The Characterisation of The Compositional and Electronic Profiles of Delta-Doped Layers Using Transmission Electron Microscopy

1994 ◽  
Vol 354 ◽  
Author(s):  
R.E. Dunin-Borkowski ◽  
W.M. Stobbs
Keyword(s):  
Neutral Atom ◽  
Thin Layers ◽  
Free Carriers ◽  
Atom Scattering ◽  
Transmission Electron ◽  
Low Concentrations ◽  
Impurity Ions ◽  
Scattering Factor ◽  
Scattering Potential ◽  
Charged Ions

AbstractThe compositional profile of an interlayer inferred from Fresnel contrast data is usually determined assuming that the variation in the measured mean forward scattering potential is associated with changes in neutral atom scattering factor and atomic density. However, the technique is currently being applied to systems for which the form and the magnitude of the potential at the layer can be affected strongly by changes in ionicity. Here, we show how the analysis of ‘delta-doped’ layers in semiconductors, which contain thin layers of impurity ions at low concentrations, requires the analysis of not only the effect of strains on the density but also the contribution to the potential from charged ions surrounded by a wider spread of free carriers.

Magnetization, micro-x-ray fluorescence, and transmission electron microscopy studies of low concentrations of nanoscale Fe3O4 particles in epoxy resin

2000 ◽  
Vol 15 (11) ◽  
pp. 2488-2493 ◽  
Author(s):  
A. N. Thorpe ◽  
F. E. Senftle ◽  
M. Holt ◽  
J. Grant ◽  
W. Lowe ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Epoxy Resin ◽  
Magnetization Measurements ◽  
X Ray ◽  
Transmission Electron ◽  
Low Concentrations ◽  
Magnetite Particles ◽  
Spherical Agglomerates ◽  
Photon Source

Magnetization measurements, transmission electron microscopy (TEM), and high-resolution micro-x-ray fluorescence (μ-XRF) using a synchrotron radiation source (Advanced Photon Source) were used to examine Fe3O4 particle agglomerates of nominally 10-nm particles at low concentrations (down to 0.03%) in thick epoxy resin samples. The magnetization measurements showed that at low concentrations (<0.5%) the magnetite particles, although closely packed in the agglomerates, did not interact magnetically. Predicated on a 2-μm sample step scan, the μ-XRF results were compatible with the presence of spherical agglomerates due to magnetostatic attraction, and these ranged in size from 100 to several thousand nanometers, as observed in TEM measurements. At smaller step scans the resolution could be significantly improved. Thus, the synchroton μ-XRF method was very useful in detecting very small concentrations of particles in thick samples and could probably be used to detect particles in amounts as low as 10−16 g.

scholarly journals The abTEM code: transmission electron microscopy from first principles

2021 ◽  
Vol 1 ◽  
pp. 24
Author(s):  
Jacob Madsen ◽  
Toma Susi
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Open Source ◽  
Density Functional ◽  
Hexagonal Boron Nitride ◽  
Phase Reconstruction ◽  
Simulation Code ◽  
Atomic Simulation ◽  
Transmission Electron ◽  
Scattering Potential

Simulation of transmission electron microscopy (TEM) images or diffraction patterns is often required to interpret experimental data. Since nuclear cores dominate electron scattering, the scattering potential is typically described using the independent atom model, which completely neglects valence bonding and its effect on the transmitting electrons. As instrumentation has advanced, new measurements have revealed subtle details of the scattering potential that were previously not accessible to experiment. We have created an open-source simulation code designed to meet these demands by integrating the ability to calculate the potential via density functional theory (DFT) with a flexible modular software design. abTEM can simulate most standard imaging modes and incorporates the latest algorithmic developments. The development of new techniques requires a program that is accessible to domain experts without extensive programming experience. abTEM is written purely in Python and designed for easy modification and extension. The effective use of modern open-source libraries makes the performance of abTEM highly competitive with existing optimized codes on both CPUs and GPUs and allows us to leverage an extensive ecosystem of libraries, such as the Atomic Simulation Environment and the DFT code GPAW. abTEM is designed to work in an interactive Python notebook, creating a seamless and reproducible workflow from defining an atomic structure, calculating molecular dynamics (MD) and electrostatic potentials, to the analysis of results, all in a single, easy-to-read document.  This article provides ongoing documentation of abTEM development. In this first version, we show use cases for hexagonal boron nitride, where valence bonding can be detected, a 4D-STEM simulation of molybdenum disulfide including ptychographic phase reconstruction, a comparison of MD and frozen phonon modeling for convergent-beam electron diffraction of a 2.6-million-atom silicon system, and a performance comparison of our fast implementation of the PRISM algorithm for a decahedral 20000-atom gold nanoparticle.

EVIDENCE OF MULTIPARTICLE OPTICAL CENTERS IN LiNbO3:Er3+-Yb3+ CRYSTAL

2012 ◽  
Vol 15 ◽  
pp. 85-90 ◽  
Author(s):  
V.G. BABAJANYAN ◽  
R.B. KOSTANYAN ◽  
P.H. MUZHIKYAN
Keyword(s):  
Lithium Niobate ◽  
Characteristic Feature ◽  
Form Complex ◽  
Pulsed Excitation ◽  
Fluorescent Signal ◽  
Low Concentrations ◽  
Impurity Ions ◽  
Lithium Niobate Crystals ◽  
Continuous Excitation

A characteristic feature of doped lithium niobate crystals is the liability of its structure to form complex multiparticle optical centers, which consist of two or more closely spaced trivalent impurity ions, even at low concentrations of dopants. This paper presents the results of studies aimed at identifying the characteristics of such centers in the fluorescent signal of the crystal LiNbO 3: Er 3+- Yb 3+ by combination of pulsed excitation at a wavelength of 808 nm with continuous excitation at 980 nm.

Characterization of interlayer forces in 2D heterostructures using neutral atom scattering

2D Materials ◽  
2018 ◽  
Vol 5 (4) ◽  
pp. 045002 ◽  
Author(s):  
Amjad Al Taleb ◽  
Gloria Anemone ◽  
Rodolfo Miranda ◽  
Daniel Farías
Keyword(s):  
Neutral Atom ◽  
Atom Scattering

Pulsed Ion-Beam Induced Reactions of Ni And Co With Amorphous and Single Crystal Silicon

1984 ◽  
Vol 35 ◽  
Author(s):  
J. O. Olowolafe ◽  
R. Fastow
Keyword(s):  
Amorphous Silicon ◽  
Ion Beam ◽  
Single Crystal Silicon ◽  
Reaction Rates ◽  
Rutherford Backscattering ◽  
Thin Layers ◽  
X Ray Diffraction ◽  
Furnace Annealing ◽  
Crystal Silicon ◽  
Transmission Electron

ABSTRACTThin layers (~1,000 A ) of Ni and Co have been reacted with both (100) and amorphous silicon (a-Si) using a pulsed ion beam. Samples were analyzed using Rutherford backscattering, x-ray diffraction, and transmission electron microscopy. Rutherford backscattering showed that the metal/a-Si and metal/(100)-Si reaction rates were comparable. Both reactions began at the composition of the lowest eutectic. For comparison. furnace annealing of the same structures showed that the reaction rate of Ni with amorphous silicon was greater than with (100) Si; Co reacted nearly identically with both substrates. Diffraction data suggest that pulsed ion beam annealing crystallizes the amorphous silicon before the metal/a-Si reaction begins.

Study of Photovoltaic Devices with Hybrid Active Layer

2019 ◽  
Vol 293 ◽  
pp. 51-64
Author(s):  
Pawel Jarka ◽  
Tomasz Tański ◽  
Bartlomiej Hrapkowicz ◽  
Barbara Hajduk ◽  
Kamil Bystroń ◽  
...  
Keyword(s):  
Optical Properties ◽  
Bulk Heterojunction ◽  
Photovoltaic Cells ◽  
Deposition Process ◽  
Thin Layers ◽  
Force Microscopy ◽  
Active Layers ◽  
Transmission Electron ◽  
Current Voltage ◽  
The Individual

The aim of this work is to present the influences of composition of the material and manufacturing technology conditions of the organic photovoltaics devices (OPv) with the organic and hybrid bulk heterojunction on the active layers properties and cells performance. The layers were produced by using small molecular compounds: the metal-phthalocyanine (MePc) and perylene derivatives (PTCDA) and the titanium dioxide (TiO2) nanoparticles. Two kinds of metal phthalocyanines (NiPc, TiOPc) were used as donor material and pperylenetetracarboxylic dianhydride (PTCDA) as an acceptor. The used manufacturing technique allowed to employ thin layers of materials in a fast deposition process. Bulk heterojunction was created by simultaneously applying the MePc:PTCDA materials during the evaporation of the components mixture.The research was based on the estimate of composition of bulk heterojunction, the examination of the surface morphology of the used layers and optical properties studies of the heterojunction and its implementation to photovoltaic architecture. The produced photovoltaic cells parameters were determined on the basis of current - voltage characteristics.The researches of structure of obtained layers were conducted by using scanning electron microscope (SEM) and transmission electron microscopy (TEM). The quantitative determination of surface topography by determining RMS and Ra coefficients were performed by atomic force microscopy (AFM). In order to determine the optical properties of the films the UV-Visible spectroscope have been utilized. Current - voltage characteristics were employed to determine the basic photovoltaic parameters using a dedicated device.The paper describes the influence of the individual components sharing the bulk heterojunction on its structure, optical properties and morphology of surface. In addition it allows for linking active layers properties with the parameters of the photovoltaic cells. The obtained results suggest the possibility of developing the utilized materials and technology in the further works on photovoltaic structures.

scholarly journals Polycaprolactone-Based Mimetic Antimicrobial Peptide Copolymers Vesicles as an Effective Drug-Carrier for Cancer Therapy

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1783 ◽  
Author(s):  
Yusheng Qian ◽  
Xinyu Zhou ◽  
Jing He ◽  
Chuncai Zhou
Keyword(s):  
Cancer Therapy ◽  
Drug Release ◽  
Antimicrobial Peptide ◽  
Drug Carrier ◽  
Uniform Size ◽  
Vesicular Structure ◽  
Transmission Electron ◽  
Low Concentrations ◽  
Carrier Systems

A novel series of amphiphilic mimicking antimicrobial peptide copolymers PCL16-b-Kn can assemble in water to form uniform vesicles. Transmission electron microscopy was used to observe the vesicular structure of the nanoparticles, and dynamic light scattering revealed their uniform size and narrow dispersion. Critical vesiculation concentrations were also tested, revealing that these vesicles can exist at low concentrations. Furthermore, in vitro and intracellular drug release of doxorubicin(DOX)-vesicles were conducted. These vesicles could encapsulate DOX and achieve efficient intracellular drug release. Overall, these copolymer vesicles exhibit potential application value as multifunctional drug-carrier systems with antibacterial capability in cancer therapy.

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