scholarly journals FORMATION OF THE TWO-DIMENSIONAL ELECTRON GAS (2DEG) IN THE STRUCTURE WITH TWO AlxGa1-xN/GaN/AlуGa1-уN BARRIER LAYERS

2020 ◽  
pp. 4-16
Author(s):  
A.N. Maksimov
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Barrier Layer ◽  
Surface Charge Density ◽  
Surface Concentration ◽  
Barrier Layers ◽  
Noticeable Increase ◽  
Positive Side ◽  
Dimensional Electron Gas ◽  
The Relationship

This article is dedicated to the study of AlxGa1-xN/GaN/AlуGa1-уN heterostructures and spontaneous and piezoelectric polarizations, which induces 2DEG. In this research the surface charge density, the surface concentration of carriers in the channel and the relationship between the amount of Al molar fractions in upper and lower barrier layers and the surface charge density were determined. Change in the concentration of Al mole fractions in the upper barrier layer from 15 to 40, causes noticeable increase in the surface concentration of carriers ns(x). Change in the concentration of Al mole fractions in the lower barrier layer from 0.05 to 0.12, causes noticeable decrease in the surface concentration of ns carriers. The features of high-voltage HEMT with two barrier layers were considered. The introduction of the second barrier layer leads to a better electron confinement in the GaN channel, but at the same time, the maximum carrier density (2DEG) in the channel decreases and the voltage threshold shifts to the positive side.

scholarly journals Slip length and structure of liquid water flowing past atomistic smooth charged walls

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Xinran Geng ◽  
Miao Yu ◽  
Wei Zhang ◽  
Qiwei Liu ◽  
Xiaopeng Yu ◽  
...  
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Interaction Energy ◽  
Liquid Water ◽  
Surface Charge Density ◽  
Slip Length ◽  
Static Structure Factor ◽  
Charged Surface ◽  
Static Structure ◽  
The Relationship

AbstractIn this work, the slip behavior and structure of liquid water flowing between two charged solid planar walls were investigated using non-equilibrium molecular dynamics simulations. The upper and lower walls are positive and negative charged, respectively. It was shown that the slip length increases at smaller water-solid interaction energy and become smaller with increasing the surface charge density. At the largest surface charge density, the slip length nearly independent of the water-solid interaction energy. The relationship between the slip length and surface charge density and water-solid interaction energy was rationalized by considering the static structure factor of liquid water. Interestingly, the positive charged surface induces less ordering structure and larger slip at the small surface charge density than that by the negative charged surface. While, at large surface charge density, the opposite correlation is observed. Furthermore, we find that the relationship between the slip length and the normalized main peak of static structure factor collapses onto a single curve for different water-solid interaction energies and surface charge densities. The results of the present work open perspectives for modeling complex systems with combined effects of surface charge and wettability.

scholarly journals Equilibria in DPPC-Diosgenin and DPPC-Diosgenin Acetate Bilayer Lipid Membranes: Interfacial Tension and Microelectrophoretic Studies

Coatings ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 368 ◽  
Author(s):  
Katarzyna Karwowska ◽  
Ewelina Skrodzka ◽  
Joanna Kotyńska ◽  
Aneta D. Petelska
Keyword(s):  
Interfacial Tension ◽  
Charge Density ◽  
Surface Charge ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Surface Charge Density ◽  
Surface Concentration ◽  
Membrane Systems ◽  
Mobility Data ◽  
Model Lipid Membranes

Interactions between components of model lipid membranes (spherical lipid bilayers and liposomes) are investigated here. Parameters characterizing equilibria in the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)-diosgenin (Dio) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)-diosgenin acetate (DAc) membrane systems have been determined. The interfacial tension measurement of spherical lipid bilayers was based on the Young-Laplace’s equation using a homemade computer-controlled device. We assume a 1:1 complex in the DPPC-Dio and DPPC-DAc membrane systems. The parameters A 3 − 1 , the surface concentration of lipid membranes formed from these complexes, γ 3 , the interfacial tension of such membranes, and, K, the constant stability of these complexes were calculated. Microelectrophoresis was used for examinations of the surface charge density of lipid membranes. The values were obtained here from electrophoretic mobility data applying Smoluchowsky’s equation. The effect of pH (pH ranged of 2 to 10) on the electrolyte solution and the compositions of the membranes was analyzed. The obtained results indicate that the modification of DPPC membranes with both Dio and DAc causes changes in surface charge density values and shifts of the isoelectric point.

scholarly journals Mapping Surface Charge Distribution of Single-Cell via Charged Nanoparticle

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1519
Author(s):  
Leixin Ouyang ◽  
Rubia Shaik ◽  
Ruiting Xu ◽  
Ge Zhang ◽  
Jiang Zhe
Keyword(s):  
Cell Surface ◽  
Charge Density ◽  
Surface Charge ◽  
Charge Distribution ◽  
Surface Charge Density ◽  
Single Cells ◽  
Fluorescent Light ◽  
Fluorescent Nanoparticles ◽  
Cell Surface Charge ◽  
Surface Charge Distribution

Many bio-functions of cells can be regulated by their surface charge characteristics. Mapping surface charge density in a single cell’s surface is vital to advance the understanding of cell behaviors. This article demonstrates a method of cell surface charge mapping via electrostatic cell–nanoparticle (NP) interactions. Fluorescent nanoparticles (NPs) were used as the marker to investigate single cells’ surface charge distribution. The nanoparticles with opposite charges were electrostatically bonded to the cell surface; a stack of fluorescence distribution on a cell’s surface at a series of vertical distances was imaged and analyzed. By establishing a relationship between fluorescent light intensity and number of nanoparticles, cells’ surface charge distribution was quantified from the fluorescence distribution. Two types of cells, human umbilical vein endothelial cells (HUVECs) and HeLa cells, were tested. From the measured surface charge density of a group of single cells, the average zeta potentials of the two types of cells were obtained, which are in good agreement with the standard electrophoretic light scattering measurement. This method can be used for rapid surface charge mapping of single particles or cells, and can advance cell-surface-charge characterization applications in many biomedical fields.

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