Characterization of the Silicon / Fluoride Solution Interface by In-Situ Microwave Reflectivity

MRS Proceedings ◽

10.1557/proc-451-197 ◽

1996 ◽

Vol 451 ◽

Author(s):

Arun Natarajan ◽

Gerko Oskam ◽

Douglas A. Oursler ◽

Peter C. Searson

Keyword(s):

Electrochemical Impedance ◽

Surface States ◽

Active Surface ◽

Potential Region ◽

Flat Surfaces ◽

Solution Interface ◽

Valence Bands

ABSTRACTEtching of silicon in aqueous fluoride solutions can lead to almost atomically flat surfaces with a low density of surface states and recombination centers. The final quality of the surface, however, is strongly dependent on the solution composition and pH. We have performed electrochemical impedance spectroscopy in combination with potential modulated microwave reflectance spectroscopy (PMMRS) to elucidate the processes occurring at the surface during etching. PMMRS is a novel technique that only probes the free carriers in the conduction and valence bands and is, under certain conditions, not affected by processes involving electrically active surface states or charge transfer. This unique feature allows us to separate the energetics of the semiconductor from surface processes. Microwave reflectivity (δR) versus potential curves in HF solutions demonstrate the variation of the flatband potential as a function of pH. The AR response in the narrow potential region around the flatband potential and at more negative potentials is also discussed.

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Automated Testing and Characterization of Additive Manufacturing (ATCAM)

Journal of Materials Engineering and Performance ◽

10.1007/s11665-021-06042-2 ◽

2021 ◽

Author(s):

Arash Alex Mazhari ◽

Randall Ticknor ◽

Sean Swei ◽

Stanley Krzesniak ◽

Mircea Teodorescu

Keyword(s):

Additive Manufacturing ◽

Fused Deposition Modeling ◽

Cell System ◽

Automated Testing ◽

Fused Deposition ◽

Deposition Modeling ◽

Machine Calibration

AbstractThe sensitivity of additive manufacturing (AM) to the variability of feedstock quality, machine calibration, and accuracy drives the need for frequent characterization of fabricated objects for a robust material process. The constant testing is fiscally and logistically intensive, often requiring coupons that are manufactured and tested in independent facilities. As a step toward integrating testing and characterization into the AM process while reducing cost, we propose the automated testing and characterization of AM (ATCAM). ATCAM is configured for fused deposition modeling (FDM) and introduces the concept of dynamic coupons to generate large quantities of basic AM samples. An in situ actuator is printed on the build surface to deploy coupons through impact, which is sensed by a load cell system utilizing machine learning (ML) to correlate AM data. We test ATCAM’s ability to distinguish the quality of three PLA feedstock at differing price points by generating and comparing 3000 dynamic coupons in 10 repetitions of 100 coupon cycles per material. ATCAM correlated the quality of each feedstock and visualized fatigue of in situ actuators over each testing cycle. Three ML algorithms were then compared, with Gradient Boost regression demonstrating a 71% correlation of dynamic coupons to their parent feedstock and provided confidence for the quality of AM data ATCAM generates.

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Mechanistic Insights into the Spontaneous Reaction Between CO2 and La2-xSrxCuO4

Canadian Journal of Chemistry ◽

10.1139/cjc-2021-0059 ◽

2021 ◽

Author(s):

Alexander William Henry Whittingham ◽

Jordan Lau ◽

Rodney David Lucien Smith

Keyword(s):

Electrochemical Impedance ◽

Co2 Reduction ◽

Active Surface ◽

Structural Instability ◽

Redox Couple ◽

Surface Sites ◽

Carbonate Ions ◽

Redox Active ◽

Spontaneous Reaction

Layered perovskites such as La2-xSrxCuO4 are active electrocatalysts for CO2 reduction, but they suffer from structural instability under catalytic conditions. This structural instability is found to arise from the reaction of CO2 with surface sites. Variable scan rate voltammetry shows the growth of a Cu-based redox couple when potentials cathodic of 0.6 V vs. RHE are applied in the presence of CO2. Electrochemical impedance spectroscopy identifies a redox active surface state at this voltage, whose concentration is increased by electrochemical reduction in the presence of CO2. In-situ spectroelectrochemical FTIR identifies surface bound carbonates as being involved formation of these surface sites. The orthorhombic lattice for La2-xSrxCuO4 is found to uniquely enable monodentate binding of (bi)carbonate ions from solution as well as bidentate carbonate ions through reaction with CO2. The incorporation of Sr(II) induces a transition to a tetragonal lattice, for which only monodentate carbonate ions are observed. It is proposed that the binding of carbonate ions in a bidentate fashion generates sufficient strain at the surface to result in amorphization at the surface, yielding the observed Cu(II)/Cu(I) redox couple.

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Quantitative Single-Cell Transcript Assessment of Biomarkers Supports Cellular Heterogeneity in the Bovine IVD

Veterinary Sciences ◽

10.3390/vetsci6020042 ◽

2019 ◽

Vol 6 (2) ◽

pp. 42 ◽

Cited By ~ 1

Author(s):

Kangning Li ◽

Devin Kapper ◽

Sumona Mondal ◽

Thomas Lufkin ◽

Petra Kraus

Keyword(s):

In Situ Hybridization ◽

Single Cell ◽

Gaussian Mixture ◽

Cellular Heterogeneity ◽

Rna In Situ Hybridization ◽

Ivd Degeneration

Severe and chronic low back pain is often associated with intervertebral disc (IVD) degeneration. While imposing a considerable socio-economic burden worldwide, IVD degeneration is also severely impacting on the quality of life of affected individuals. Cell-based regenerative medicine approaches have moved into clinical trials, yet IVD cell identities in the mature disc remain to be fully elucidated and tissue heterogeneity exists, requiring a better characterization of IVD cells. The bovine coccygeal IVD is an accepted research model to study IVD mechano-biology and disc homeostasis. Recently, we identified novel IVD biomarkers in the outer annulus fibrosus (AF) and nucleus pulposus (NP) of the mature bovine coccygeal IVD through RNA in situ hybridization (AP-RISH) and z-proportion test. Here we follow up on Lam1, Thy1, Gli1, Gli3, Noto, Ptprc, Scx, Sox2 and Zscan10 with fluorescent RNA in situ hybridization (FL-RISH) and confocal microscopy. This permits sub-cellular transcript localization and the addition of quantitative single-cell derived values of mRNA expression levels to our previous analysis. Lastly, we used a Gaussian mixture modeling approach for the exploratory analysis of IVD cells. This work complements our earlier cell population proportion-based study, confirms the previously proposed biomarkers and indicates even further heterogeneity of cells in the outer AF and NP of a mature IVD.

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Growth and Characterization of Single Crystal Epitaxial CoGa on MBE Grown III-V Semiconductors

MRS Proceedings ◽

10.1557/proc-144-613 ◽

1988 ◽

Vol 144 ◽

Author(s):

K. C. Garrison ◽

C. J. Palmstrøm ◽

R. A. Bartynski

Keyword(s):

Substrate Temperature ◽

Single Crystal ◽

Single Crystals ◽

Structural Quality ◽

High Quality ◽

Auger Analysis ◽

Post Deposition

ABSTRACTWe have demonstrated growth of high quality single crystal CoGa films on Ga1−xAlxAs. These films were fabricated in-situ by codeposition of Co and Ga on MBE grown Ga1−xAlxAs(100) surfaces. The elemental composition of the films was determined using Rutherford Backscattering (RBS) and in-situ Auger analysis. The structural quality of the films' surfaces was studied using RHEED (during deposition) and LEED (post deposition). RBS channeling was used to determine the bulk crystalline quality of these films.For ∼500 Å CoGa films grown at ∼450°C substrate temperature, channeling data showed good quality epitaxial single crystals [χmin ∼7%] with minimal dechanneling at the interface.

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Quality indices of groundwater for agricultural use in the Soconusco, Chiapas, Mexico

Earth Sciences Research Journal ◽

10.15446/esrj.v21n3.63455 ◽

2017 ◽

Vol 21 (3) ◽

pp. 117-127 ◽

Cited By ~ 4

Author(s):

Germán Santacruz de León ◽

JOSE ALFREDO RAMOS LEAL ◽

JANETE MORAN RAMIREZ ◽

BRISEIDA LOPEZ ALVAREZ ◽

EUGENIO ELISEO SANTACRUZ DE LEON

Keyword(s):

Water Medium ◽

Quality Indices ◽

Sodium Percentage ◽

Agricultural Use ◽

Magnesium Adsorption Ratio ◽

Anomalous Point ◽

Very High

In Soconusco, Chiapas, in spite of the high availability of surface water, it is resorting to the use of groundwater. Knowledge about the quality of surface or groundwater used to irrigate crops in that region is low. This paper aims to contribute to the knowledge of the quality of groundwater for agricultural use through the characterization of the spatial variability. Assuming a random spatial distribution of 45 samples which were collected in situ were determined: acidity and alkalinity (pH), electrical conductivity (EC), Total Dissolved Solids (TDS), cations and anions and trace elements; in addition to the agricultural index: Sodium Adsorption Ratio (SAR), Residual Sodium Carbonate (RSC), Soluble Sodium Percentage (SSP), Sodium Percentage (% Na), Kelly Ratio (KR), Magnesium Adsorption Ratio (MAR), Permeability Index (PI), Effective Salinity (ES), Salinity Potential (SP) and Osmotic Potential (OP). In general, SSP, % Na, KR, PI are low, there is only one anomalous point (9) with high values at W of the study area. Similarly, PS, ES, Cl, Na and SAR are low except point 16 and conversely, RSC and pH are high, except at this point located in the center of the study area. The results allow us to infer that the water in that aquifer presents no problems or sodicity toxic ions. In 27 sites sampled values above 250 µmhos/cm were found at 25°C, classified as medium to high risk of salinity, unsuitable for agricultural use. Analysis of the combined effect of the presence of sodium (SAR) and salinity (EC or TDS) shows that 27 of analyzing sites have restricted water medium at very high for use in irrigation.

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Characterization of fouling and concentration polarization in ion exchange membrane by in-situ electrochemical impedance spectroscopy

Journal of Membrane Science ◽

10.1016/j.memsci.2019.117443 ◽

2020 ◽

Vol 594 ◽

pp. 117443 ◽

Cited By ~ 5

Author(s):

Lingling Zhang ◽

Hui Jia ◽

Jie Wang ◽

Haitao Wen ◽

Juan Li

Keyword(s):

Electrochemical Impedance Spectroscopy ◽

Impedance Spectroscopy ◽

Ion Exchange ◽

Concentration Polarization ◽

Electrochemical Impedance ◽

Ion Exchange Membrane ◽

Exchange Membrane

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In-Situ Characterization Of Ultra-Small Magnetic Junctions Made By Electrochemical Techniques

MRS Proceedings ◽

10.1557/proc-674-t5.9 ◽

2001 ◽

Vol 674 ◽

Cited By ~ 3

Author(s):

A. Sokolov ◽

J.R. Jennings ◽

C-S Yang ◽

J. Redepenning ◽

B. Doudin

Keyword(s):

Electrochemical Impedance Spectroscopy ◽

Impedance Spectroscopy ◽

Low Temperatures ◽

Coulomb Blockade ◽

Electrochemical Impedance ◽

Electrochemical Techniques ◽

In Situ Characterization

ABSTRACTElectrochemical impedance spectroscopy is used to characterize the growth of NiO over Ni electrodes. We find a limited increase of thickness and a significant increase of porosity of the oxide as a function of time and anodization potential. Conductance measurements performed on Ni/NiO/Co junctions of 30 nm diameters indicate the presence of a Coulomb blockade at low temperatures and small bias. Tunneling is observed at higher bias. Small magnetoresistance ratios (1%) are found.

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