scholarly journals Epitaxy from a Periodic Y–O Monolayer: Growth of Single-Crystal Hexagonal YAlO3 Perovskite

Nanomaterials ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1515
Author(s):  
Minghwei Hong ◽  
Chao-Kai Cheng ◽  
Yen-Hsun Lin ◽  
Lawrence Boyu Young ◽  
Ren-Fong Cai ◽  
...  
Keyword(s):  
Single Crystal ◽  
Spherical Aberration ◽  
Annealed Film ◽  
Atomic Layer ◽  
Bottom Layer ◽  
High Energy ◽  
Dark Field ◽  
Film Deposition ◽  
Scanning Transmission ◽  
Annular Dark Field

The role of an atomic-layer thick periodic Y–O array in inducing the epitaxial growth of single-crystal hexagonal YAlO3 perovskite (H-YAP) films was studied using high-angle annular dark-field and annular bright-field scanning transmission electron microscopy in conjunction with a spherical aberration-corrected probe and in situ reflection high-energy electron diffraction. We observed the Y–O array at the interface of amorphous atomic layer deposition (ALD) sub-nano-laminated (snl) Al2O3/Y2O3 multilayers and GaAs(111)A, with the first film deposition being three cycles of ALD-Y2O3. This thin array was a seed layer for growing the H-YAP from the ALD snl multilayers with 900 °C rapid thermal annealing (RTA). The annealed film only contained H-YAP with an excellent crystallinity and an atomically sharp interface with the substrate. The initial Y–O array became the bottom layer of H-YAP, bonding with Ga, the top layer of GaAs. Using a similar ALD snl multilayer, but with the first film deposition of three ALD-Al2O3 cycles, there was no observation of a periodic atomic array at the interface. RTA of the sample to 900 °C resulted in a non-uniform film, mixing amorphous regions and island-like H-YAP domains. The results indicate that the epitaxial H-YAP was induced from the atomic-layer thick periodic Y–O array, rather than from GaAs(111)A.

Design of a new objective lens for an HB-501A STEM

1991 ◽  
Vol 49 ◽  
pp. 416-417
Author(s):  
Earl J. Kirkland ◽  
Robert J. Keyse
Keyword(s):  
High Resolution ◽  
Spherical Aberration ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
Specimen Holder ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
High Resolution Microscopy

An ultra-high resolution pole piece with a coefficient of spherical aberration Cs=0.7mm. was previously designed for a Vacuum Generators HB-501A Scanning Transmission Electron Microscope (STEM). This lens was used to produce bright field (BF) and annular dark field (ADF) images of (111) silicon with a lattice spacing of 1.92 Å. In this microscope the specimen must be loaded into the lens through the top bore (or exit bore, electrons traveling from the bottom to the top). Thus the top bore must be rather large to accommodate the specimen holder. Unfortunately, a large bore is not ideal for producing low aberrations. The old lens was thus highly asymmetrical, with an upper bore of 8.0mm. Even with this large upper bore it has not been possible to produce a tilting stage, which hampers high resolution microscopy.

Microstructure and interdiffusion behaviour of β-FeSi2 flat islands grown on Si(111) surfaces

2013 ◽  
Vol 46 (4) ◽  
pp. 1076-1080
Author(s):  
Sung-Pyo Cho ◽  
Yoshiaki Nakamura ◽  
Jun Yamasaki ◽  
Eiji Okunishi ◽  
Masakazu Ichikawa ◽  
...  
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Single Phase ◽  
Spherical Aberration ◽  
Dark Field ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Abrupt Interface ◽  
Average Size ◽  
20 Nm

β-FeSi2 flat islands have been fabricated on ultra-thin oxidized Si(111) surfaces by Fe deposition on Si nanodots. The microstructure and interdiffusion behaviour of the β-FeSi2/Si(111) system at the atomic level were studied by using spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. The formed β-FeSi2 flat islands had a disc shape with an average size of 30–150 nm width and 10–20 nm height, and were epitaxically grown on high-quality single-phase Si with a crystallographic relationship (110)β-FeSi2/(111)Si and [001]β-FeSi2/[1\bar 10]Si. Moreover, the heterojunction between the β-FeSi2(110) flat islands and the Si(111) substrate was an atomically and chemically abrupt interface without any irregularities. It is believed that these results are caused by the use of ultra-thin SiO2 films in our fabrication method, which is likely to be beneficial particularly for fabricating practical nanoscaled devices.

The quasiperiodic average structure of highly disordered decagonal Zn–Mg–Dy and its temperature dependence

2014 ◽  
Vol 70 (2) ◽  
pp. 315-330 ◽  
Author(s):  
Taylan Ors ◽  
Hiroyuki Takakura ◽  
Eiji Abe ◽  
Walter Steurer
Keyword(s):  
Single Crystal ◽  
Decomposition Temperature ◽  
Dark Field ◽  
Penrose Tiling ◽  
X Ray Diffraction ◽  
Decagonal Quasicrystal ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field

A single-crystal X-ray diffraction structure analysis of decagonal Zn–Mg–Dy, a Frank–Kasper-type quasicrystal, was performed using the higher-dimensional approach. For this first Frank–Kasper (F–K) decagonal quasicrystal studied so far, significant differences to the decagonal Al–TM-based (TM: transition metal) phases were found. A new type of twofold occupation domain is located on certain edge centers of the five-dimensional unit cell. The structure can be described in terms of a two-cluster model based on a decagonal cluster (∼ 23 Å diameter) arranged on the vertices of a pentagon-Penrose tiling (PPT) and a star-like cluster covering the remaining space. This model is used for the five-dimensional refinements, which converged to anRvalue of 0.126. The arrangement of clusters is significantly disordered as indicated by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). In order to check the structure and stability at higher temperatures,in-situhigh-temperature (HT) single-crystal X-ray diffraction experiments were conducted at 598 and 648 K (i.e.slightly below the decomposition temperature). The structure does not change significantly, however, the best quasiperiodic order is found at 598 K. The implication of these results on the stabilization mechanism of quasicrystals is discussed.

Mn Valency at La0.7Sr0.3MnO3/SrTiO3 (0 0 1) Thin Film Interfaces

2009 ◽  
Vol 15 (3) ◽  
pp. 213-221 ◽  
Author(s):  
Thomas Riedl ◽  
Thomas Gemming ◽  
Kathrin Dörr ◽  
Martina Luysberg ◽  
Klaus Wetzig
Keyword(s):  
Thin Film ◽  
High Resolution ◽  
Scanning Transmission Electron Microscopy ◽  
Atomic Layer ◽  
Dark Field ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
High Resolution Images ◽  
Local Oxygen

AbstractThis article presents a (scanning) transmission electron microscopy (TEM) study of Mn valency and its structural origin at La0.7Sr0.3MnO3/SrTiO3(0 0 1) thin film interfaces. Mn valency deviations can lead to a breakdown of ferromagnetic order and thus lower the tunneling magnetoresistance of tunnel junctions. Here, at the interface, a Mn valency reduction of 0.16 ± 0.10 compared to the film interior and an additional feature at the low energy-loss flank of the Mn-L3 line have been observed. The latter may be attributed to an elongation of the (0 0 1) plane spacing at the interface detected by geometrical phase analysis of high-resolution images. Regarding the interface geometry, high-resolution high-angle annular dark-field scanning TEM images reveal an atomically sharp interface in some regions whereas the transition appears broadened in others. This can be explained by the presence of steps. The performed measurements indicate that, among the various structure-related influences on the valency, the atomic layer termination and the local oxygen content are most important.

Preparation of Ultrafine Supported Clusters for Electron Microscopy Studies

1995 ◽  
Vol 404 ◽  
Author(s):  
A. Singhal ◽  
J. Murray Gibson
Keyword(s):  
Electron Microscopy ◽  
High Energy ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Scattered Electron ◽  
Fragmentation Behavior ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Electron Intensity

AbstractIn this paper, we discuss the sintering/fragmentation behavior of novel oganometallic rhenium compounds (candidates as catalyst materials) under high energy electron beam irradiation. The technique used was quantitative electron microscopy based on high angle annular dark field (HAADF) imaging in a scanning transmission electron microscope (STEM). Using this approach, we examine elastically-scattered electron intensity from graphite-supported rhenium clusters, and look for mass quantization. The emphasis in this article is not on the imaging technique, but on various sample preparation techniques, materials and synthesis issues of supports and of deposition of very small isolated clusters.

Materials analysis by aberration-corrected STEM

2004 ◽  
Vol 839 ◽  
Author(s):  
Ondrej L. Krivanek ◽  
Neil J. Bacon ◽  
George C. Corbin ◽  
Niklas Dellby ◽  
Andrew McManama-Smith ◽  
...  
Keyword(s):  
Spherical Aberration ◽  
Dark Field ◽  
Optical Aberration ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Powerful Research Tool ◽  
Electron Microscopes ◽  
Electron Energy Loss ◽  
Aberration Corrected

ABSTRACTElectron-optical aberration correction has recently progressed from a promising concept to a powerful research tool. 100–120 kV scanning transmission electron microscopes (STEMs) equipped with spherical aberration (Cs) correctors now achieve sub-Å resolution in high-angle annular dark field (HAADF) imaging, and a 300 kV Cs-corrected STEM has reached 0.6 Å HAADF resolution. Moreover, the current available in an atom-sized probe has grown by about 10x, allowing electron energy loss spectroscopy (EELS) to detect single atoms. We summarize the factors that have made this possible, and outline likely future progress.

scholarly journals Phase transformation from PbS to PbSe:S in hot-wall deposition of nanocomposite thin film with evaporation sources of PbS and ZnSe

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Seishi Abe
Keyword(s):  
Peak Position ◽  
Dark Field ◽  
Film Deposition ◽  
X Ray Diffraction ◽  
Wavelength Dispersive Spectroscopy ◽  
Wall Deposition ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Diffraction Patterns

AbstractSimultaneous evaporation of PbS and ZnSe using hot-wall deposition was investigated to prepare nanocomposite thin films. X-ray diffraction patterns indicated that the films formed a phase mixture of ZnSe and PbSe, suggesting that an evaporation source of PbS phase-transformed to PbSe during a film deposition. Wavelength-dispersive spectroscopy indicated that the composite contains a small amount of S below 1 at.%. High-angle annular dark-field scanning transmission electron microscopy and line scan analysis in electron energy-loss spectroscopy indicated that PbSe nanocrystals were dispersed in a ZnSe, while S tended to segregate in ZnSe matrix. Photocurrent spectra indicated that peak position at approximately 460 nm shifted toward a shorter wavelength as Pb concentration increased.

Resolution in the Scanning Transmission Electron Microscope

1972 ◽  
Vol 30 ◽  
pp. 454-455
Author(s):  
M. G. R. Thomson
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Spherical Aberration ◽  
Signal To Noise Ratio ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The variation of contrast and signal to noise ratio with change in detector solid angle in the high resolution scanning transmission electron microscope was discussed in an earlier paper. In that paper the conclusions were that the most favourable conditions for the imaging of isolated single heavy atoms were, using the notation in figure 1, either bright field phase contrast with β0⋍0.5 α0, or dark field with an annular detector subtending an angle between ao and effectively π/2.The microscope is represented simply by the model illustrated in figure 1, and the objective lens is characterised by its coefficient of spherical aberration Cs. All the results for the Scanning Transmission Electron Microscope (STEM) may with care be applied to the Conventional Electron Microscope (CEM). The object atom is represented as detailed in reference 2, except that ϕ(θ) is taken to be the constant ϕ(0) to simplify the integration. This is reasonable for θ ≤ 0.1 θ0, where 60 is the screening angle.

Simulation of high-resolution annular dark field STEM images

1995 ◽  
Vol 53 ◽  
pp. 40-41
Author(s):  
E. J. Kirkland
Keyword(s):  
Electron Beam ◽  
Atomic Layer ◽  
Fresnel Diffraction ◽  
Dark Field ◽  
Objective Lens ◽  
Image Simulation ◽  
Small Probe ◽  
Annular Dark Field ◽  
Stem Image ◽  
Uniform Plane

In a STEM an electron beam is focused into a small probe on the specimen. This probe is raster scanned across the specimen to form an image from the electrons transmitted through the specimen. The objective lens is positioned before the specimen instead of after the specimen as in a CTEM. Because the probe is focused and scanned before the specimen, accurate annular dark field (ADF) STEM image simulation is more difficult than CTEM simulation. Instead of an incident uniform plane wave, ADF-STEM simulation starts with a probe wavefunction focused at a specified position on the specimen. The wavefunction is then propagated through the specimen one atomic layer (or slice) at a time with Fresnel diffraction between slices using the multislice method. After passing through the specimen the wavefunction is diffracted onto the detector. The ADF signal for one position of the probe is formed by integrating all electrons scattered outside of an inner angle large compared with the objective aperture.

Atomic resolution Z-contrast imaging of bulk crystal surfaces in Scanning Reflection Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 414-415
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
Electron Microscopy ◽  
Elastic Scattering ◽  
Dark Field ◽  
Contrast Imaging ◽  
Crystal Lattices ◽  
Small Probe ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Image Position ◽  
Z Contrast

The success of obtaining atomic-number-sensitive (Z-contrast) images in scanning transmission electron microscopy (STEM) has shown the feasibility of imaging composition changes at the atomic level. This type of image is formed by collecting the electrons scattered through large angles when a small probe scans across the specimen. The image contrast is determined by two scattering processes. One is the high angle elastic scattering from the nuclear sites,where ϕNe is the electron probe function centered at bp = (Xp, yp) after penetrating through the crystal; F denotes a Fourier transform operation; D is the detection function of the annular-dark-field (ADF) detector in reciprocal space u. The other process is thermal diffuse scattering (TDS), which is more important than the elastic contribution for specimens thicker than about 10 nm, and thus dominates the Z-contrast image. The TDS is an average “elastic” scattering of the electrons from crystal lattices of different thermal vibrational configurations,

Sign in / Sign up

Export Citation Format

Share Document