Electric charge of nanopatterned silica surfaces

2019 ◽  
Vol 21 (14) ◽  
pp. 7576-7587 ◽  
Author(s):  
H. Gokberk Ozcelik ◽  
Murat Barisik
Keyword(s):  
Surface Charge ◽  
Flat Surface ◽  
Ionic Concentration ◽  
Surface Pattern ◽  
Surface Charges ◽  
Local Surface ◽  
Silica Surfaces ◽  
Pattern Size ◽  
Theoretical Predictions ◽  
Surface Patterns

The surface charge density of a nanopatterned silica decreased at the pits but increased at the tips of surface patterns. For a case of self-repeating surface structures, the average of local surface charges becomes lower than the theoretical predictions. Our phenomenological model developed as an extension to the existing flat surface theory predicts the average surface charge on a nanopatterned surface as a function of surface pattern size, ionic concentration and pH.

Full Simulation Study of UV Photodetectors Based on Pn Junctions in Silicon Carbide

2013 ◽  
Vol 740-742 ◽  
pp. 1018-1023
Author(s):  
Laurent Ottaviani ◽  
Wilfried Vervisch ◽  
Stephane Biondo ◽  
Olivier Palais
Keyword(s):  
Current Density ◽  
Flat Surface ◽  
Uv Light ◽  
Surface Pattern ◽  
Patterned Surfaces ◽  
Uv Photodetectors ◽  
Optical Generation ◽  
Surface Patterns ◽  
Pn Junctions ◽  
Surface Length

This paper deals with optical and electrical simulations of 4H-SiC UV-Photodetectors based on pn junctions. The simulations are performed under the UV light, with wavelengths varying between 200 nm and 300 nm. Under reverse bias, the simulation results point out the influence of surface patterns on the current density. The studied structures of the patterns consist in a semicircle with or without a flat surface. The patterned surfaces are parametrized according to the semicircle radius R and the flat surface length L. We show that the optical absorption strongly depends on these parameters, giving a maximum value whatever the wavelength with R = 100 nm and L = 0 nm (no flat surface). However, to optimise the carrier harvest, it is important for the space charge region to be situated in a zone where the optical generation is high. This study shows that the photodetector current density increases within three orders of magnitude (from 9x10-14 A.cm-2 to 3x10-10 A.cm-2), by using the specific surface pattern given above.

Effect of Surface Patterning on the Adhesive Friction

2012 ◽  
Author(s):  
Ola H. Rashwan ◽  
Vesselin Stoilov ◽  
Ahmet T. Alpas ◽  
Ariel R. Guerrero
Keyword(s):  
Adhesion Force ◽  
Adhesive Force ◽  
Surface Pattern ◽  
Tribological Behaviour ◽  
Pattern Density ◽  
Pattern Size ◽  
Hardened Tool Steel ◽  
Surface Patterns ◽  
Different Diameters ◽  
The Impact

Tribological properties play an important role in many applications that require low adhesion or non sticking surfaces; therefore, understanding the effect of the surface morphology on adhesion can allow for improved surfaces to be created. In the last 10 years, researchers have paid attention to the impact of the surface roughness on the tribological behaviour. As a result the idea of surface pattering or texturing has emerged as a mean of controlling the friction and adhesion between contacting surfaces. In this study, the effect of the different surface patterns with specifically selected parameters, such as the pattern size, and pattern density on the adhesion force which is measured by Atomic Force Microscope (AFM) is thoroughly investigated. First, micro laser dimples of different diameters’ (D’s) of 5, 10 and 20 μm are fabricated on air hardened tool steel samples using High quality–high power CuBr vapour laser. The distance (L), between the centers of two neighbouring circular dimples, were set to different values of 5, 10, 20, 40 and 80 μm. The AFM tip is modified so that the effect of the patterning on the adhesive force can be captured. A customized micro fabricated polystyrene particle of 120 μm in diameter is used as a tip attachment to the end of calibrated silicon nitride cantilever. The pull-off force versus displacement curves are recorded and used to estimate the average adhesion force for each surface pattern. It has been observed that selected surface patterns significantly decrease the adhesive forces compared to a flat surface. The ratio D/L, which represents the pattern density or the complement of the contact area establishes a well-defined trend of decrease of the adhesion force as D/L increases.

scholarly journals Surface charges toolkit for gravity

2020 ◽  
Vol 29 (06) ◽  
pp. 2050040
Author(s):  
Ernesto Frodden ◽  
Diego Hidalgo
Keyword(s):  
Surface Charge ◽  
Gauge Theories ◽  
Differential Forms ◽  
Gravity Theory ◽  
Surface Charges ◽  
Local Surface ◽  
Yang Mills ◽  
Gravity Theories ◽  
Chern Simons ◽  
Matter Fields

These notes provide a detailed catalog of surface charge formulas for different classes of gravity theories. The present catalog reviews and extends the existing literature on the topic. Part of the focus is on reviewing the method to compute quasi-local surface charges for gauge theories in order to clarify conceptual issues and their range of applicability. Many surface charge formulas for gravity theories are expressed in metric, tetrads-connection, Chern–Simons connection, and even BF variables. For most of them, the language of differential forms is exploited and contrasted with the more popular metric components language. The gravity theory is coupled with matter fields as scalar, Maxwell, Skyrme, Yang–Mills, and spinors. Furthermore, three examples with ready-to-download notebook codes, show the method in full action. Several new results are highlighted through the notes.

scholarly journals The Role of Crystalline Orientation in the Formation of Surface Patterns on Solids Irradiated with Femtosecond Laser Double Pulses

2020 ◽  
Vol 10 (24) ◽  
pp. 8811
Author(s):  
George D. Tsibidis ◽  
Luc Museur ◽  
Andrei Kanaev
Keyword(s):  
Carrier Density ◽  
Fluid Transport ◽  
Temperature Drop ◽  
Thermal Response ◽  
Surface Pattern ◽  
Temporal Separation ◽  
Pulse Separation ◽  
Theoretical Predictions ◽  
Surface Patterns

A theoretical investigation of the underlying ultrafast processes upon irradiation of rutile TiO2 of (001) and (100) surface orientation with femtosecond (fs) double pulsed lasers was performed in ablation conditions, for which, apart from mass removal, phase transformation and surface modification of the heated solid were induced. A parametric study was followed to correlate the transient carrier density and the produced lattice temperature with the laser fluence, pulse separation and the induced damage. The simulations showed that both temporal separation and crystal orientation influence the surface pattern, while both the carrier density and temperature drop gradually to a minimum value at temporal separation equal to twice the pulse separation that remain constant at long delays. Carrier dynamics, interference of the laser beam with the excited surface waves, thermal response and fluid transport at various pulse delays explained the formation of either subwavelength or suprawavelength structures. The significant role of the crystalline anisotropy is illustrated through the presentation of representative experimental results correlated with the theoretical predictions.

scholarly journals Water Dynamics in Hydrated Carboxylated Cellulose Nanofibril Membranes

2019 ◽  
Author(s):  
Shun Yu ◽  
Valentina Guccini ◽  
Franz Demmel ◽  
Germán Salazar-Alvarez
Keyword(s):  
Surface Charge ◽  
Network Formation ◽  
Water Movement ◽  
Polymer Electrolyte Membrane ◽  
Cellulose Nanofibrils ◽  
Bulk Water ◽  
Water Dynamics ◽  
Surface Charges ◽  
Tempo Oxidation ◽  
Elastic Neutron

Cellulose nanofibrils (CNF) are a class of materials with good mechanical properties, surface functionality and bio-/environmental friendliness. They have been used in many applications as loading material or function materials, where water-cellulose interaction determines the materials performance. Especially, CNF with carboxylated groups can be used as the separation membrane in polymer electrolyte membrane fuel cell. The water dynamics is closely related to the proton conductivity. The Non-destructive quasi-elastic neutron scattering (QENS) is used to characterized water movement in hydrated membrane made of CNF prepared by TEMPO-oxidation with different surface charges. However, neither surface charge nor the nanoconfinement due to membrane swelling has large impact on water dynamics mechanism. A slow diffusive motion is found with the diffusion coefficient close to bulk water and that in hydrated Nafion membrane regardless the surface charge, while a fast motion is rather localized with a correlation time increasing as temperature increase, which might related to the hydrogen bond network formation between water and CNF.

scholarly journals Local and correlated studies of humidity-mediated ferroelectric thin film surface charge dynamics

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Iaroslav Gaponenko ◽  
Loïc Musy ◽  
Neus Domingo ◽  
Nicolas Stucki ◽  
Albert Verdaguer ◽  
...  
Keyword(s):  
Surface Charge ◽  
Dictionary Learning ◽  
Film Surface ◽  
Ferroelectric Thin Film ◽  
Microscopy Study ◽  
Lateral Spread ◽  
Surface Charges ◽  
Kelvin Probe ◽  
Sensing Applications ◽  
Reaction Diffusion Model

AbstractElectrochemical phenomena in ferroelectrics are of particular interest for catalysis and sensing applications, with recent studies highlighting the combined role of the ferroelectric polarisation, applied surface voltage and overall switching history. Here, we present a systematic Kelvin probe microscopy study of the effect of relative humidity and polarisation switching history on the surface charge dissipation in ferroelectric Pb(Zr0.2Ti0.8)O3 thin films. We analyse the interaction of surface charges with ferroelectric domains through the framework of physically constrained unsupervised machine learning matrix factorisation, Dictionary Learning, and reveal a complex interplay of voltage-mediated physical processes underlying the observed signal decays. Additional insight into the observed behaviours is given by a Fitzhugh–Nagumo reaction–diffusion model, highlighting the lateral spread and charge passivation process contributors within the Dictionary Learning analysis.

Surface Replication and Structural Development in Micromolding for Micro/Nanocomposites

2007 ◽  
Author(s):  
H. Ito ◽  
K. Kazama ◽  
T. Kikutani
Keyword(s):  
Laser Scanning ◽  
Hexagonal Boron Nitride ◽  
Laser Scanning Microscopy ◽  
Surface Pattern ◽  
Confocal Laser ◽  
Order Structure ◽  
Structural Development ◽  
Molded Parts ◽  
Surface Patterns ◽  
Micro Features

Micromolding with micro-scale surface features of hexagonal boron nitride (h-BN) / polypropylene (PP) composites with different h-BN component was performed to improve molded parts’ heat diffusivity and processability. Effects of h-BN content and process parameters on processability, higher-order structure, and microscale surface patterns of molded parts were analyzed using SEM, WAXD, SPM, and confocal laser scanning microscopy. The replication ratio of the microscale surface pattern and flow length of composite molded parts was improved by compounding the h-BN filler. The replication ratio of the microscale surface pattern near the flow end became greater than 1.0 because of deformation of surface patterns during de-molding. The replication ratio and shape of surface patterns of molded parts were improved with the increase of the h-BN component. The h-BN platelet oriented inside surface micro-features; skin-shear-core structures were well observed in the molded parts.

Surface Patterning of Stainless Steel in Prevention of Fouling in Heat Transfer Equipment

2013 ◽  
Vol 762 ◽  
pp. 493-500 ◽  
Author(s):  
Tiina M. Pääkkönen ◽  
Ulla Ojaniemi ◽  
Markus Riihimäki ◽  
Esa Muurinen ◽  
Carey J. Simonson ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Thermal Conditions ◽  
Surface Patterning ◽  
Surface Pattern ◽  
Stainless Steel Surface ◽  
Cfd Modelling ◽  
Carbonate Solutions ◽  
Wide Range ◽  
Surface Patterns

Fouling of surfaces is a major challenge in design and operation of many industrial heat transfer equipment. Fouling causes significant energy, material and production losses, which increase the environmental impact and decrease economic profitability of processes. Even small improvements in prevention of fouling would lead to significant savings in a wide range of heat transfer applications. In this study, crystallization fouling of aqueous calcium carbonate solutions on a heated stainless steel surface is used to investigate the prevention of fouling in heat transfer equipment by physical surface modifications. Fouling behaviour of different surface patterns are studied experimentally in a laboratory scale fouling test apparatus. CFD modelling is used to study hydrodynamic and thermal conditions near surfaces with different patterns. In addition, the effect of surface pattern on the removal of particles is studied numerically. Surface patterning is found to affect the hydrodynamic and thermal conditions near the wall, and therefore to change the conditions for fouling layer build-up and removal, when compared to a flat heat transfer surface. The most promising surface pattern includes curved shapes, and it seems to create flow conditions in which improved convective heat transfer decreases the driving force for crystallization fouling. In addition, curved surfaces increase the shear forces at the wall, which prevents adhesion of the foulants to the surface and increases resuspension.

scholarly journals Conduction through the Inward Rectifier Potassium Channel, Kir2.1, Is Increased by Negatively Charged Extracellular Residues

2005 ◽  
Vol 125 (5) ◽  
pp. 493-503 ◽  
Author(s):  
Nazzareno D'Avanzo ◽  
Hee Cheol Cho ◽  
Illya Tolokh ◽  
Roman Pekhletski ◽  
Igor Tolokh ◽  
...  
Keyword(s):  
Surface Charge ◽  
Single Channel ◽  
Molecular Model ◽  
Chinese Hamster ◽  
Fluctuation Analysis ◽  
Channel Measurements ◽  
Surface Charges ◽  
Charge Effects ◽  
Current Decay ◽  
Inward Rectifier Potassium Channel

Ion channel conductance can be influenced by electrostatic effects originating from fixed “surface” charges that are remote from the selectivity filter. To explore whether surface charges contribute to the conductance properties of Kir2.1 channels, unitary conductance was measured in cell-attached recordings of Chinese hamster ovary (CHO) cells transfected with Kir2.1 channels over a range of K+ activities (4.6–293.5 mM) using single-channel measurements as well as nonstationary fluctuation analysis for low K+ activities. K+ ion concentrations were shown to equilibrate across the cell membrane in our studies using the voltage-sensitive dye DiBAC4(5). The dependence of γ on the K+ activity (aK) was fit well by a modified Langmuir binding isotherm, with a nonzero intercept as aK approaches 0 mM, suggesting electrostatic surface charge effects. Following the addition of 100 mM N-methyl-d-glucamine (NMG+), a nonpermeant, nonblocking cation or following pretreatment with 50 mM trimethyloxonium (TMO), a carboxylic acid esterifying agent, the γ–aK relationship did not show nonzero intercepts, suggesting the presence of surface charges formed by glutamate or aspartate residues. Consistent with surface charges in Kir2.1 channels, the rates of current decay induced by Ba2+ block were slowed with the addition of NMG or TMO. Using a molecular model of Kir2.1 channels, three candidate negatively charged residues were identified near the extracellular mouth of the pore and mutated to cysteine (E125C, D152C, and E153C). E153C channels, but not E125C or D152C channels, showed hyperbolic γ–aK relationships going through the origin. Moreover, the addition of MTSES to restore the negative charges in E53C channels reestablished wild-type conductance properties. Our results demonstrate that E153 contributes to the conductance properties of Kir2.1 channels by acting as a surface charge.

Role of Si(100) Surface Patterns in the Phase Separation of Cu/Sn Thin Films

2001 ◽  
Vol 672 ◽  
Author(s):  
Qin Hu ◽  
Martin Zinke–Allmang ◽  
Ian V. Mitchell
Keyword(s):  
Thin Film ◽  
Thermal Decomposition ◽  
Phase Separation ◽  
Ex Situ ◽  
Surface Pattern ◽  
Length Scale ◽  
Thermal Decomposition Process ◽  
Surface Patterns ◽  
Initial Pattern

ABSTRACTWe report on the competitive phase separation of copper and tin thin film deposits on a pre–patterned Si(100) surface. The initial pattern on Si(100) was achieved through a thermal decomposition process of an ex–situ grown oxide film. Copper and tin phase separation on silicon is a competitive process with Cu forming preferrably silicide. Sn is observed to cover the silicide clusters when present in a sufficient amount. The pre–patterning of the surface introduces a new length scale in the problem. Our data suggest that this length scale plays a role while the clustering (ripening) length scale is of the same order, i.e., during nucleation and the early phase separation, but that both length scales become independent once the length scale of ripening significantly exceeds the length scale of the surface pattern.

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