaCuO thin films have been fabricated on single-crystal MgO by the spray-pyrolysis of nitrate precursors. The effects on the superconductive behavior of processing parameters such as time and temperature of heat treatment and film thickness were investigated. The superconductive behavior was found to be strongly dependent on film thickness. Films of thickness 1 μm were found to have a Tc of 67 K while thinner films showed appreciably degraded properties. Transmission electron microscopy studies have shown that the heat treatments necessary for the formation of the superconductive phase (for example, 950 °C for 30 min) also cause a substantial degree of film-substrate interdiffusion. Diffusion distances for Cu in the MgO substrate and Mg in the film were found to be sufficient to explain the degradation of the superconductive behavior in films of thickness 0.5 μm and 0.2 μm. From the concentration profiles obtained by EDS analysis diffusion coefficients at 950 °C for Mg into the YBaCuO thin film and for Cu into the MgO substrate were evaluated as 3 × 10−19 m2/s and 1 × 10−17 m2/s, respectively.

TEM Analyses Of Cu-Ta And Cu-Tan Interfaces

1999 ◽  
Vol 564 ◽  
Author(s):  
J. Y. Phillip Wang ◽  
Hong Zhang ◽  
Imran Hashim ◽  
Girish Dixit ◽  
Fusen Chen
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Thermal Treatment ◽  
Amorphous Layer ◽  
Energy Dispersion ◽  
X Ray ◽  
Barrier Layers ◽  
Transmission Electron ◽  
Sharp Interfaces

AbstractThis paper reports an extensive interfacial study of Cu deposited on Ta and TaN barrier layers. It has been reported that the Cu/Ta interface develops a uniform and thin amorphous layer at the interface upon thermal treatment[l]. However, our high resolution transmission electron microscopy (HRTEM) analysis shows atomically sharp interfaces for all conditions without any amorphous layer at the interfaces, especially for the ones which underwent one hour annealing at 400°C and 500°C. The “amorphization” effect is only observed if the Cu/Ta TEM specimen is exposed to oxygen. It exists usually at the thinner regions of the TEM specimen or if the specimen is left in air for > 24 hours. Energy dispersion x-ray (EDX) analysis of the “amorphized” region shows that it is a mixture of Cu, Ta, and O.

Tem Assessment of Defects in (CdHg)Te Heterostructures

1990 ◽  
Vol 216 ◽  
Author(s):  
S.G. Lawson-Jack ◽  
I.P. Jones ◽  
D.J. Williams ◽  
M.G. Astles
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Buffer Layer ◽  
High Density ◽  
Misfit Dislocations ◽  
Cross Sectional ◽  
Burgers Vector ◽  
Density Of Dislocations ◽  
Transmission Electron ◽  
Interfacial Plane

ABSTRACTTransmission electron microscopy has been used to assess the defect contents of the various layers and interfaces in (CdHg) Te heterostructures. Examination of cross sectional specimens of these materials suggests that the density of misfit dislocations at the interfaces is related to the layer thicknesses, and that the high density of dislocations which are generated at the GaAs/CdTe interface are effectively prevented from penetrating into the CdHgTe epilayer by a 3um thick buffer layer. The majority of the dislocations in the layers were found to have a Burgers vector b = a/2<110> and either lie approximately parallel or inclined at an angle of ∼ 60° to the interfacial plane.

Cross-Sectional TEM Study Of Phase Separation In Reaction Of Ni-Ta Films With GaAs

1985 ◽  
Vol 54 ◽  
Author(s):  
A. Lahav ◽  
M. Eizenberg ◽  
Y. Komem
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
Phase Separation ◽  
Gaas Substrate ◽  
Auger Spectroscopy ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
X Ray ◽  
Transmission Electron

ABSTRACTThe reaction between Ni60Ta40 amorphous alloy and (001) GaAs was studied by cross-sectional transmission electron microscopy, Auger spectroscopy, and x-ray diffraction. At 400°C formation of Ni GaAs at the interface with GaAs was observed. After heat treatment at 600°C in vacuum a layered structure of TaAs/NiGa/GaAs has been formed. The NiGa layer has epitaxial relations to the GaAs substrate. The vertical phase separation can be explained by opposite diffusion directions of nickel and arsenic atoms.

A Study of the Defect Structure in GaAS1−xPx/GaAs AS x<0.25

1993 ◽  
Vol 317 ◽  
Author(s):  
G. Aragon ◽  
M.J. De Castro ◽  
S.I. Molina ◽  
Y. Gonzalez ◽  
L. Gonzalez ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Defect Structure ◽  
Gaas Substrate ◽  
Molecular Beam ◽  
Atomic Layer ◽  
Multiple Cracks ◽  
Transmission Electron ◽  
Phosphorous Content

ABSTRACTThe defect structure of GaAsP layer grown by Atomic Layer Molecular Beam Epitaxy on (001) GaAs substrate has been studied by Transmission Electron Microscopy. The phosphorous content and the epilayer thickness have been changed below 25% and 1μm respectively. Three kinds of defect structure have been found: a) α-δ fringes at the interface for coherent epilayer, b) Misfit dislocation for thin epilayers and c) Multiple cracks normal to the interface and parallel to one <110> direction for thick epilayers.

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