Enabling coherent BaZrO3 nanorods/YBa2Cu3O7-x interface through dynamic lattice enlargement in vertical epitaxy of BaZrO3/YBa2Cu3O7-x nanocomposites

2022 ◽  
Author(s):  
Judy Z Wu ◽  
Victor Ogunjimi ◽  
Mary Ann Sebastian ◽  
Di Zhang ◽  
Jie Jian ◽  
...  
Keyword(s):  
Defect Formation ◽  
Lattice Mismatch ◽  
Single Layer ◽  
Nanocomposite Films ◽  
Force Density ◽  
Elemental Distribution ◽  
Pinning Force ◽  
One Dimensional ◽  
Transmission Electron ◽  
Axis Elongation

Abstract One-dimensional c-axis-aligned BaZrO3 (BZO) nanorods are regarded as strong one-dimensional artificial pinning centers (1D-APCs) in BZO-doped YaBa2Cu3O7-x (BZO/YBCO) nanocomposite films. However, a microstructure analysis has revealed a defective, oxygen-deficient YBCO column around the BZO 1D-APCs due to the large lattice mismatch of ~7.7% between the BZO (3a=1.26 nm) and YBCO (c=1.17 nm), which has been blamed for the reduced pinning efficiency of BZO 1D-APCs. Herein, we report a dynamic lattice enlargement approach on the tensile strained YBCO lattice during the BZO 1D-APCs growth to induce c-axis elongation of the YBCO lattice up to 1.26 nm near the BZO 1D-APC/YBCO interface via Ca/Cu substitution on single Cu-O planes of YBCO, which prevents the interfacial defect formation by reducing the BZO/YBCO lattice mismatch to ~1.4%. Specifically, this is achieved by inserting thin Ca0.3Y0.7Ba2Cu3O7-x (CaY-123) spacers as the Ca reservoir in 2-6 vol.% BZO/YBCO nanocomposite multilayer (ML) films. A defect-free, coherent BZO 1D-APC/YBCO interface is confirmed in transmission electron microscopy and elemental distribution analyses. Excitingly, up to five-fold enhancement of Jc (B) at magnetic field B=9.0 T//c-axis and 65-77 K was obtained in the ML samples as compared to their BZO/YBCO single-layer (SL) counterpart’s. This has led to a record high pinning force density Fp together with significantly enhanced Bmax at which Fp reaches its maximum value Fp,max for BZO 1D-APCs at B//c-axis. At 65 K, the Fp,max ~158 GN/m3 and Bmax ~ 8.0 T for the 6% BZO/YBCO ML samples represent a significant enhancement over Fp,max ~36.1 GN/m3 and Bmax ~ 5.0 T for the 6% BZO/YBCO SL counterparts. This result not only illustrates the critical importance of a coherent BZO 1D-APC/YBCO interface in the pinning efficiency, but also provides a facile scheme to achieve such an interface to restore the pristine pinning efficiency of the BZO 1D-APCs.

Microstructure and Current Transport Properties of YBa2Cu3O7-x/(Ba0.05, Sr0.95)TiO3 Multiple-Layer Thin Films

2003 ◽  
Vol 795 ◽  
Author(s):  
Y. Luo ◽  
R. A. Hughes ◽  
J. S. Preston ◽  
G. A. Botton
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Electrical Properties ◽  
Lattice Mismatch ◽  
Single Layer ◽  
Nanocomposite Films ◽  
Mismatch Strain ◽  
Multiple Layer ◽  
Transmission Electron

ABSTRACTYBa2Cu3O7-x (YBCO) films grown by pulsed laser deposition (PLD) on (100) LaAlO3 (LAO) substrates show a strong thickness dependence on the electrical properties. For example, for films in excess of 0.3 μm, the critical current density decreases with increasing thickness. In contrast, nano-composite films consisting of a series of multiple layers of YBa2Cu3O7-x and (Ba0.05, Sr0.95)TiO3 (BSTO) thin films having a total thickness of 5 μm show improved electrical properties. In order to understand this phenomenon, a detailed microstructural characterization has been undertaken. Transmission electron microscopy (TEM) observations show that cracks, stacking faults, c-║ crystals and secondary phase precipitates are present on the single-layer films, while a high-quality microstructure is observed for the nanocomposite multiple-layer films although defects at YBCO/BSTO interface are still present. In addition, nanocomposite films have a reduced surface roughness. In this complex microstructure, the YBCO/BSTO interfaces and the lattice mismatch strain play a crucial role in controlling the nature of the defects and stability of phases. In order to understand the role of the BSTO layer has on the microstructure, the interfacial mismatch strain and defects are analyzed by high-resolution transmission electron microscopy (HRTEM) in combination with the Moiré fringe technique.

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.

Condition Dependences of Extended Defect Formation in 4H-SiC by Ion-Implantation/Activation-Anneal Process

2010 ◽  
Vol 645-648 ◽  
pp. 323-326 ◽  
Author(s):  
Masahiro Nagano ◽  
Hidekazu Tsuchida ◽  
Takuma Suzuki ◽  
Tetsuo Hatakeyama ◽  
Junji Senzaki ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Defect Formation ◽  
Single Layer ◽  
Annealing Treatment ◽  
Annealing Process ◽  
Extended Defect ◽  
Aluminum Ions ◽  
Transmission Electron ◽  
Activation Annealing ◽  
Nitrogen Phosphorus

Condition dependences of defect formation in 4H-SiC epilayer induced by the implantation/annealing process were investigated using synchrotron reflection X-ray topography and transmission electron microscopy. Nitrogen, phosphorus or aluminum ions were implanted in the 4H-SiC epilayers and then activation annealing was performed. To compare the implantation/annealing process, a sample receiving only the annealing treatment without the implantation was also performed. Two different crucibles (conventional and improved) were used in the annealing process. The formation of single layer Shockley-type stacking faults near the surface was found to have no ion-implantation condition or crucible dependence. The formation of BPD half-loops and the glide of pre-existing BPDs showed clear dependence on the crucibles.

Bound Exciton Energies, Biaxial Strains, and Defect Microstructures in GaN/AlN/6H-SiC(0001) Heterostructures

1996 ◽  
Vol 449 ◽  
Author(s):  
W. G. Perry ◽  
T. Zheleva ◽  
K. J. Linthicum ◽  
M. D. Bremser ◽  
R. F. Davis ◽  
...  
Keyword(s):  
Defect Formation ◽  
Lattice Mismatch ◽  
Compressive Strain ◽  
Lattice Parameter ◽  
Buffer Layers ◽  
Film Stress ◽  
Thermal Expansion Coefficients ◽  
Transmission Electron ◽  
Defect Microstructures

ABSTRACTBiaxial strains resulting from mismatches in thermal expansion coefficients and lattice parameters in 22 GaN films grown on A1N buffer layers previously deposited on vicinal and on-axis 6H-SiC(0001) substrates were measured via changes in the c-axis lattice parameter (c). Six of the films were in compression, indicating the residual strain due to lattice mismatch was not relieved. A Poisson's ratio of v=0.18 was calculated. The bound exciton energy (EBx) was a linear function of these strains. The shift in EBx with film stress was 23 meV/GPa. The role of the SiC off-axis tilt was investigated for GaN films grown concurrently on the vicinal and on-axis 6H-SiC substrates. Marked variations in EBx and c were observed, with a maximum shift of ΔEBx = 15 meV and Δc = 0.0042 Å. Threading dislocations densities of ~1010/cm2 and ~108/cm2 were determined for GaN films grown on vicinal and on-axis SiC, respectively. A 0.9% residual compressive strain at the GaN/AIN interface was observed by high resolution transmission electron microscopy (HRTEM). It is proposed that the on-axis SiC substrate does not offer a sufficient density of steps for defect formation to relieve the lattice mismatch between GaN and A1N and A1N and SiC.

Studies of Morphological Instability and Dislocation Formation in Heteroepitaxial Si1−xGex Thin Films Via Controlled Annealing Experiments

1996 ◽  
Vol 440 ◽  
Author(s):  
Cengiz S. Ozkan ◽  
William D. Nix ◽  
Huajian Gao
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Defect Formation ◽  
Lattice Mismatch ◽  
Hydrogen Atmosphere ◽  
Surface Roughening ◽  
Silicon Substrates ◽  
Transmission Electron ◽  
Annealing Experiments

AbstractHeteroepitaxial Si1−x Gex thin films deposited on silicon substrates exhibit surface roughening via surface diffusion under the effect of a compressive stress which is caused by a lattice mismatch. In these films, surface roughening takes place in the form of ridges aligned along either <100> or <110> directions depending on the film thickness and composition. In this paper, we compare the relaxation behaviour of capped and uncapped heteroepitaxial Si1−xGex thin films containing 22% Ge, with surface roughening being inhibited in films with a capping layer. Films with 50 nm thickness were deposited on bare silicon substrates in a LPCVD reactor. Annealing experiments were conducted in a Hydrogen atmosphere in the reactor chamber. Transmission electron microscopy and atomic force microscopy have been used to study the surface morphology and microstructure of these films. XRD measurements were conducted to determine the amount of relaxation in these films. In-situ transmission electron microscopy/annealing experiments have been performed on uncapped Si1−x Gex/Si structures to study the dynamics of surface roughening and defect formation in a vacuum ambient. Finally, we compare surface morphologies and defects in samples subjected to annealing in vacuum and H2 ambients.

Transmission Electron Microscopy studies of the vacancy ordering in YSI2-X thin films

1991 ◽  
Vol 49 ◽  
pp. 562-563
Author(s):  
F.-R. Chen ◽  
T. L. Lee ◽  
L. J. Chen
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Thin Films ◽  
Diffraction Pattern ◽  
Annealing Temperature ◽  
Lattice Mismatch ◽  
Si Substrate ◽  
Metal Thin Films ◽  
Transmission Electron ◽  
Vacancy Ordering

YSi2-x thin films were grown by depositing the yttrium metal thin films on (111)Si substrate followed by a rapid thermal annealing (RTA) at 450 to 1100°C. The x value of the YSi2-x films ranges from 0 to 0.3. The (0001) plane of the YSi2-x films have an ideal zero lattice mismatch relative to (111)Si surface lattice. The YSi2 has the hexagonal AlB2 crystal structure. The orientation relationship with Si was determined from the diffraction pattern shown in figure 1(a) to be and . The diffraction pattern in figure 1(a) was taken from a specimen annealed at 500°C for 15 second. As the annealing temperature was increased to 600°C, superlattice diffraction spots appear at position as seen in figure 1(b) which may be due to vacancy ordering in the YSi2-x films. The ordered vacancies in YSi2-x form a mesh in Si plane suggested by a LEED experiment.

Influence of MBE Growth Conditions on Dislocation Densities of GaAs/Ge Epilayers Grown on Silicon Substrates

1985 ◽  
Vol 43 ◽  
pp. 364-365
Author(s):  
K.M. Hones ◽  
P. Sheldon ◽  
B.G. Yacobi ◽  
A. Mason
Keyword(s):  
High Efficiency ◽  
Lattice Mismatch ◽  
Low Cost ◽  
Growth Conditions ◽  
Nonradiative Recombination ◽  
Device Structure ◽  
Si Substrates ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Dislocation Type

There is increasing interest in growing epitaxial GaAs on Si substrates. Such a device structure would allow low-cost substrates to be used for high-efficiency cascade- junction solar cells. However, high-defect densities may result from the large lattice mismatch (∼4%) between the GaAs epilayer and the silicon substrate. These defects can act as nonradiative recombination centers that can degrade the optical and electrical properties of the epitaxially grown GaAs. For this reason, it is important to optimize epilayer growth conditions in order to minimize resulting dislocation densities. The purpose of this paper is to provide an indication of the quality of the epitaxially grown GaAs layers by using transmission electron microscopy (TEM) to examine dislocation type and density as a function of various growth conditions. In this study an intermediate Ge layer was used to avoid nucleation difficulties observed for GaAs growth directly on Si substrates. GaAs/Ge epilayers were grown by molecular beam epitaxy (MBE) on Si substrates in a manner similar to that described previously.

Structural analysis of a Σ5 grain boundary in YBa2Cu3O7δ

1993 ◽  
Vol 51 ◽  
pp. 942-943
Author(s):  
J.-Y. Wang ◽  
Y. Zhu ◽  
A.H. King ◽  
M. Suenaga
Keyword(s):  
Grain Boundary ◽  
Lattice Mismatch ◽  
Weak Link ◽  
Coincidence Site Lattice ◽  
Large Angle ◽  
Dislocation Core ◽  
Superconducting Order Parameter ◽  
Outstanding Problem ◽  
Transmission Electron

One outstanding problem in YBa2Cu3O7−δ superconductors is the weak link behavior of grain boundaries, especially boundaries with a large-angle misorientation. Increasing evidence shows that lattice mismatch at the boundaries contributes to variations in oxygen and cation concentrations at the boundaries, while the strain field surrounding a dislocation core at the boundary suppresses the superconducting order parameter. Thus, understanding the structure of the grain boundary and the grain boundary dislocations (which describe the topology of the boundary) is essential in elucidating the superconducting characteristics of boundaries. Here, we discuss our study of the structure of a Σ5 grain boundary by transmission electron microscopy. The characterization of the structure of the boundary was based on the coincidence site lattice (CSL) model.Fig.l shows two-beam images of the grain boundary near the projection. An array of grain boundary dislocations, with spacings of about 30nm, is clearly visible in Fig. 1(a), but invisible in Fig. 1(b).

X-ray mapping without STEM

1994 ◽  
Vol 52 ◽  
pp. 508-509
Author(s):  
Judith M. Brock ◽  
Max T. Otten
Keyword(s):  
Life Science ◽  
Materials Science ◽  
Chemical Elements ◽  
Full Description ◽  
Scanning System ◽  
Elemental Distribution ◽  
X Ray ◽  
Transmission Electron ◽  
Distribution Of Elements ◽  
Made In

A knowledge of the distribution of chemical elements in a specimen is often highly useful. In materials science specimens features such as grain boundaries and precipitates generally force a certain order on mental distribution, so that a single profile away from the boundary or precipitate gives a full description of all relevant data. No such simplicity can be assumed in life science specimens, where elements can occur various combinations and in different concentrations in tissue. In the latter case a two-dimensional elemental-distribution image is required to describe the material adequately. X-ray mapping provides such of the distribution of elements.The big disadvantage of x-ray mapping hitherto has been one requirement: the transmission electron microscope must have the scanning function. In cases where the STEM functionality – to record scanning images using a variety of STEM detectors – is not used, but only x-ray mapping is intended, a significant investment must still be made in the scanning system: electronics that drive the beam, detectors for generating the scanning images, and monitors for displaying and recording the images.

3D Observation of Elemental Distribution of Si-Device using a Dedicated FIB/STEM System

2005 ◽  
Author(s):  
T. Yaguchi ◽  
M. Konno ◽  
T. Kamino ◽  
M. Ogasawara ◽  
K. Kaji ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Three Dimensional ◽  
Elemental Distribution ◽  
Multivariate Statistical ◽  
X Ray ◽  
Sample Rotation ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Elemental Maps

Abstract A technique for preparation of a pillar shaped sample and its multi-directional observation of the sample using a focused ion beam (FIB) / scanning transmission electron microscopy (STEM) system has been developed. The system employs an FIB/STEM compatible sample rotation holder with a specially designed rotation mechanism, which allows the sample to be rotated 360 degrees [1-3]. This technique was used for the three dimensional (3D) elemental mapping of a contact plug of a Si device in 90 nm technology. A specimen containing a contact plug was shaped to a pillar sample with a cross section of 200 nm x 200 nm and a 5 um length. Elemental analysis was performed with a 200 kV HD-2300 STEM equipped with the EDAX genesis Energy dispersive X-ray spectroscopy (EDX) system. Spectrum imaging combined with multivariate statistical analysis (MSA) [4, 5] was used to enhance the weak X-ray signals of the doped area, which contain a low concentration of As-K. The distributions of elements, especially the dopant As, were successfully enhanced by MSA. The elemental maps were .. reconstructed from the maps.

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