Atomic-Scale Insights on Large-Misfit Heterointerfaces in LSMO/MgO/c-Al2O3

Understanding the interfaces in heterostructures at an atomic scale is crucial in enabling the possibility to manipulate underlying functional properties in correlated materials. This work presents a detailed study on the atomic structures of heterogeneous interfaces in La0.7Sr0.3MnO3 (LSMO) film grown epitaxially on c-Al2O3 (0001) with a buffer layer of MgO. Using aberration-corrected scanning transmission electron microscopy, we detected nucleation of periodic misfit dislocations at the interfaces of the large misfit systems of LSMO/MgO and MgO/c-Al2O3 following the domain matching epitaxy paradigm. It was experimentally observed that the dislocations terminate with 4/5 lattice planes at the LSMO/MgO interface and with 12/13 lattice planes at the MgO/c-Al2O3 interface. This is consistent with theoretical predictions. Using the atomic-resolution image data analysis approach to generate atomic bond length maps, we investigated the atomic displacement in the LSMO/MgO and MgO/c-Al2O3 systems. Minimal presence of residual strain was shown at the respective interface due to strain relaxation following misfit dislocation formation. Further, based on electron energy-loss spectroscopy analysis, we confirmed an interfacial interdiffusion within two monolayers at both LSMO/MgO and MgO/c-Al2O3 interfaces. In essence, misfit dislocation configurations of the LSMO/MgO/c-Al2O3 system have been thoroughly investigated to understand atomic-scale insights on atomic structure and interfacial chemistry in these large misfit systems.

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The Roles of Stress, Geometry and Orientation on Misfit Dislocations Kinetics and Energetics in Epitaxial Strained Layers.

MRS Proceedings ◽

10.1557/proc-239-379 ◽

1991 ◽

Vol 239 ◽

Cited By ~ 3

Author(s):

R. Hull ◽

J. C. Bean ◽

F. Ross ◽

D. Bahnck ◽

L. J. Pencolas

Keyword(s):

Misfit Dislocation ◽

Lattice Mismatch ◽

Strain Relaxation ◽

Misfit Dislocations ◽

Slip Systems ◽

Strained Layers ◽

Burgers Vector ◽

Partial Dislocations ◽

Strain Stress ◽

Kinetics Of

ABSTRACTThe geometries, microstructures, energetics and kinetics of misfit dislocations as functions of surface orientation and the magnitude of strain/stress are investigated experimentally and theoretically. Examples are drawn from (100), (110) and (111) surfaces and from the GexSi1–x/Si and InxGa1–x/GaAs systems. It is shown that the misfit dislocation geometries and microstructures at lattice mismatch stresses < - 1GPa may in general be predicted by operation of the minimum magnitude Burgers vector slipping on the widest spaced planes. At stresses of the order several GPa, however, new dislocation systems may become operative with either modified Burgers vectors or slip systems. Dissociation of totál misfit dislocations into partial dislocations is found to play a crucial role in strain relaxation, on surfaces other than (100) under compressive stress.

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Strain Relaxation Mechanisms in He+-Implanted and Annealed Si1−xGex Layers on Si(001) Substrates

MRS Proceedings ◽

10.1557/proc-686-a1.6 ◽

2001 ◽

Vol 686 ◽

Author(s):

S.H. Christiansen ◽

P.M. Mooney ◽

J.O. Chu ◽

A. Grill

Keyword(s):

Misfit Dislocation ◽

Strain Relaxation ◽

Three Dimensional ◽

Dislocation Network ◽

Misfit Dislocations ◽

Dislocation Loops ◽

X Ray Diffraction ◽

Si Substrate ◽

Transmission Electron ◽

Microscopy Techniques

AbstractStrain relaxation in He+-implanted and annealed Si(001)/Si1−xGex heterostructures was investigated using transmission electron microscopy techniques and x-ray diffraction. Depending on the implant conditions, bubbles and/or platelets form below the Si/Si1−xGex interface upon annealing and act as nucleation sources for dislocation loops. The dislocation loops extend to the interface and form a misfit dislocation network there, resulting in relaxation of 30-80% of the strain in layers as thin as 100-300 nm. When bubbles form close to the interface, dislocations nucleate by a climb loop mechanism. When smaller bubbles form deeper in the Si substrate an irregular three-dimensional dislocation network forms below the interface resulting in an irregular misfit dislocation network at the interface. When platelets form deeper in the Si substrate, prismatic punching of dislocation loops is observed and dislocation reactions of misfit dislocations at the interface result in Lomer dislocation formation.

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A Theoretical Calculation of Misfit Dislocation and Strain Relaxation in Step-graded InxGa 1-x N/GaN Layers

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.403-408.456 ◽

2011 ◽

Vol 403-408 ◽

pp. 456-460 ◽

Cited By ~ 1

Author(s):

Md. Arafat Hossain ◽

Md. Rafiqul Islam

Keyword(s):

Theoretical Calculation ◽

Layer Thickness ◽

Misfit Dislocation ◽

Residual Strain ◽

Critical Thickness ◽

Strain Relaxation ◽

Misfit Strain ◽

Misfit Dislocations ◽

Uniform Layer ◽

Dislocation Energy

This paper presents a theoretical calculation of misfit dislocation and strain relaxation in compositionally step graded InxGa1-xN grown on GaN using the total dislocation energy at each interface. The results also compared with uniform layer of In0.17Ga0.83N and In0.14Ga0.86N grown differently on GaN. Due to having residual strain and a step increase in indium composition a lower misfit strain in upper layers and hence larger critical thickness at each interface has been reported. These effects significantly reduced the misfit dislocations from 2.6×105cm-1to 9.5×104cm-1in step graded In0.14Ga0.86N(500nm)/In0.09Ga0.91N(100nm)/In0.05Ga0.95N(100nm)/GaN layers instead of a uniform In0.14Ga0.86N(700nm)/GaN. A small residual strain of 0.0007 after 700 nm graded layer thickness has been reported with 87.04% strain relaxation.

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Misfit Dislocation Introduction During The Epitaxial Growth of Inas Islands on Gap

MRS Proceedings ◽

10.1557/proc-673-p4.3 ◽

2001 ◽

Vol 673 ◽

Author(s):

Vidyut Gopal ◽

Alexander L. Vasiliev ◽

Eric P. Kvam

Keyword(s):

Plastic Deformation ◽

Aspect Ratio ◽

Strain Relaxation ◽

Three Dimensional ◽

Elastic Strain Energy ◽

Volume Ratio ◽

Misfit Dislocations ◽

Initial Growth ◽

Nominal Thickness ◽

Lattice Planes

ABSTRACTThe initial growth of InAs on 11% lattice mismatched GaP substrates by molecular beam epitaxy was investigated. High resolution transmission electron microscopy (HREM) images showed that the InAs grew in the form of three-dimensional islands of dissimilar sizes. Mismatch induced strain relief was effected by the direct introduction of (mostly) edge dislocations at the corners of the islands. An examination of HREM images of several islands revealed that the island aspect ratio decreased with the introduction of misfit dislocations. Strain relaxation in the smaller, relatively dislocation-free islands occurred by elastic deformation of InAs lattice planes, which was more effective far from the constrained island-substrate interface. As a result, these islands grew taller and narrower, with a gradient in the elastic strain energy. However, a higher aspect ratio resulted in a higher surface area – to – volume ratio, and increased the surface energy of the InAs islands. Consequently, there was a driving force for the reduction of the aspect ratio if an alternate avenue for strain relaxation existed. The alternate route was plastic deformation by the introduction of misfit dislocations. As the island grew, the strain at the island corners increased, and beyond a critical value, misfit dislocations were added. These dislocations relieved strain at the heterointerface, and promoted the islands to grow laterally, i.e., the aspect ratio decreased. Islands coalesced, and a continuous layer resulted by a nominal thickness of 3 nm. Thus, the morphology of InAs islands grown on GaP was determined by the balance between elastic and plastic deformation.

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Building Ferroelectric from the Bottom Up: The Machine Learning Analysis of the Atomic-Scale Ferroelectric Distortions

10.26434/chemrxiv.8001473.v1 ◽

2019 ◽

Author(s):

Maxim Ziatdinov ◽

Christopher Nelson ◽

Rama Vasudevan ◽

Deyang Chen ◽

Sergei Kalinin

Keyword(s):

Building Blocks ◽

Atomic Displacement ◽

Atomic Scale ◽

Atomic Column ◽

Bottom Up ◽

Scanning Transmission ◽

Classical Paper ◽

Full Analysis ◽

Ferroic Materials ◽

Atomic Coordinates

<div>Recent advances in scanning transmission electron microscopy (STEM) have enabled direct visualization of the atomic structure of ferroic materials, enabling the determination of atomic column positions with ~pm precision. This, in turn, enabled direct mapping of ferroelectric and ferroelastic order parameter fields via the top-down approach, where the atomic coordinates are directly mapped on the mesoscopic order parameters. Here, we explore the alternative bottom-up approach, where the atomic coordinates derived from the STEM image are used to explore the extant atomic displacement patterns in the material and build the collection of the building blocks for the distorted lattice. This approach is illustrated for the La-doped BiFeO3 system.</div><div>The full analysis procedure is available as an interactive paper in a form of a Google Colab (Jupyter) notebook where a classical paper organization is augmented with code cells that appear hidden by default (when viewed in Google Colab). This should allow a reader to retrace the analysis and, more importantly, it enables the readers to use the same codes for their data. The same paper is also available in a standard pdf format (without code). </div>

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Misfit Dislocation Free Epitaxial Growth of SiGe on Compliant Nano-Structured Silicon

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.242.402 ◽

2015 ◽

Vol 242 ◽

pp. 402-407

Author(s):

Peter Zaumseil ◽

Markus Andreas Schubert ◽

Yuji Yamamoto ◽

Oliver Skibitzki ◽

Giovanni Capellini ◽

...

Keyword(s):

Epitaxial Growth ◽

Misfit Dislocation ◽

Research Effort ◽

Strain Relaxation ◽

Misfit Dislocations ◽

Final Goal ◽

Silicon Based ◽

Nanostructured Si

The integration of germanium (Ge) into silicon-based microelectronics technologies is currently attracting increasing interest and research effort. One way to realize this without threading and misfit dislocations is the so-called nanoheteroepitaxy approach. We demonstrate that a modified Si nanostructure approach with nanopillars or bars separated by TEOS SiO2 can be used successfully to deposit SiGe dots and lines free of misfit dislocations. It was found that strain relaxation in the pseudomorphically grown SiGe happens fully elastically. These studies are important for the understanding of the behavior of nanostructured Si for the final goal of Ge integration via SiGe buffer.

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Effect of Micro-Steps on Twinning and Interfacial Segregation in Mg-Ag Alloy

Materials ◽

10.3390/ma12081307 ◽

2019 ◽

Vol 12 (8) ◽

pp. 1307 ◽

Cited By ~ 6

Author(s):

Yi Liu ◽

Xuefei Chen ◽

Kang Wei ◽

Lirong Xiao ◽

Bin Chen ◽

...

Keyword(s):

Twin Boundary ◽

Scanning Transmission Electron Microscopy ◽

Dark Field ◽

Atomic Scale ◽

Misfit Dislocations ◽

Twin Boundaries ◽

Transmission Electron ◽

Scanning Transmission ◽

Annular Dark Field ◽

Interfacial Segregation

Twinning structures and their interfacial segregation play a key role in strengthening of magnesium alloys. Micro-steps are frequently existed in the incoherent twin boundaries, while the effect of them on interface and interfacial segregation is still not clear. In this work, we performed an atomic-scale microstructure analysis using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) to explore the effect of micro-steps on twin and its interfacial segregation in Mg-Ag alloy. Diffraction pattern of the incoherent {10 1 ¯ 1} twin shows that the misorientation has a slight tilt of 5° from its theoretical angle of 125° due to the accumulated effects of the micro-steps and their misfit dislocations in twin boundaries. Most of the micro-steps in {10 1 ¯ 1} twin boundary are in the height of 2 d ( 10 1 ¯ 1 ) and 4 d ( 10 1 ¯ 1 ) , respectively, and both of them have two types according to whether there are dislocations on the micro-steps. The twin boundary is interrupted by many micro-steps, which leads to a step-line distributed interfacial segregation. Moreover, the Ag tends to segregate to dislocation cores, which results in the interruption of interfacial segregation at the micro-steps with dislocations.

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Mechanisms and Kinetics of Misfit Dislocation Formation in Heteroepitaxial Thin Films

MRS Proceedings ◽

10.1557/proc-188-315 ◽

1990 ◽

Vol 188 ◽

Cited By ~ 31

Author(s):

W. D. Nix ◽

D. B. Noble ◽

J. F. Turlo

Keyword(s):

Misfit Dislocation ◽

Strain Relaxation ◽

Dislocation Motion ◽

Dislocation Nucleation ◽

Dislocation Segment ◽

Threading Dislocation ◽

Misfit Dislocations ◽

Film Substrate ◽

Kinetics Of ◽

Dislocation Formation

ABSTRACTThe mechanisms and kinetics of forming misfit dislocations in heteroepitaxial films are studied. The critical thickness for misfit dislocation formation can be found by considering the incremental extension of a misfit dislocation by the movement of a “threading” dislocation segment that extends from the film/substrate interface to the free surface of the film. This same mechanism allows one to examine the kinetics of dislocation motion and to illuminate the importance of dislocation nucleation and multiplication in strain relaxation. The effects of unstrained epitaxial capping layers on these processes are also considered. The major effects of such capping layers are to inhibit dislocation nucleation and multiplication. The effect of the capping layer on the velocity of the “threading” dislocation is shown to be small by comparison.A new substrate curvature technique for measuring the strain and studying the kinetics of strain relaxation in heteroepitaxial films is also briefly described.

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Atomic scale structure of a plagioclase – magnetite interface

10.5194/egusphere-egu21-2432 ◽

2021 ◽

Author(s):

Ge Bian ◽

Olga Ageeva ◽

Gerlinde Habler ◽

Vladimir Roddatis ◽

Rainer Abart

Keyword(s):

Electron Microscopy ◽

Ion Beam ◽

Lattice Misfit ◽

Natural Remanent Magnetization ◽

Dark Field ◽

Atomic Scale ◽

Misfit Dislocations ◽

Orientation Relationships ◽

Plane Normal ◽

Lattice Planes

Magnetite (Mt) is the foremost carrier of rock natural remanent magnetization (NRM). Needle- and lath shaped Mt micro-inclusions in plagioclase (Pl) from gabbro often have systematic crystallographic- and shape orientation relationships (CORs, SORs) with the Pl host. The SORs of Mt leads to magnetic anisotropy which may bias the NRM of the Mt-Pl inclusion-host assemblage. Thus, the origin of the CORs and SORs between Mt and Pl is important for paleomagnetic reconstructions. In this context, the atomic structures of Mt-Pl interfaces are of particular interest.The CORs and SORs between Mt and Pl were reported earlier and the underlying systematics was revealed from correlated optical and scanning electron microscopy (SEM) including electron back scattered diffraction (EBSD) analyses [1] (and references therein). The so-called plane normal type Mt micro-inclusions extend parallel to the Mt<111> direction, which is perpendicular to the densely packed Mt{222} oxygen layers that are parallel to one of seven Pl lattice planes with nearly identical d-spacings, namely Pl(112), Pl(-312), Pl(1-50), Pl(150), Pl(100), Pl(31-2) and Pl(1-12). Direct imaging of Mt-Pl interfaces has rarely been reported due to the beam sensitivity of Pl. Here we present the microscopic structure of a Mt-Pl interface along the inclusion elongation direction using high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and integrated differential phase contrast STEM (iDPC-STEM) techniques.The TEM foil was prepared using a focused Ga-ion beam (Ga-FIB) from a lath-shaped Mt micro-inclusion of 23 &#956;m x 17 &#956;m x 0.1 &#956;m extending perpendicular to Mt{111}/Pl(-312). The foil is oriented so that the Mt<111>/Pl(-312)-pole are parallel and Mt{110}/Pl(150) planes are perpendicular to the foil.The STEM images show that the Mt-Pl interface is perfectly straight and parallel to Mt{110}/Pl(150) and that it is devoid of steps. Electron diffraction patterns confirm that the elongation direction of the micro-inclusions is determined by the good fit of oxygen layers across the Pl-Mt interface. A 2.4% difference in the d-spacings between Pl(-312) and Mt{222} is likely accommodated by every about 42'nd Mt{222} plane forming an edge dislocation at the Mt-Pl interface. In addition, elastic strain is indicated by a deviation of d111/d110 of Mt from the strain free reference lattice. Moreover, lattice fringes in iDPC-STEM images reveal coherence between Pl(22-1) and Mt{111} planes without misfit dislocations. This additional coherence may explain the particularly strong alignment of Mt{111} and Pl(-312) reflected by the EBSD data.In summary, the elongation directions of the Mt inclusions are determined by the alignment of important oxygen layers of both phases across the Mt-Pl interface, which is parallel to oxygen-rich lattice planes in both phases. Misfit dislocations are presumably introduced to compensate the 2.4% lattice misfit along the elongation direction. The well-organized interface structure ensures a low interfacial energy and is a viable explanation for the observed Mt-Pl CORs and SORs. &#160;AcknowledgementFunding by FWF project I 3998-N29 and RFBR project 18-55-14003 is acknowledged.Reference[1] Ageeva et al (2020) Contrib. Mineral. Petrol. 175(10), 1-16.

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