Analysis of Step-Velocity-Dependent Concentration of Magnesium in GaN Based on Burton−Cabrera−Frank Theory and Step-Edge Segregation Model

2021 ◽  
Author(s):  
Kazuhiro Mochizuki ◽  
Naoki Kaneda ◽  
Kentaro Hayashi ◽  
Hiroshi Ohta ◽  
Fumimasa Horikiri ◽  
...  
Keyword(s):  
Step Edge ◽  
Step Height ◽  
Magnesium Concentration ◽  
Velocity Dependence ◽  
Step Velocity

Abstract Based on Burton−Cabrera−Frank theory and the step-edge segregation model, we analyzed the reported difference in the sheet concentration of doped magnesium under naturally formed surface stripes on homo-epitaxially grown layers on a freestanding GaN substrate misoriented from a c-plane by 0.3°. By assuming the step height being equal to the peak-to-valley height of the surface stripes, we considered the growth steps on gently and sharply sloped surfaces to be supplied, respectively, from mixed dislocations and the misorientation from the c-plane. The step-velocity dependence of the magnesium concentration was reproduced with the reported magnesium diffusivity of 3×10−14 cm2s−1.

Step-edge segregation model for step-velocity dependences of carbon and oxygen concentrations in GaN layers grown on m-plane GaN

2020 ◽  
Vol 60 (1) ◽  
pp. 018002
Author(s):  
Kazuhiro Mochizuki ◽  
Fumimasa Horikiri ◽  
Hiroshi Ohta ◽  
Tomoyoshi Mishima
Keyword(s):  
Step Edge ◽  
Step Velocity ◽  
Oxygen Concentrations

scholarly journals Estimating Step Heights from Top-Down SEM Images

2019 ◽  
Vol 25 (4) ◽  
pp. 903-911 ◽  
Author(s):  
Kerim Tugrul Arat ◽  
Jens Bolten ◽  
Aernout Christiaan Zonnevylle ◽  
Pieter Kruit ◽  
Cornelis Wouter Hagen
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Semiconductor Industry ◽  
Step Edge ◽  
Step Height ◽  
Top Down ◽  
Sem Images ◽  
Force Microscopy ◽  
Atomic Force ◽  
Primary Electrons

AbstractScanning electron microscopy (SEM) is one of the most common inspection methods in the semiconductor industry and in research labs. To extract the height of structures using SEM images, various techniques have been used, such as tilting a sample, or modifying the SEM tool with extra sources and/or detectors. However, none of these techniques focused on extraction of height information directly from top-down images. In this work, using Monte Carlo simulations, we studied the relation between step height and the emission of secondary electrons (SEs) resulting from exposure with primary electrons at different energies. It is found that part of the SE signal, when scanning over a step edge, is determined by the step height rather than the geometry of the step edge. We present a way to quantify this, arriving at a method to determine the height of structures from top-down SEM images. The method is demonstrated on three different samples using two different SEM tools, and atomic force microscopy is used to measure the step height of the samples. The results obtained are in qualitative agreement with the results from the Monte Carlo simulations.

scholarly journals Orientation and Velocity Dependence of the Nonequilibrium Partition Coefficient

1995 ◽  
Vol 398 ◽  
Author(s):  
K.M. Beatty ◽  
K.A. Jackson
Keyword(s):  
Monte Carlo ◽  
Diffusion Coefficient ◽  
Partition Coefficient ◽  
Interface Velocity ◽  
Velocity Dependence ◽  
Step Velocity ◽  
Equilibrium Partition ◽  
Equilibrium Partition Coefficient ◽  
Solid Liquid Interface ◽  
Solid Liquid

ABSTRACTMonte Carlo simulations based on a Spin-1 Ising Model for binary alloys have been used to investigate the non-equilibrium partition coefficient (kneq ) as a function of solid-liquid interface velocity and orientation. In simulations of Si with a second component kneq is greater in the [111] direction than the [100] direction in agreement with experimental results reported by Aziz et al. The simulated partition coefficient scales with the square of the step velocity divided by the diffusion coefficient of the secondary component in the liquid.

Step-edge and kink segregation models for analysis of reported step-velocity dependences of carbon concentration in GaN

2020 ◽  
Vol 59 (6) ◽  
pp. 068001 ◽  
Author(s):  
Kazuhiro Mochizuki ◽  
Fumimasa Horikiri ◽  
Hiroshi Ohta ◽  
Tomoyoshi Mishima
Keyword(s):  
Carbon Concentration ◽  
Step Edge ◽  
Step Velocity

Effect of Nano-Scale Steps on the Microscopic Dynamic Contact Angle

2009 ◽  
Author(s):  
Junpei Doi ◽  
Takahiro Ito ◽  
Akira Hibi ◽  
Yutaka Kukita
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Solid Surface ◽  
Contact Line ◽  
Dynamic Contact ◽  
Immiscible Fluids ◽  
Step Edge ◽  
Dynamics Simulation ◽  
Step Height ◽  
Interaction Range

The motion of the contact line on a solid surface is strongly related with the contact angle there. In these days the relation between them has been revealed with the aid of molecular dynamics techniques; however, most of the studies on such phenomena have been made by assuming the solid surface to be molecularly planer and homogeneous, which condition is not necessarily satisfied in general industries. In this study, we conducted molecular dynamics simulation to investigate the behavior of dynamic contact line with a solid surface accompanied by steps parallel to the contact line. We applied a Couette flow geometry, where two immiscible fluids are confined between two parallel walls, one of which has the steps and is forced to move in the direction normal to the contact line. The behavior of the contact line and the variation in the contact angle were investigated by changing the height of the step from α0 to 4α0 where α0 is the lattice constant of the wall structure. It is shown that in case of the step height identical to α0, the contact line is temporary captured on the edge of the step. On the other hand with higher step the contact line is almost completely pinned on the step edge. The change in the contact angle by the pinning of the contact line on the step edge can be estimated by the macroscopic model as far as the step height is larger than the interaction range between molecules.

ABOLITION OF MAGNESIUM-INDUCED HYPOCALCAEMIA BY ACUTE THYRO-PARATHYROIDECTOMY IN THE CAT

1970 ◽  
Vol 64 (1) ◽  
pp. 150-158 ◽  
Author(s):  
S. Pors Nielsen
Keyword(s):  
Sodium Chloride ◽  
Flow Rate ◽  
Magnesium Chloride ◽  
Calcium Concentration ◽  
Plasma Calcium ◽  
Magnesium Concentration ◽  
Isotonic Sodium Chloride ◽  
Plasma Calcium Concentration ◽  
High Concentrations ◽  
Plasma Magnesium

ABSTRACT Intravenous infusion of isotonic magnesium chloride into young cats with a resultant mean plasma magnesium concentration of 7.7 meq./100 g protein was followed by a significant lowering of the plasma calcium concentration in 90 minutes. The rate of decrease of plasma calcium is consistent with the hypothesis that calcitonin is released by magnesium in high concentrations. There was no decrease in the plasma calcium concentration in cats of the same weight thyroparathyroidectomized 60 min before an identical magnesium chloride infusion or an infusion of isotonic sodium chloride at the same flow rate. The hypercalciuric effect of magnesium could not account for the hypocalcaemic effect of magnesium. Plasma magnesium concentration during magnesium infusion into cats with an intact thyroid-parathyroid gland complex was slightly, but not significantly higher than in acutely thyroparathyroidectomized cats.

Fabrication of Step-Edge Vertical-Channel Organic Transistors by Selective Electro-Spray Deposition

2015 ◽  
Vol E98.C (2) ◽  
pp. 80-85
Author(s):  
Hiroshi YAMAUCHI ◽  
Shigekazu KUNIYOSHI ◽  
Masatoshi SAKAI ◽  
Kazuhiro KUDO
Keyword(s):  
Spray Deposition ◽  
Vertical Channel ◽  
Step Edge ◽  
Organic Transistors

ECOLOGICAL AND PHYSIOLOGICAL ASSESSMENT OF CHEMICAL COMPOSITION OF DRINKING TAP WATER IN KHANTY-MANSIYSK AND SALEKHARD

2020 ◽  
pp. 159-167
Author(s):  
V.V. Lapenko ◽  
L.N. Bikbulatova ◽  
E.M. Ternikova
Keyword(s):  
Drinking Water ◽  
Chemical Composition ◽  
Water Samples ◽  
Tap Water ◽  
Iron Concentration ◽  
Absorption Spectrometry ◽  
Northern Region ◽  
Transport Processes ◽  
Magnesium Concentration ◽  
Geochemical Environment

Water is very important for humans, as it is a solvent for metabolic products. Moreover, it is necessary for metabolism, biochemical and transport processes. The elemental status in persons depends on the geochemical environment and consumption of bioelements with food and water. The aim of the paper is to conduct a comprehensive assessment of chemical composition of drinking tap water in Khanty-Mansiysk and Salekhard. Materials and Methods. The chemical composition of 100 samples of drinking tap water was analyzed by atomic absorption spectrometry, spectrophotometry and capillary electrophoresis. All in all, there were 50 samples from Khanty-Mansiysk and 50 samples from Salekhard. The results were compared with Sanitary Rules and Norms 2.1.4.1074-01. Results. Drinking tap water in Salekhard contains a significantly higher concentration of iron, which is much above the maximum allowable concentration, if compared to water samples in Khanty-Mansiysk (p=0.03). In the cities under consideration, the water undergoes high-quality reagent-free treatment. However, the deterioration of the water supply networks in Salekhard is 3 times as high as in Khanty-Mansiysk. Calcium and magnesium concentration in water samples from Khanty-Mansiysk is 5.6 and 3.9 times lower than the MAC; in water samples from Salekhard calcium concentration is 6.3 (p=0.008) and magnesium concentration 4.6 (p<0.001) times lower than the MAC. Conclusion. The consumption of ultra-fresh drinking water leads to low intake of bioelements, which are a part of enzymes contributing to the human antioxidant defense and can result in manifestation of cardiovascular diseases. This is especially true for Salekhard with very soft drinking water and high iron concentration, which excess can exhibit prooxidant properties. Keywords: tap water, bioelements, northern region, antioxidants. Вода является важнейшим соединением для человека: необходима в качестве растворителя продуктов метаболизма и протекания обменных, биохимических и транспортных процессов. Элементный статус организма человека зависит от геохимического окружения и поступления биоэлементов с пищей и водой. Цель. Провести комплексную оценку химического состава водопроводной воды городов Ханты-Мансийск и Салехард. Материалы и методы. Методами атомно-абсорбционной спектрометрии, спектрофотометрии и капиллярного электрофореза проанализирован химический состав 100 проб водопроводной воды: по 50 из Ханты-Мансийска и Салехарда. Результаты сравнивали с СанПиН 2.1.4.1074-01. Результаты. В водопроводной воде Салехарда установлена превышающая ПДК и достоверно более высокая концентрация железа сравнительно с водой Ханты-Мансийска (р=0,03). При условии качественной безреагентной водоподготовки в изучаемых городах это обусловлено изношенностью водопроводных сетей в Салехарде, более чем в 3 раза превышающей этот показатель в Ханты-Мансийске. Концентрация кальция и магния в воде Ханты-Мансийска в 5,6 и 3,9 раза ниже ПДК; в воде Салехарда – в 6,3 (р=0,008) и 4,6 (р<0,001) раза ниже ПДК соответственно. Заключение. Употребление ультрапресной питьевой воды на фоне очень малого поступления с водой биоэлементов, входящих в состав ферментов антиоксидантной защиты организма человека, может привести к манифестации кардиоваскулярных заболеваний. Это особенно актуально для г. Салехарда с очень мягкой питьевой водой с повышенным содержанием железа, избыток которого может проявлять прооксидантные свойства. Ключевые слова: водопроводная вода, биоэлементы, северный регион, антиоксиданты.

Microneedle-Assisted Percutaneous Transport of Magnesium Sulfate

2020 ◽  
Vol 17 (2) ◽  
pp. 140-147
Author(s):  
Karna B. Ghimirey ◽  
Kevin Ita
Keyword(s):  
Confocal Microscopy ◽  
Stratum Corneum ◽  
Magnesium Sulfate ◽  
Inductively Coupled Plasma ◽  
Optical Emission ◽  
Magnesium Concentration ◽  
Porcine Skin ◽  
Time Curve ◽  
Student’S T

Objective: In vitro diffusion experiments were performed to assess the permeation of magnesium sulfate across pig skin. Method: The mean thickness of the dermatomed porcine skin was 648 ± 12 µm. Magnesium concentration was measured using inductively coupled plasma-optical emission spectroscopy. Transdermal flux of magnesium sulfate across MN-treated and untreated porcine skin was obtained from the slope of the steady-state linear portion of cumulative amount versus time curve. Results: Statistical analysis of the results was done with Student’s t-test. The transdermal flux of magnesium sulfate across microneedle-treated porcine skin was 134.19 ± 2.4 µg/cm2/h and transdermal flux across untreated porcine skin was 4.64 ± 0.05 µg/cm2/h. Confocal microscopy was used to visualize the microchannels created by a solid microneedle roller (500 µm). Conclusion: From our confocal microscopy studies, it was evident that the 500 μm long microneedles disrupted the stratum corneum and created microchannels measuring 191 ± 37 µm. The increase in transdermal flux across the microneedle-treated skin was statistically significant compared to that of controls, i.e., without the application of microneedles. With the application of microneedles, the transdermal flux of magnesium permeated over 12 h was approximately 33-fold higher in comparison to passive diffusion across an intact stratum corneum.

Association Between Magnesium and Oxidative Stress in Patients with Obesity

2020 ◽  
Vol 16 (5) ◽  
pp. 743-748
Author(s):  
Ana R.S. de Oliveira ◽  
Kyria J.C. Cruz ◽  
Jennifer B.S. Morais ◽  
Juliana S. Severo ◽  
Jéssica B. Beserra ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Thiobarbituric Acid ◽  
Magnesium Concentration ◽  
Control Group ◽  
Compensatory Mechanism ◽  
Thiobarbituric Acid Reactive Substances ◽  
Magnesium Intake ◽  
Significant Difference ◽  
Dietary Magnesium ◽  
And Control

Background: The role of minerals in preventing the generation of oxidative stress in obese individuals has been evaluated. Magnesium is an antioxidant nutrient and a cofactor of enzymes involved in the cell membrane stabilization, attenuating the effects of oxidative stress. Objective: To evaluate the association between magnesium and concentrations of thiobarbituric acid reactive substances (TBARS) in patients with obesity and eutrophic women. Methods: A cross-sectional study was conducted with 73 women, divided into two groups: case group (patients with obesity, n=27) and control group (eutrophic women, n=46). Measurements of body mass index and waist circumference were performed. Dietary magnesium intake was assessed by the three-day food record using the NutWin software. Urinary magnesium concentration was measured by atomic absorption spectrophotometry method. Plasma concentrations of thiobarbituric acid reactive substances (TBARS) were also determined. Results: Mean values of dietary magnesium intake were 161.59 ± 60.04 and 158.73 ± 31.96 for patients with obesity and control group, respectively, with no significant difference between the groups studied (p >0.05). The value of urinary excretion of magnesium was lower than the reference values in both groups, with no significant difference between the groups studied (p >0.05). The plasma concentration of thiobarbituric acid reactive substances was significantly higher in patients with obesity compared to the control group (p <0.001). There was no correlation between levels of magnesium biomarkers and the concentration of TBARS (p >0.05). Conclusion: Patients with obesity showed a reduced dietary magnesium intake which seems to induce hypomagnesuria as a compensatory mechanism. The marker of oxidative stress evaluated in this study was not influenced by magnesium.

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