Peculiarities of REBCO Films Growth on Single Crystalline Substrates

2011 ◽  
Vol 1367 ◽  
Author(s):  
Constantin G. Tretiatchenko ◽  
Victor S. Flis ◽  
Vassily L. Svetchnikov ◽  
Volodymyr M. Pan
Keyword(s):  
Film Growth ◽  
Lattice Mismatch ◽  
Subgrain Size ◽  
High Temperature Superconductors ◽  
Finite Size ◽  
Rotational Relaxation ◽  
Layered Perovskite ◽  
Layered Perovskite Structure ◽  
Edge Dislocations ◽  
Equilibrium Effect

ABSTRACTWe suggest a model of mismatched interface and calculate its energy in order to describe formation of threading edge dislocations by the mechanism of rotational relaxation of interface stresses. The model takes into account strongly layered perovskite structure of high-temperature superconductors. We have shown that rotational relaxation occurs due to finite size of clusters and to non-equilibrium effect of the film growth. We have predicted the subgrain size and the expected rotation of domains depending on the lattice mismatch. The computed values are consistent with the observed YBCO film nanostructure.

Model of Subgrain Structure Formation in HTS Cuprates and Ferropnictides

2012 ◽  
Vol 1434 ◽  
Author(s):  
Constantin G. Tretiatchenko ◽  
Vassily L. Svetchnikov ◽  
Harold Wiesmann
Keyword(s):  
Film Growth ◽  
Lattice Mismatch ◽  
Subgrain Size ◽  
Finite Size ◽  
Interface Energy ◽  
Rotational Relaxation ◽  
Subgrain Structure ◽  
Relaxation Of Stresses ◽  
Validity Range ◽  
Edge Dislocations

ABSTRACTWe have modified the model of rotational relaxation of stresses at mismatched interface by taking into account elastic strains of the growing film. This extended the model validity range to a wider class of compounds including pnictides. The model describes formation of low angle boundaries consisting of threading edge dislocations. Calculated interface energy shows that rotational relaxation occurs due to finite size of clusters and to non-equilibrium effect of the film growth. Subgrain size and expected angle of domain rotation depending on the lattice mismatch have been estimated. Unusual effect of increasing angle between the film subgrains at reduction of the deposition rate is predicted. The computed parameters of subgrains are consistent with the observed film nanostructure.

Simulation of the Organization of Heteroepitaxial Monolayer Islands Under Anisotropic Conditions

2004 ◽  
Vol 854 ◽  
Author(s):  
Gajendra Pandey ◽  
Robert V. Kukta
Keyword(s):  
Point Defects ◽  
Surface Stress ◽  
Lattice Mismatch ◽  
Finite Size ◽  
Source Model ◽  
Crystalline Material ◽  
Elastic Fields ◽  
High Anisotropy ◽  
Degree Of Anisotropy ◽  
Hexagonal Arrays

ABSTRACTThis paper addresses the effect of anisotropy on the organization of epitaxial islands deposited on a substrate. Focus is on in-plane anisotropies in surface stress and lattice mismatch between the film and substrate materials. Starting from a configuration where island sizes and position are random, evolution towards equilibrium through mass transport via condensation/evaporation is simulated. The effect of the degree of anisotropy is investigated. An efficient numerical method is obtained by reducing a model of square monolayer islands of finite size to point defects that interact through their elastic fields. Models for both the kinetics and energetics of the system are obtained by this reduction. It is found that the point source model is accurate for island separations larger than about 3 times the width of an island. Under isotropic conditions islands tend to form into hexagonal arrays, and as there is no preferred orientation of these arrays, defects analogous to grain boundaries in a crystalline material tend to arise. With anisotropy islands tend to align in particular directions. This is found to enhance organization in cases of modest anisotropy and cause islands to form into zigzagged lines in cases of high anisotropy.

The mechanism of sputter-induced epitaxy modification in YBCO (001) films grown on MgO (001) substrates

1998 ◽  
Vol 13 (12) ◽  
pp. 3378-3388
Author(s):  
Y. Huang ◽  
B. V. Vuchic ◽  
M. Carmody ◽  
P. M. Baldo ◽  
K. L. Merkle ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Film Growth ◽  
Ybco Film ◽  
Lattice Mismatch ◽  
Substrate Surface ◽  
Oriented Growth ◽  
Orientation Change ◽  
Large Lattice Mismatch ◽  
Major Factors ◽  
Hot Filament

The sputter-induced epitaxy change of in-plane orientation occurring in YBa2Cu3O7-x (001) thin films grown on MgO (001) substrates by pulsed organo-metallic beam epitaxy (POMBE) is investigated by a series of film growth and characterization experiments, including RBS and TEM. The factors influencing the orientation change are systematically studied. The experimental results suggest that the substrate surface morphology change caused by the ion sputtering and the Ar ion implantation in the substrate surface layer are not the major factors that affect the orientation change. Instead, the implantation of W ions, which come from the hot filament of the ion gun, and the initial Ba deposition layer in the YBCO film growth play the most important roles in controlling the epitaxy orientation change. Microstructure studies show that a BaxMg1-xO buffer layer is formed on top of the sputtered substrate surface due to Ba diffusion into the W implanted layer. It is believed that the formation of this buffer layer relieves the large lattice mismatch and changes the YBCO film from the 45° oriented growth to the 0° oriented growth.

Void and Dislocation Microstructure Development in Heteroepitaxial Film Growth

1995 ◽  
Vol 399 ◽  
Author(s):  
Richard W. Smith ◽  
David J. Srolovitz
Keyword(s):  
Thin Films ◽  
Molecular Dynamics ◽  
Film Growth ◽  
Lattice Misfit ◽  
Two Dimensional ◽  
Microstructure Development ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
Film Substrate ◽  
Edge Dislocations

ABSTRACTTwo dimensional, non-equilibrium molecular dynamics simulations have been performed to examine the microstructures of both homoepitaxial and heteroepitaxial thin films grown on single crystal substrates. The principal microstructural features to develop within these films are small voids and edge dislocations. Voids form near the surface of the growing film as surface depressions between microcolumns pinch off to become closed volumes. These voids often form in such a way as to introduce dislocations into the crystal with their cores positioned within the voids. Dislocations are also formed during heteroepitaxy at the interface between the substrate and film. These dislocations tend to be mobile. When voids are present in the film and when the lattice misfit is low, dislocations tend to be trapped in the voids or pulled toward them due to dislocation image interactions. Once attached to voids, dislocations are effectively pinned there. When voids are absent or when the misfit is high, dislocations are restricted to the film-substrate interface. In the case of heteroepitaxy, dislocations are found to relieve either tensile or compressive misfit stresses. Misfit stresses may also be accommodated, to some extent, merely by the free volume of the voids themselves.

Electrical Characterization and Microstructures of Y2O3-Doped Bi4Ti3O12 Thin Films

2013 ◽  
Vol 591 ◽  
pp. 208-211
Author(s):  
Min Chen ◽  
J. Liu ◽  
X.A. Mei
Keyword(s):  
Thin Films ◽  
Electrical Characterization ◽  
Rf Magnetron Sputtering ◽  
Layered Perovskite ◽  
Random Orientation ◽  
Large Shift ◽  
Si Substrates ◽  
Layered Perovskite Structure ◽  
Lower Temperature ◽  
Curie Temperature Tc

Y2O3-doped bismuth titanate (Bi4-xYxTi3O12: BYT) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. Y-doping into BIT caused a large shift of the Curie temperature ( TC ) from 675 °C to lower temperature and a improvement in dielectric property. The experimental results indicated that Y doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BYT film with x=0.75 were 28 μC/cm2 and 65 kV/cm, respectively.

Sn-based Group-IV Semiconductors on Si: New Infrared Materials and New Templates for Mismatched Epitaxy

2005 ◽  
Vol 891 ◽  
Author(s):  
John Tolle ◽  
Radek Roucka ◽  
Vijay D'Costa ◽  
Jose Menendez ◽  
Andrew Chizmeshya ◽  
...  
Keyword(s):  
Band Gap ◽  
Buffer Layer ◽  
Lattice Mismatch ◽  
Group Iv ◽  
Buffer Layers ◽  
Direct Band Gap ◽  
Group Iv Semiconductors ◽  
Direct Band ◽  
Infrared Materials ◽  
Edge Dislocations

ABSTRACTWe report growth and properties of GeSn and SiGeSn alloys on Si (100). These materials are prepared using a novel CVD approach based on reactions of Si-Ge hydrides and SnD4. High quality GeSn films with Sn contents up to 20%, and strain free microstructures have been obtained. The lattice mismatch between the films and Si is relieved by Lomer edge dislocations located at the interface. This material is of interest due to the predicted cross-over to a direct gap semiconductor for moderate Sn concentrations. We find that the direct band gap, and, consequently, the main absorption edge, shifts monotonically to lower energies as the Sn concentration is increased. The compositional dependence of the direct band gap shows a strong bowing, such that the direct band gap is reduced to 0.4 eV (from 0.8 eV for pure Ge) for a concentration of 14% Sn. The ternary SiGeSn alloy has been grown for the first time on GeSn buffer layers. This material opens up entirely new opportunities for strain and band gap engineering using group-IV materials via decoupling of strain and composition. Our SiGeSn layers have lattice constants above and below that of pure Ge, and depending on the thickness and composition of the underlying buffer layer they can be grown relaxed, with compressive, or with tensile strain. In addition to acting as a buffer layer for the growth of SiGeSn, we have found that GeSn can act as a template for the subsequent growth of a variety of materials, including III-V semiconductors.

Structural Defects and Their Relationship to Nucleation of Gan Thin Films

1996 ◽  
Vol 423 ◽  
Author(s):  
Weida Gian ◽  
Marek Skowronski ◽  
Greg S. Rohrer
Keyword(s):  
Film Growth ◽  
Three Dimensional ◽  
Scanning Force Microscopy ◽  
Columnar Structure ◽  
Layer Growth ◽  
Buffer Layers ◽  
Structural Defects ◽  
Layer By Layer ◽  
Extended Defects ◽  
Edge Dislocations

AbstractMicrostructure and extended defects in α-GaN films grown by organometallic vapor phase epitaxy on sapphire substrates using low temperature AIN (or GaN) buffer layers have been studied using transmission electron microscopy. The types and distribution of extended defects were correlated with the film growth mode and the layer nucleation mechanism which was characterized by scanning force microscopy. The nature of the extended defects was directly related to the initial three-dimensional growth. It was found that inhomogeneous nucleation leads to a grain-like structure in the buffer; the GaN films then have a columnar structure with a high density of straight edge dislocations at grain boundaries which are less likely to be suppressed by common annihilation mechanisms. Layer-by-layer growth proceeds in many individual islands which is evidenced by the observation of hexagonal growth hillocks. Each growth hillock has an open-core screw dislocation at its center which emits monolayer-height spiral steps.

Nonisothermal reaction kinetics and preparation of ferroelectric strontium bismuth niobate with a layered perovskite structure

2004 ◽  
Vol 19 (10) ◽  
pp. 2956-2963 ◽  
Author(s):  
Chung-Hsin Lu ◽  
Wei-Tse Hsu ◽  
Jiun-Ting Lee
Keyword(s):  
Reaction Kinetics ◽  
Formation Mechanism ◽  
Integral Method ◽  
Correlation Coefficients ◽  
Differential Method ◽  
Layered Perovskite ◽  
Heating Rates ◽  
Integral Methods ◽  
Diffusion Controlled ◽  
Layered Perovskite Structure

Ferroelectric layered perovskite SrBi2Nb2O9 has been successfully prepared through a new process using BiNbO4 as a precursor. The SrBi2Nb2O9 formation mechanism was investigated using a nonisothermal analysis method at constant heating rates. The weight loss recorded in thermal analysis under different heating rates was analogized to the reaction conversion. A combination of the differential and integral methods was introduced to solve the reaction mechanisms. Analysis using the differential method revealed that two kinds of diffusion-controlled models have higher linear correlation coefficients than other models. Based on the integral method principle, a new integral equation combining the Arrhenius equation and the Lobatto approximation was derived in this study. The established equation significantly simplified the conventional calculation process and improved the accuracy for predicting the reaction models. Analysis using the integral method corroborated that the SrBi2Nb2O9 formation mechanism is governed by Jander's diffusion controlled model, and the activation energy was calculated to be 192.1 kJ/mol. The proposed methods and the derived equations can be further applied to other solid-state-reaction systems to elucidate their reaction kinetics and estimate the related kinetic parameters.

Defect Structure and Oxide-ion Conduction in (La, Sr)2NiO4+δ with Layered Perovskite Structure

2020 ◽  
Vol 49 (9) ◽  
pp. 1071-1074
Author(s):  
Naoto Kitamura ◽  
Kakeru Ishizaki ◽  
Naoya Ishida ◽  
Yasushi Idemoto
Keyword(s):  
Defect Structure ◽  
Perovskite Structure ◽  
Layered Perovskite ◽  
Ion Conduction ◽  
Layered Perovskite Structure ◽  
Oxide Ion Conduction ◽  
Oxide Ion
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