Domain matching epitaxy stabilized metastable, tetragonal BiFeO3 on symmetry-mismatched c-plane ZnO

2021 ◽  
Author(s):  
Yajuan Zhao ◽  
Zhigang Yin ◽  
Xingxing Li ◽  
Maoyuan Zheng ◽  
Yong Cheng ◽  
...  
Keyword(s):  
Critical Thickness ◽  
Lattice Mismatch ◽  
Rhombohedral Phase ◽  
Tetragonal Symmetry ◽  
Formula Unit ◽  
Monoclinic Structure ◽  
X Ray ◽  
Oxide Electronics ◽  
Domain Matching Epitaxy ◽  
Bifeo3 Film

Abstract We report the stabilization of metastable tetragonal BiFeO3 epilayer on ZnO(0001) surface. X-ray reciprocal space map characterizations show that the BiFeO3 film is of true tetragonal symmetry, but not the commonly observed monoclinic structure. The critical thickness of the tetragonal BiFeO3 is higher than 140 nm, much larger than that reported previously. Despite the considerable lattice mismatch and symmetry mismatch, tetragonal BiFeO3 can be formed on ZnO(0001) though domain matching epitaxy which is featured by anisotropic growth. We show that by taking into account the elastic energy during the initial semi-coherent growth, the tetragonal phase is lower than the thermally stable rhombohedral phase in total energy by 70 meV per formula unit. Moreover, local piezoelectric characterizations reveal a coercive field of 360 kV/cm and a piezoelectric constant of 48 pm/V. The integration of tetragonal BiFeO3 with robust ferroelectricity on the platform of ZnO has potentials for all-oxide electronics applications.

Misfit dislocations between boron-doped homoepitaxial films and diamond substrates studied by X-ray diffraction topography

2018 ◽  
Vol 51 (6) ◽  
pp. 1684-1690 ◽  
Author(s):  
Marina González-Mañas ◽  
Beatriz Vallejo
Keyword(s):  
Critical Thickness ◽  
Lattice Mismatch ◽  
Lattice Parameter ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Boron Doped Diamond ◽  
X Ray ◽  
Boron Doped ◽  
Slip Planes ◽  
Half Loop

Boron-doped diamond epilayers grown over diamond substrates have a different lattice parameter from the undoped diamond substrate, which introduces a lattice mismatch between substrates and epilayers. This can generate misfit dislocations at the interface when the epilayer reaches a certain critical thickness. For a boron concentration of about 1 × 1020 atoms cm−3, the calculated lattice mismatch is about 1.3 × 10−4 and the critical thickness is of the order of 0.2 µm. In the epilayers studied, grown over high-pressure high-temperature 1b (001) substrates, the lattice mismatch and the epilayer thickness are 1.3 × 10−4, 30 µm and 6.5 × 10−4, 4 µm. The epitaxial strain has been relaxed by the generation of two orthogonal misfit dislocation systems. These are edge dislocations parallel to the [100] and [010] directions with a Burgers vector making an angle of 45° with the (001) interface. Their lengths are 40–60 µm and their lineal densities 200–240 cm−1. They are heterogeneously nucleated, propagated in the form of half-loops along the slip planes (011) and (101), respectively, and related mainly to 〈111〉 threading dislocations emerging from octahedral growth sectors. Another kind of half-loop originates from the substrate growth sector boundaries. Limited X-ray topography has been demonstrated to be a very useful tool to discriminate between substrate and epilayer defects when their lattice mismatch is not sufficient to separate such defects in conventional Lang topography. X-ray section topography has confirmed the presence of [001] dislocations in the epilayers and the misfit half-loops related to threading dislocations propagating from the interface.

Structural and Hydriding/Dehydriding Properties of HoMn2Hx with Cubic and Hexagonal Laves Phase Structure

2006 ◽  
Vol 927 ◽  
Author(s):  
Yoshikazu Makihara ◽  
Youichi Iwata ◽  
Kazumi Umeda ◽  
Yoshio Miyairi ◽  
Hironobu Fujii
Keyword(s):  
Thermal Analysis ◽  
Room Temperature ◽  
Rhombohedral Phase ◽  
Hydrogen Desorption ◽  
Hexagonal Structure ◽  
Laves Phase ◽  
Formula Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Laves Phase Compounds

ABSTRACTBoth the cubic C15-type and the hexagonal C14-type Laves phase compounds HoMn2 were successfully prepared. We found that they absorbed hydrogen up to 3.4 atoms per formula unit at room temperature and discharged it at around 490 K, reversibly. Structural and hydriding/dehydriding properties of the host HoMn2 and their hydrides HoMn2Hx have been investigated by powder X-ray diffraction (XRD) and thermogravimetry/differential thermal analysis (TG/DTA). With increasing the hydrogen content, the host C15-type HoMn2 is distorted into a rhombohedral phase at above x = 2.9, while the host C14-type one keeps the hexagonal structure up to x = 3.4. The experimental results obtained from TG/DTA measurement suggest that two possible interstitial sites with different activation energies for hydrogen desorption exist in the C14 HoMn2, while one site in the C15 HoMn2.

Chemical partitioning of elements in Ni-base MC-carbide reinforced eutetic superalloys

1983 ◽  
Vol 41 ◽  
pp. 250-251
Author(s):  
E. F. Koch ◽  
E. L. Hall ◽  
S. W. Yang
Keyword(s):  
Alloy Composition ◽  
Volume Fraction ◽  
Lattice Mismatch ◽  
Turbine Blades ◽  
Eutectic Alloys ◽  
Alloy Matrix ◽  
X Ray ◽  
Gas Turbine Blades ◽  
Analytical Electron ◽  
Analytical Electron Microscope

The plane-front solidified eutectic alloys consisting of aligned tantalum monocarbide fibers in a nickel alloy matrix are currently under consideration for future aircraft and gas turbine blades. The MC fibers provide exceptional strength at high temperatures. In these alloys, the Ni matrix is strengthened by the precipitation of the coherent γ' phase (ordered L12 structure, nominally Ni3Al). The mechanical strength of these materials can be sensitively affected by overall alloy composition, and these strength variations can be due to several factors, including changes in solid solution strength of the γ matrix, changes in they γ' size or morphology, changes in the γ-γ' lattice mismatch or interfacial energy, or changes in the MC morphology, volume fraction, thermal stability, and stoichiometry. In order to differentiate between these various mechanisms, it is necessary to determine the partitioning of elemental additions between the γ,γ', and MC phases. This paper describes the results of such a study using energy dispersive X-ray spectroscopy in the analytical electron microscope.

Structural properties of GaAs/InGaAs/GaAs (001) and InGaAs/GaAs (001) heterostructures and correlation with electronic properties

1990 ◽  
Vol 48 (4) ◽  
pp. 602-603
Author(s):  
J.M. Bonar ◽  
R. Hull ◽  
R. Malik ◽  
R. Ryan ◽  
J.F. Walker
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Gaas Substrate ◽  
Critical Thickness ◽  
Lattice Mismatch ◽  
Band Offset ◽  
Misfit Dislocations ◽  
Gaas Substrates ◽  
Gaas Structure ◽  
Low X

In this study we have examined a series of strained heteropeitaxial GaAs/InGaAs/GaAs and InGaAs/GaAs structures, both on (001) GaAs substrates. These heterostructures are potentially very interesting from a device standpoint because of improved band gap properties (InAs has a much smaller band gap than GaAs so there is a large band offset at the InGaAs/GaAs interface), and because of the much higher mobility of InAs. However, there is a 7.2% lattice mismatch between InAs and GaAs, so an InxGa1-xAs layer in a GaAs structure with even relatively low x will have a large amount of strain, and misfit dislocations are expected to form above some critical thickness. We attempt here to correlate the effect of misfit dislocations on the electronic properties of this material.The samples we examined consisted of 200Å InxGa1-xAs layered in a hetero-junction bipolar transistor (HBT) structure (InxGa1-xAs on top of a (001) GaAs buffer, followed by more GaAs, then a layer of AlGaAs and a GaAs cap), and a series consisting of a 200Å layer of InxGa1-xAs on a (001) GaAs substrate.

scholarly journals Photoconductivity of the Single Crystals Pb4Ga4GeS12 and Pb4Ga4GeSe12

Proceedings ◽  
2020 ◽  
Vol 62 (1) ◽  
pp. 4
Author(s):  
Hadj Bellagra ◽  
Oksana Nyhmatullina ◽  
Yuri Kogut ◽  
Halyna Myronchuk ◽  
Lyudmyla Piskach
Keyword(s):  
Ternary Systems ◽  
Semiconductor Materials ◽  
Tetragonal Symmetry ◽  
Bandgap Energy ◽  
Experimental Measurements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vertical Bridgman ◽  
Symmetry Space ◽  
Symmetry Space Group

Quaternary semiconductor materials of the Pb4Ga4GeS(Se)12 composition have attracted the attention of researchers due to their possible use as active elements of optoelectronics and nonlinear optics. The Pb4Ga4GeS(Se)12 phases belong to the solid solution ranges of the Pb3Ga2GeS(Se)8 compounds which form in the quasi-ternary systems PbS(Se)−Ga2S(Se)3−GeS(Se)2 at the cross of the PbGa2S(Se)4−Pb2GeS(Se)4 and PbS(Se)−PbGa2GeS(Se)6 sections. The quaternary sulfide melts congruently at 943 K. The crystallization of the Pb4Ga4GeSe12 phase is associated with the ternary peritectic process Lp + PbSe ↔ PbGa2S4 + Pb3Ga2GeSe8 at 868 K. For the single crystal studies, Pb4Ga4GeS(Se)12 were pre-synthesized by co-melting high-purity elements. The X-ray diffraction results confirm that these compounds possess non-centrosymmetric crystal structure (tetragonal symmetry, space group P–421c). The crystals were grown by the vertical Bridgman method in a two-zone furnace. The starting composition was stoichiometric for Pb4Ga4GeS12, and the solution-melt method was used for the selenide Pb4Ga4GeSe12. The obtained value of the bandgap energy for the Pb4Ga4GeS12 and Pb4Ga4GeSe12 crystals is 1.86 and 2.28 eV, respectively. Experimental measurements of the spectral distribution of photoconductivity for the Pb4Ga4GeS12 and Pb4Ga4GeSe12 crystals exhibit the presence of two spectral maxima. The first lies in the region of 570 (2.17 eV) and 680 nm (1.82 eV), respectively, and matches the optical bandgap estimates well. The locations of the admixture maxima at about 1030 (1.20 eV) and 1340 nm (0.92 eV), respectively, agree satisfactorily with the calculated energy positions of the defects vs. and VSe.

Time Dependence of γ/γ' Lattice Mismatch in Creep-Deformed Single Crystal Superalloy SC16 at 1173 K

2007 ◽  
Vol 539-543 ◽  
pp. 3059-3063 ◽  
Author(s):  
G. Schumacher ◽  
N. Darowski ◽  
I. Zizak ◽  
Hellmuth Klingelhöffer ◽  
W. Chen ◽  
...  
Keyword(s):  
Single Crystal ◽  
Lattice Mismatch ◽  
Lattice Misfit ◽  
Peak Position ◽  
Single Crystal Superalloy ◽  
Tensile Creep ◽  
Full Width ◽  
X Ray Diffraction ◽  
X Ray ◽  
Time Period

The profiles of 001 and 002 reflections have been measured at 1173 K as a function of time by means of X-ray diffraction (XRD) on tensile-creep deformed specimens of single crystal superalloy SC16. Decrease in line width (full width at half maximum: FWHM) by about 7 % and increase in peak position by about 3x10-4 degrees was detected after 8.5x104 s. Broadening of the 002 peak profile indicated a more negative value of the lattice misfit after the same time period. The results are discussed in the context of the anisotropic arrangement of dislocations at the γ/γ’ interfaces during creep and their rearrangement during the thermal treatment at 1173 K.

Strain Analysis in Thin La1−xCaxMnO3 Films by Grazing Incidence X-ray Scattering

1999 ◽  
Vol 602 ◽  
Author(s):  
M. Petit ◽  
L. J. Martinez-Miranda ◽  
M. Rajeswari ◽  
A. Biswas ◽  
D. J. Kang ◽  
...  
Keyword(s):  
Film Thickness ◽  
Lattice Mismatch ◽  
Compressive Strain ◽  
Strain Analysis ◽  
Grazing Incidence ◽  
Relaxation Processes ◽  
Near Surface ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

AbstractWe have performed depth profile analyses of the lattice parameters in epitaxial thin films of La1−xCaxMno3 (LCMO), where x = 0.33 or 0.3, to understand the evolution of strain relaxation processes in these materials. The analyses were done using Grazing Incidence X-ray Scattering (GIXS) on films of different thicnesses on two different substrates, (100) oriented LaAlO3 (LAO), with a lattice mismatch of ∼2% and (110) oriented NGO, with a lattice mismatch of less than 0.1%. Films grown on LAO can exhibit up to three in-plane strained lattice constants, corresponding to a slight orthorhombic distortion of the crystal, as well as near-surface and columnar lattice relaxation. As a function of film thickness, a crossover from a strained film to a mixture of strained and relaxed regions in the film occurs in the range of 700 Å. The structural evolution at this thickness coincides with a change in the resistivity curve near the metalinsulator transition. The in-plane compressive strain has a range of 0.2 – 1.5%, depending on the film thickness for filsm in the range of 400 - 1500 A.

Optical and structural prorerties of InAs epilayer on graded InGaAs

2001 ◽  
Vol 696 ◽  
Author(s):  
Gu Hyun Kim ◽  
Jung Bum Choi ◽  
Joo In Lee ◽  
Se-Kyung Kang ◽  
Seung Il Ban ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Residual Strain ◽  
Molecular Beam ◽  
Lattice Mismatch ◽  
Peak Position ◽  
Excitation Intensity ◽  
Total Thickness ◽  
Ingaas Layer ◽  
X Ray Diffraction ◽  
X Ray

AbstractWe have studied infrared photoluminescence (PL) and x-ray diffraction (XRD) of 400 nm and 1500 nm thick InAs epilayers on GaAs, and 4 nm thick InAs on graded InGaAs layer with total thickness of 300 nm grown by molecular beam epitaxy. The PL peak positions of 400 nm, 1500 nm and 4 nm InAs epilayer measured at 10 K are blue-shifted from that of InAs bulk by 6.5, 4.5, and 6 meV, respectively, which can be largely explained by the residual strain in the epilayer. The residual strain caused by the lattice mismatch between InAs and GaAs or graded InGaAs/GaAs was observed from XRD measurements. While the PL peak position of 400 nm thick InAs layer is linearly shifted toward higher energy with increase in excitation intensity ranging from 10 to 140 mW, those of 4 nm InAs epilayer on InGaAs and 1500 nm InAs layer on GaAs is gradually blue-shifted and then, saturated above a power of 75 mW. These results suggest that adopting a graded InGaAs layer between InAs and GaAs can efficiently reduce the strain due to lattice mismatch in the structure of InAs/GaAs.

An X-ray scattering study on inverted Ge–Si huts grown at low temperatures

2004 ◽  
Vol 19 (4) ◽  
pp. 347-351
Author(s):  
J. Xu ◽  
X. S. Wu ◽  
B. Qian ◽  
J. F. Feng ◽  
S. S. Jiang ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Lattice Strain ◽  
Lattice Mismatch ◽  
Grazing Incidence ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Large Lattice ◽  
Scattering Study

Ge–Si inverted huts, which formed at the Si∕Ge interface of Si∕Ge superlattice grown at low temperatures, have been measured by X-ray diffraction, grazing incidence X-ray specular and off-specular reflectivities, and transmission electron microscopy (TEM). The surface of the Si∕Ge superlattice is smooth, and there are no Ge–Si huts appearing on the surface. The roughness of the surfaces is less than 3 Å. Large lattice strain induced by lattice mismatch between Si and Ge is found to be relaxed because of the intermixing of Ge and Si at the Si∕Ge interface.

scholarly journals Additive-Free Rice Starch-Assisted Synthesis of Spherical Nanostructured Hematite for Degradation of Dye Contaminant

Nanomaterials ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 702 ◽  
Author(s):  
Juan Matmin ◽  
Irwan Affendi ◽  
Salizatul Ibrahim ◽  
Salasiah Endud
Keyword(s):  
Electron Microscopy ◽  
Diffuse Reflectance Spectroscopy ◽  
Volume Ratio ◽  
Rhombohedral Phase ◽  
Nitrogen Adsorption ◽  
Rice Starch ◽  
Blue Dye ◽  
Synthesis Methods ◽  
X Ray ◽  
Stabilizing Agents

Nanostructured hematite materials for advanced applications are conventionally prepared with the presence of additives, tainting its purity with remnants of copolymer surfactants, active chelating molecules, stabilizing agents, or co-precipitating salts. Thus, preparing nanostructured hematite via additive-free and green synthesis methods remains a huge hurdle. This study presents an environmentally friendly and facile synthesis of spherical nanostructured hematite (Sp-HNP) using rice starch-assisted synthesis. The physicochemical properties of the Sp-HNP were investigated by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DR UV-Vis), and nitrogen adsorption–desorption analysis. The Sp-HNP showed a well-crystallized structure of pure rhombohedral phase, having a spherical-shaped morphology from 24 to 48 nm, and a surface area of 20.04 m2/g. Moreover, the Sp-HNP exhibited enhanced photocatalytic degradation of methylene blue dye, owing to the large surface-to-volume ratio. The current work has provided a sustainable synthesis route to produce spherical nanostructured hematite without the use of any hazardous agents or toxic additives, in agreement with the principles of green chemistry for the degradation of dye contaminant.

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