scholarly journals The Electronic Properties of Extended Defects in SrTiO3—A Case Study of a Real Bicrystal Boundary

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 665 ◽  
Author(s):  
Christian Rodenbücher ◽  
Dominik Wrana ◽  
Thomas Gensch ◽  
Franciszek Krok ◽  
Carsten Korte ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Boundary Region ◽  
Thermal Reduction ◽  
Fluorescence Lifetime Imaging ◽  
Extended Defects ◽  
Force Microscopy ◽  
Ab Initio Simulations ◽  
Complementary Method ◽  
Inhomogeneous Properties ◽  
The Impact

This study investigates the impact of extended defects such as dislocations on the electronic properties of SrTiO3 by using a 36.8° bicrystal as a model system. In order to evaluate the hypothesis that dislocations can serve as preferential reduction sites, which has been proposed in the literature on the basis of ab initio simulations, as well as on experiments employing local-conductivity atomic force microscopy (LC-AFM), detailed investigations of the bicrystal boundary are conducted. In addition to LC-AFM, fluorescence lifetime imaging microscopy (FLIM) is applied herein as a complementary method for mapping the local electronic properties on the microscale. Both techniques confirm that the electronic structure and electronic transport in dislocation-rich regions significantly differ from those of undistorted SrTiO3. Upon thermal reduction, a further confinement of conductivity to the bicrystal boundary region was found, indicating that extended defects can indeed be regarded as the origin of filament formation. This leads to the evolution of inhomogeneous properties of defective SrTiO3 on the nano- and microscales.

Formation and Properties of Schottky Diodes on 4H-SiC after High Temperature Annealing with Graphite Encapsulation

2006 ◽  
Vol 527-529 ◽  
pp. 915-918 ◽  
Author(s):  
Y. Wang ◽  
M.K. Mikhov ◽  
B.J. Skromme
Keyword(s):  
High Temperature ◽  
Ideality Factor ◽  
Schottky Diodes ◽  
Extended Defects ◽  
High Temperature Annealing ◽  
Force Microscopy ◽  
Atomic Force ◽  
Current Voltage ◽  
Encapsulation Method ◽  
The Impact

The impact of high temperature annealing using graphite encapsulation (formed by baking photoresist) on the electrical properties of Ni Schottky diodes formed on the annealed surfaces is studied. The surface morphology is also characterized by atomic force microscopy (AFM). Annealing for 10 minutes at temperatures up to 1800 °C with graphite encapsulation actually reduces the high-current ideality factor of the diodes while raising the current-voltage barrier height (linearly extrapolated to unity ideality factor) from 1.453 V to 1.67-1.73 V. Excess leakage current occurs only in a subset of diodes, which are believed to be affected by extended defects. The AFM images show no significant surface roughening, and the graphite can be removed after processing. This encapsulation method is found to be highly effective in preserving the electronic properties of the surface during high temperature annealing.

scholarly journals Quantitative determination of atomic buckling of silicene by atomic force microscopy

2019 ◽  
Vol 117 (1) ◽  
pp. 228-237 ◽  
Author(s):  
Rémy Pawlak ◽  
Carl Drechsel ◽  
Philipp D’Astolfo ◽  
Marcin Kisiel ◽  
Ernst Meyer ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Electronic Properties ◽  
Density Functional ◽  
Local Symmetry ◽  
Quantum Spin ◽  
Atomic Scale ◽  
Extended Defects ◽  
Force Microscopy ◽  
Atomic Force ◽  
Structural And Electronic Properties

The atomic buckling in 2D “Xenes” (such as silicene) fosters a plethora of exotic electronic properties such as a quantum spin Hall effect and could be engineered by external strain. Quantifying the buckling magnitude with subangstrom precision is, however, challenging, since epitaxially grown 2D layers exhibit complex restructurings coexisting on the surface. Here, we characterize using low-temperature (5 K) atomic force microscopy (AFM) with CO-terminated tips assisted by density functional theory (DFT) the structure and local symmetry of each prototypical silicene phase on Ag(111) as well as extended defects. Using force spectroscopy, we directly quantify the atomic buckling of these phases within 0.1-Å precision, obtaining corrugations in the 0.8- to 1.1-Å range. The derived band structures further confirm the absence of Dirac cones in any of the silicene phases due to the strong Ag-Si hybridization. Our method paves the way for future atomic-scale analysis of the interplay between structural and electronic properties in other emerging 2D Xenes.

scholarly journals Extracellular Vesicles Analysis in the COVID-19 Era: Insights on Serum Inactivation Protocols towards Downstream Isolation and Analysis

Cells ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 544
Author(s):  
Roberto Frigerio ◽  
Angelo Musicò ◽  
Marco Brucale ◽  
Andrea Ridolfi ◽  
Silvia Galbiati ◽  
...  
Keyword(s):  
Extracellular Vesicles ◽  
Analytical Techniques ◽  
Heat Inactivation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Droplet Pcr ◽  
Detergent Treatment ◽  
Routine Procedures ◽  
The Impact ◽  
Mirna Content

Since the outbreak of the COVID-19 crisis, the handling of biological samples from confirmed or suspected SARS-CoV-2-positive individuals demanded the use of inactivation protocols to ensure laboratory operators’ safety. While not standardized, these practices can be roughly divided into two categories, namely heat inactivation and solvent-detergent treatments. These routine procedures should also apply to samples intended for Extracellular Vesicles (EVs) analysis. Assessing the impact of virus-inactivating pre-treatments is therefore of pivotal importance, given the well-known variability introduced by different pre-analytical steps on downstream EVs isolation and analysis. Arguably, shared guidelines on inactivation protocols tailored to best address EVs-specific requirements will be needed among the analytical community, yet deep investigations in this direction have not yet been reported. We here provide insights into SARS-CoV-2 inactivation practices to be adopted prior to serum EVs analysis by comparing solvent/detergent treatment vs. heat inactivation. Our analysis entails the evaluation of EVs recovery and purity along with biochemical, biophysical and biomolecular profiling by means of a set of complementary analytical techniques: Nanoparticle Tracking Analysis, Western Blotting, Atomic Force Microscopy, miRNA content (digital droplet PCR) and tetraspanin assessment by microarrays. Our data suggest an increase in ultracentrifugation (UC) recovery following heat treatment; however, it is accompanied by a marked enrichment in EVs-associated contaminants. On the other hand, solvent/detergent treatment is promising for small EVs (<150 nm range), yet a depletion of larger vesicular entities was detected. This work represents a first step towards the identification of optimal serum inactivation protocols targeted to EVs analysis.

scholarly journals Dye Separation and Antibacterial Activities of Polyaniline Thin Film-Coated Poly(phenyl sulfone) Membranes

Membranes ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 25
Author(s):  
Javed Alam ◽  
Arun Kumar Shukla ◽  
Mohammad Azam Ansari ◽  
Fekri Abdulraqeb Ahmed Ali ◽  
Mansour Alhoshan
Keyword(s):  
Zeta Potential ◽  
Surface Properties ◽  
Antibacterial Activities ◽  
Pani Film ◽  
Force Microscopy ◽  
Water Permeation ◽  
Membrane Pores ◽  
Membrane Performance ◽  
Phenyl Sulfone ◽  
The Impact

We fabricated a nanofiltration membrane consisting of a polyaniline (PANI) film on a polyphenylsulfone (PPSU) substrate membrane. The PANI film acted as a potent separation enhancer and antimicrobial coating. The membrane was analyzed via scanning electron microscopy and atomic force microscopy to examine its morphology, topography, contact angle, and zeta potential. We aimed to investigate the impact of the PANI film on the surface properties of the membrane. Membrane performance was then evaluated in terms of water permeation and rejection of methylene blue (MB), an organic dye. Coating the PPSU membrane with a PANI film imparted significant advantages, including finely tuned nanometer-scale membrane pores and tailored surface properties, including increased hydrophilicity and zeta potential. The PANI film also significantly enhanced separation of the MB dye. The PANI-coated membrane rejected over 90% of MB with little compromise in membrane permeability. The PANI film also enhanced the antimicrobial activity of the membrane. The bacteriostasis (BR) values of PANI-coated PPSU membranes after six and sixteen hours of incubation with Escherichia coli were 63.5% and 95.2%, respectively. The BR values of PANI-coated PPSU membranes after six and sixteen hours of incubation with Staphylococcus aureus were 70.6% and 88.0%, respectively.

scholarly journals The Impact of Vibrational Entropy on the Segregation of Cu to Antiphase Boundaries in Fe3Al

2021 ◽  
Vol 7 (8) ◽  
pp. 108
Author(s):  
Martin Friák ◽  
Miroslav Černý ◽  
Mojmír Šob
Keyword(s):  
Magnetic Moments ◽  
Energy Difference ◽  
Extended Defects ◽  
Vibrational Entropy ◽  
Phonon Modes ◽  
Antiphase Boundaries ◽  
Related Energy ◽  
Quantum Mechanical Study ◽  
Nonlinear Trends ◽  
The Impact

We performed a quantum mechanical study of segregation of Cu atoms toward antiphase boundaries (APBs) in Fe3Al. The computed concentration of Cu atoms was 3.125 at %. The APBs have been characterized by a shift of the lattice along the ⟨001⟩ crystallographic direction. The APB energy turns out to be lower for Cu atoms located directly at the APB interfaces and we found that it is equal to 84 mJ/m2. Both Cu atoms (as point defects) and APBs (as extended defects) have their specific impact on local magnetic moments of Fe atoms (mostly reduction of the magnitude). Their combined impact was found to be not just a simple sum of the effects of each of the defect types. The Cu atoms are predicted to segregate toward the studied APBs, but the related energy gain is very small and amounts to only 4 meV per Cu atom. We have also performed phonon calculations and found all studied states with different atomic configurations mechanically stable without any soft phonon modes. The band gap in phonon frequencies of Fe3Al is barely affected by Cu substituents but reduced by APBs. The phonon contributions to segregation-related energy changes are significant, ranging from a decrease by 16% at T = 0 K to an increase by 17% at T = 400 K (changes with respect to the segregation-related energy difference between static lattices). Importantly, we have also examined the differences in the phonon entropy and phonon energy induced by the Cu segregation and showed their strongly nonlinear trends.

Structuring of Silicon Wafer Surfaces on the Sub-100 nm Scale by Hydrogen Plasma Treatments

2003 ◽  
Vol 788 ◽  
Author(s):  
R. Job ◽  
Y. Ma ◽  
A. G. Ulyashin
Keyword(s):  
Hydrogen Plasma ◽  
Structural Defects ◽  
Process Conditions ◽  
Force Microscopy ◽  
Czochralski Silicon ◽  
Atomic Force ◽  
Nano Structures ◽  
Plasma Treatments ◽  
The Impact ◽  
Wafer Surfaces

ABSTRACTHydrogen plasma treatments applied on standard Czochralski silicon (Cz Si) wafers cause a structuring of the surface regions on the sub-100 nm scale, i.e. a thin ‘nano-structured’ Si layer is created up to a depth of ∼ 150 nm. The formation of the ‘nano-structures’ and their evolution in dependence on the process conditions was studied. The impact of post-hydrogenation annealing on the morphology of the structural defects was studied up to 1200 °C. The H-plasma treated and annealed samples were analyzed at surface and sub-surface regions by scanning electron microscopy (SEM), atomic force microscopy (AFM), and μ-Raman spectroscopy.

Asymptotically matched sheath and presheath in a dense plasma

1998 ◽  
Vol 59 (3) ◽  
pp. 505-536 ◽  
Author(s):  
LINDSEY D. THORNHILL ◽  
PRATEEN V. DESAI
Keyword(s):  
Rapid Change ◽  
Debye Length ◽  
Mean Free Path ◽  
Boundary Region ◽  
Surface Erosion ◽  
Leading Order ◽  
Power Flux ◽  
Temperature Plasma ◽  
Recombination Length ◽  
The Impact

Asymptotically matched solutions for electron and ion density, electron and ion velocity, and electric potential are obtained in the boundary region of a dense low-temperature plasma adjacent to perfectly absorbing walls – walls that absorb, without reflection, incident electrons and ions. Leading-order composite solutions, valid throughout the boundary region, are constructed from solutions in three subdomains distinguished by different physical length scales: the geometric length, the ion mean free path and the Debye length. The composite solutions are used to assess the impact of electron–ion recombination in the ionization nonequilibrium region on sheath and presheath profiles, and on quantities evaluated at the wall. While, at leading order, the velocity profiles throughout the boundary region are not influenced by recombination, the density and potential profiles are significantly altered when recombination is included. These results show that the region of rapid change in these profiles lies closer to the wall when recombination is explicitly included in the model. The influence of recombination on the presheath potential, and consequently the wall potential, is found to scale as the natural logarithm of the recombination length. The broadening of the density profile results in a larger flux of ions accelerating through the sheath and impacting on the wall. The influence of recombination on the ion power flux to the wall is found to scale with the inverse recombination length. This scaling influences the prediction of surface erosion rates in technological applications that utilize these plasmas.

Theoretical modeling of growth processes, extended defects, and electronic properties of III-nitride semiconductor nanostructures

2011 ◽  
Vol 248 (8) ◽  
pp. 1837-1852 ◽  
Author(s):  
Liverios Lymperakis ◽  
Hazem Abu-Farsakh ◽  
Oliver Marquardt ◽  
Tilmann Hickel ◽  
Jörg Neugebauer
Keyword(s):  
Electronic Properties ◽  
Semiconductor Nanostructures ◽  
Theoretical Modeling ◽  
Extended Defects ◽  
Growth Processes ◽  
Nitride Semiconductor

scholarly journals Deswelling Induced Morphological Changes in Dual pH and Temperature Responsive Ultra-Low Crosslinked Poly (N-Isopropyl Acrylamide)-Co-Acrylic Acid Microgels

2018 ◽  
Author(s):  
Molla Islam ◽  
Maddie Tumbarello ◽  
Andrew Lyon
Keyword(s):  
Light Scattering ◽  
Acrylic Acid ◽  
Morphological Changes ◽  
Scattering Data ◽  
Ionization State ◽  
Force Microscopy ◽  
Temperature Responsive ◽  
Atomic Force ◽  
Isopropyl Acrylamide ◽  
The Impact

<div>We demonstrated the deswelling induced morphological change in dual pH and Temperature responsive ultra-low crosslinked Poly (N-isopropyl acrylamide)-co-acrylic acid microgels. The responsivity with pH and temperature were studied by light scattering and atomic force microscopy. Light scattering data suggest that at pH 4.5 the microgels undergo multiple transitions associated with collapse of pNIPAm-rich segments and repulsion between the AAc-rich segments. The evolution of punctate structures around the periphery or throughout the whole microgels at pH 4.5 and 6.5 respectively was revealed by AFM, further illustrating the heterogeneous deswelling present in the ionized copolymer microgels.</div><div>The impact of this study and understanding how ionization state of copolymer dictates the overall structural properties of microgels will widen our understanding for their applications in biotechnology</div><div><b><br></b></div>

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