Determination Of Layer Thickness Research Articles

An inverse method for estimating thickness and volume with time of a thin CO2‐filled layer at the Sleipner Field, North Sea

AbstractMigration of CO2 through storage reservoirs can be monitored using time lapse seismic reflection surveys. At the Sleipner Field, injected CO2 is distributed throughout nine layers within the reservoir. These layers are too thin to be seismically resolvable by direct measurement of the separation between reflections from the top and bottom of each layer. Here we develop and apply an inverse method for measuring thickness changes of the shallowest layer. Our approach combines differences in traveltime down to a specific reflection together with amplitude measurements to determine layer thicknesses from time lapse surveys. A series of synthetic forward models were used to test the robustness of our inverse approach and to quantify uncertainties. In the absence of ambient noise, this approach can unambiguously resolve layer thickness. If a realistic ambient noise distribution is included, layer thicknesses of 1–6 m are accurately retrieved with an uncertainty of ±0.5 m. We used this approach to generate a thickness map of the shallowest layer. The fidelity of this result was tested using measurements of layer thickness determined from the 2010 broadband seismic survey. The calculated volume of CO2 within the shallowest layer increases at a rate that is quadratic in time, despite an approximately constant injection rate into the base of the reservoir. This result is consistent with a diminished growth rate of the areal extent of underlying layers. Finally, the relationship between caprock topography and layer thickness is explored and potential migration pathways that charge this layer are identified.

Parameterized complex dielectric functions of CuIn1−xGaxSe2: applications in optical characterization of compositional non‐uniformities and depth profiles in materials and solar cells

AbstractIn‐situ spectroscopic ellipsometry (SE) was employed to extract the complex dielectric functions ε = ε1 + iε2 over the spectral range of 0.75–6.5 eV for a set of polycrystalline CuIn1−xGaxSe2 (CIGS) thin films with different alloy compositions x = [Ga]/{[In] + [Ga]}. For highest possible accuracy in ε for each CIGS thin film, specialized SE procedures were adopted including (i) deposition to a thickness of ~600 Å on smooth native oxide covered crystal silicon wafers, which minimizes the surface roughness on the film and thus the required corrections in data analysis, and (ii) measurement in‐situ, which minimizes ambient contamination and oxidation of the film surface. Assuming an analytical form for each of the ε spectra for these CIGS films, oscillator parameters were obtained in best fits, and these parameters were fit in turn to polynomials in x. With the resulting database of polynomial coefficients, the ε spectra for any composition of CIGS can be generated from the single parameter, x. In addition to enabling accurate contactless determination of bulk and surface roughness layer thicknesses of CIGS films by high speed multichannel SE, the database enables characterization of the composition and its profile with depth into these films, and even how the depth profile varies spatially within the plane of the films. In this study, depth profile parameters were found to correlate spatially with solar cell performance parameters. As a result, SE provides the capability of contactless compositional analysis of production‐scale CIGS photovoltaic modules at high speed. Copyright © 2016 John Wiley & Sons, Ltd.

Formation of SixNy(H) and C:N:H layers by Plasma-Assisted Chemical Vapor Deposition method

This work includes the results of growth rate of the silicon nitride layers and layers of carbon doped nitrogen deposition on (001) Si substrate as a function of time in the process of chemical vapor deposition, assisted with the plasma generated by radio frequency waves RF CVD (13,56MHz, 300W). On the basis of measurements of thickness of the layers it was observed that kinetic curves are not linear but consist of stages, which regularly recur and are characterized at first by the rapid growth rate and then by slowing down at the end of each stage. The spectroscopic ellipsometry investigations allowed us to determine layer thickness and optical constants parameters, versus deposition time.The obtained results allow us to conclude that the growth process within this system is limited by the number of active centers on the substrate surface, and at the next stages, on the surface of growing layers. A possible mechanism based on the theory on of transition state has been discussed.

Joint Raman spectroscopy and HRXRD investigation of cubic gallium nitride layers grown on 3C-SiC

Cubic gallium nitride (GaN) films are analyzed with highresolution X-ray diffraction (HRXRD) and Raman spectroscopy. Several cubic GaN layers were grown on 3C-SiC (001) substrate by radio-frequency plasma-assisted molecular beam epitaxy. The layer thickness of the cubic GaN was varied between 75 and 505 nm. The HRXRD analysis reveals a reduction of the full-width at half-maximum (FWHM) of omega scans for growing layer thicknesses, which is caused by a partial compensation of defects. The Raman characterization confirms well-formed c-GaN layers. A more detailed examination of the longitudinal optical mode hints at a correlation of the FWHM of the Raman mode with the dislocation density, which shows the possibility to determine dislocation densities by Ramanspectroscopy on a micrometer scale, which is not possible by HRXRD. Furthermore, this Raman analysis shows that normalized Raman spectra present an alternative way to determine layer thicknesses of thin GaN films.

Feasibility of Using 4th Power Law in Design of Plastic Deformation Resistant Low Volume Roads

A low volume road (LVR) structural design has two phases: first one is selection of appropriate construction materials and second is the determination of layer thicknesses under the certain traffic and environmental conditions with considering the subgrade bearing capacity. Pavements are prompted to serve the traffic without reaching the terminal serviceability index over its design life. Rut accumulation (plastic deformation) is the most common pavement deterioration type of flexible pavements. Therefore the main goal of the design is prevent rutting. Many low volume road design manual assume that plastic deformation occurs only in subgrade. Construction of overlying layers by selective high performance materials according to the related material and construction specifications is the reason of this assumption. In fact, the assumption is not much reasonable especially for with no, or thinly overlaid low volume road pavements, where the major structural strength is comprised of unbound granular pavement materials and where the principal distress mechanism is rutting in the aggregate layers.Subgrade bearing capacity and the traffic are the main input parameters in the design stage of low volume roads. Subgrade bearing capacity is expressed with California Bearing Ratio (CBR) or Resilient Modulus (Mr). The “traffic” term is determined by Equivalent Standard Axle Load (ESAL) repetitions which is often admitted as 80kN single axle load. Although it is not too difficult to determine an axle load for an individual vehicle, it becomes quite complicated to determine the number and types of axle loads that a particular pavement will be subjected over its design life. For calculation of Load Damage Factors of different vehicle types, which have various axle load and configurations, a generalized fourth-power law has been used for more than a half century. The objective of this study is to indicate the limitations and difficulties faced on reliably applying a power law relationship in design of LVRs with no, or only thin seals. If a power law relationship to be used due to its simplicity, several parameters must be considered in selection of the power value. Such as stress dependent behavior of unbound granular materials and the selected distress type.

Determination of the Thickness of a Resistive Material Layer in a Finite Volume Conductor using Focused Impedance Method (FIM) – a simulation study

Focused Impedance Method (FIM) is an innovative and relatively new electrical impedance measurement technique that allows localized measurement of the properties of electrically conducting materials in a volume conductor such as the human body using simple measurement setups. In a previous work, FIM, with dual electrode separation, was used to determine thicknesses of subcutaneous fat layers through experimental study on phantoms and human subjects. The present work, carried out using COMSOL Multiphysics software package, is a finite element simulation study for a similar target object that verifies and extends the results of the previous experimental work. A rectangular box of different heights containing a material of uniform conductivity such as saline together with internally embedded layers of resistive materials of different thicknesses were used for this study. The measured transfer impedance in the FIM method showed marked change with the variation of the thickness of the resistive layer and with electrode separation, showing a point of maximum curvature in the latter. We obtained a calibration curve for the thickness from the electrode separation of this point. This allowed a unique method for the determination of thickness of embedded resistive layers which is more general than what had been done in the previous experimental work. This work will help standardize the application of 4-electrode FIM for determination of the thickness of less-conducting material layer in any finite volume, including determination of fat layer thickness, etc.Bangladesh Journal of Medical Physics Vol.7 No.1 2014 8-23

In-Plane Anisotropy in Mono- and Few-Layer ReS2 Probed by Raman Spectroscopy and Scanning Transmission Electron Microscopy.

Rhenium disulfide (ReS2) is a semiconducting layered transition metal dichalcogenide that exhibits a stable distorted 1T phase. The reduced symmetry of this system leads to in-plane anisotropy in various material properties. Here, we demonstrate the strong anisotropy in the Raman scattering response for linearly polarized excitation. Polarized Raman scattering is shown to permit a determination of the crystallographic orientation of ReS2 through comparison with direct structural analysis by scanning transmission electron microscopy (STEM). Analysis of the frequency difference of appropriate Raman modes is also shown to provide a means of precisely determining layer thickness up to four layers.

Optical Properties of Titania Coatings Prepared by Inkjet Direct Patterning of a Reverse Micelles Sol-Gel Composition.

Thin layers of titanium dioxide were fabricated by direct inkjet patterning of a reverse micelles sol-gel composition onto soda-lime glass plates. Several series of variable thickness samples were produced by repeated overprinting and these were further calcined at different temperatures. The resulting layers were inspected by optical and scanning electronic microscopy and their optical properties were investigated by spectroscopic ellipsometry in the range of 200–1000 nm. Thus the influence of the calcination temperature on material as well as optical properties of the patterned micellar titania was studied. The additive nature of the deposition process was demonstrated by a linear dependence of total thickness on the number of printed layers without being significantly affected by the calcination temperature. The micellar imprints structure of the titania layer resulted into significant deviation of measured optical constants from the values reported for bulk titania. The introduction of a void layer into the ellipsometric model was found necessary for this particular type of titania and enabled correct ellipsometric determination of layer thickness, well matching the thickness values from mechanical profilometry.

Low frequency acoustic pulse propagation in temperate forests.

Measurements of acoustic pulse propagation for a 30-m path were conducted in an open field and in seven different forest stands in the northeastern United States consisting of deciduous, evergreen, or mixed tree species. The waveforms recorded in forest generally show the pulse elongation characteristic of propagation over a highly porous ground surface, with high frequency scattered arrivals superimposed on the basic waveform shape. Waveform analysis conducted to determine ground properties resulted in acoustically determined layer thicknesses of 4-8 cm in summer, within 2 cm of the directly measured thickness of the litter layers. In winter the acoustic thicknesses correlated with the site-specific snow cover depths. Effective flow resistivity values of 50-88 kN s m(-4) were derived for the forest sites in summer, while lower values typical for snow were found in winter. Reverberation times (T60) were typically around 2 s, but two stands (deciduous and pruned spruce planted on a square grid) had lower values of about 1.2 s. One site with a very rough ground surface had very low summer flow resistivity value and also had the longest reverberation time of about 3 s. These measurements can provide parameters useful for theoretical predictions of acoustic propagation within forests.

Modified Structural Number Determined from Falling Weight Deflectometer Deflection Bowl Parameters and Its Proposed Use in a Benchmark Methodology

The structural capacities of various flexible pavements are often determined with the SNC (modified structural number) or SNP (adjusted structural number). The need for a non-destructive measurement technique, such as the FWD (falling weight deflectometer), had previously been explored to overcome the laborious test pit material characterization and layer thickness determination which had normally been needed to determine SNC or SNP. Lately, viable correlations were established between SNP/SNC and a variety of FWD deflection bowl measuring points or parameters. However, a large portion of the inherent structural information in the rest of the deflection bowl remains unused. The paper presents and validates relationship between effective structural number (SNeff for pavement layers contribution) and for adjusted structural number (SNPeff) and deflection bowl parameters utilizing the whole deflection bowl. The latter is inclusive of subgrade contribution. SNP is widely used to gather information on the structural integrity of the pavement system during preliminary network or project level investigations. A range of SNPeff values are suggested for preliminary investigations using a benchmark methodology to help guide more efficient detailed investigations. However, using SNPeff in this benchmark fashion cannot identify origin of the distress in a pavement system. The complementary use of deflection bowl parameter benchmark analysis can greatly enhance such investigations based on SNPeff and identify origin of distress. In this paper, the use of SNPeff, complemented with deflection bowl parameter benchmark analysis, is demonstrated with a case study.

Investigation of the Adsorption Mechanism of Heterocyclic Molecules on Copper using Potentiodynamic ORP-EIS and In-situ Ramans pectroscopy

The adsorption mechanism of 2-amino-5-mercapto-1,3,4-thiadiazole (AMTD) and 2-methyl-5-mercapto-1,3,4-thiadiazole (MMTD) was investigated by a combined electrochemical and surface analysis approach. The link with the adsorption kinetics was maintained during AC voltammetry as well as during potentiodynamic broadband multisine (ORP-EIS) measurements. A discrepancy between the thickness of the adsorbate layers determined by both techniques was identified as a result of the frequency dispersion of the system. The use of a broad frequency range and the statistical evaluation with ORP-EIS deemed this the preferential technique for layer thickness determination. The surface-molecular complex was further investigated through in-situ surface enhanced Raman spectroscopy (SERS), collected under identical electrochemical conditions. The adsorption regions defined by the AC voltammetry measurements corresponded to the SERS response. The proposed adsorption orientation for AMTD and MMTD was through N4-S-Cu σ-bonding. A layer thickness of 0.76 nm and 0.85 nm respectively indicated the formation of multiple adsorbed molecular layers. Application of the in-situ approach on small heterocyclic molecules derived from AMTD and MMTD indicated the importance of adjacent nitrogen atoms in a five membered heterocyclic ring for the adsorbate-substrate complex.

Investigation of coating layer morphology by micro-computed X-ray tomography

Spray fluidized bed coating is a common process in food, chemical and pharmaceutical industry. Morphology of the formed layer is essential for product quality. Therefore, layer morphology was investigated in detail by X-ray micro-computed tomography (μ-CT) for porous γ-alumina particles coated with a solution of sodium benzoate with some hydroxypropyl-methylcellulose in water. Investigated properties are: layer thickness distribution on individual particles, porosity of the layer, and average layer thickness. The determination of layer thickness was performed in two different ways: (1) using two-dimensional cross-sections of volume images obtained from full μ-CT measurements, and (2) using single X-ray irradiation images without sample rotation. The porosity of the coating layer was evaluated from the volume images. Further studies were performed to investigate the influence of operating parameter, e.g. exposure time, on image quality and the obtained results. Special attention was put on ways to reduce the necessary measurement time while preserving the quality of the results. Finally, a new measurement protocol is presented which allows to measure coating thickness distributions in a particle population.

Optical coherence tomography accurately identifies patients with penile (pre) malignant lesions: A single center prospective study.

Introduction:Currently, (multiple) biopsies are taken to obtain histopathological diagnosis of suspicious lesions of the penile skin. Optical coherence tomography (OCT) provides noninvasive in vivo images from which epidermal layer thickness and attenuation coefficient (μoct) can be quantified. We hypothesize that qualitative (image assessment) and quantitative (epidermal layer thickness and attenuation coefficient, μoct) analysis of penile skin with OCT is possible and may differentiate benign penile tissue from (pre) malignant penile tissue.Materials and Methods:Optical coherence tomography-imaging was performed prior to punch biopsy in 18 consecutive patients with a suspicious lesion at the outpatient clinic of the NKI-AVL. Qualitative analysis consisted of visual assessment of clear layers and a visible lower border of the lesions, quantitative analysis comprised of determination of the epidermal layer thickness and μoct. Results were grouped according to histopathology reports.Results:Qualitative analysis showed a statistically significant difference (P = 0.047) between benign and (pre) malignant lesions. Quantitative analysis showed that epidermal layer thickness and attenuation coefficient was significantly different between benign and (pre) malignant tissue, respectively, P = 0.001 and P < 0.001.Conclusion:In this preliminary study, qualitative and quantitative analysis of OCT-images of suspicious penile lesions shows differences between benign lesions and (pre) malignant lesions. These results encourage further research in a larger study population.

Material Characterization of Layered Structures with Ultrasound

This contribution presents a method for the simultaneous determination of sound velocity and thickness of a system consisting of two layers. To obtain additional information, beside the time of flight (TOF), the amplitude is evaluated. The amplitude of a reflected sound wave depends on the position of the interface in the sound field of the probe and is maximal, if the focus lies on the interface. The focus position is varied by the use of an annular array and the amplitude as a function of the adjusted focus position is evaluated. Since the sound field of the ring elements of the annular array has distinctly side lobes, transverse waves are excited in the specimen and the sound velocity of the transversal wave can also be determined.The method is demonstrated for the determination of layer thicknesses and sound velocities (longitudinal and transversal) on a two layered system.

Characterization of hollow fiber membranes by impedance spectroscopy

Electrical impedance spectroscopy (EIS) is a simple and non-destructive method to characterize membranes and to monitor membrane processes. It can be used for instance to determine layer thicknesses or to observe fouling. Up to now it has only been applied to flat sheet membranes using a four-electrode measuring technique. Hollow fiber membranes are finding increasing application but monitoring the state of such membranes during operation is a difficult task. The aim of our work presented here is to adapt the electrical impedance spectroscopy method for use with hollow fiber membranes.For this purpose a new membrane module has been developed which allows electrical impedance measurements to be made on hollow fibers and capillary membranes using a 2-terminal method. For this one wire-shaped electrode is located inside the hollow fiber membrane and one ring-shaped electrode is located outside, around the membrane. In the experiments the applied AC field used in the impedance measurements was in a radial direction; across the membrane from the lumen side to the shell side while the system was bathed by an electrolyte solution. A porous hydrophobic PP membrane with a pore size of 0.2µm has been intensively analyzed with the new device to explore the characteristics of the new methodology.The impedance of the ionic double layers and the frequency dependence of those impedances, at the two electrodes used in these experiments pose a major problem. These complications can normally be avoided by the use of 4-terminal methods but this is even more intricate to do with the hollow fiber geometry due to lack of space. Nevertheless, using the 2-terminal technique, it was possible to obtain meaningful impedance spectra. The membrane׳s impedance could be determined and a significant influence of the membrane wetting could be observed. Such wetting phenomena are often speculated about when analyzing flux data, but can now be quantified systematically. Furthermore, we present a comprehensive model to illustrate the opportunities and challenges for the developed technique.

The Reduced Cross-Section Method for Evaluation of the Fire Resistance of Timber Members: Discussion and Determination of the Zero-Strength Layer

The reduced cross-section method (RCSM) is included in Eurocode 5 (EN-1995-1-2) for the design of timber members in fire conditions. The method considers the strength and stiffness reduction beneath the charred layer by adding an additional depth (known as the ‘zero-strength’ layer) to the charring depth. The zero-strength layer is one of the key parameters for the fire design of timber members. Recently, some concerns have been raised that the zero-strength layer might be non-conservative in some applications. This paper presents the background to the RCSM, followed by a short discussion on the mechanical assumptions, simplifications and possible limitations of the method itself. Further, it discusses determination of the zero-strength layer thickness for members in bending, tension and compression, and provides guidelines on the use of standard experimental tests to determine this quantity. For demonstration of the determination procedure, the results of fire tests in bending, tension and compression were analysed following the described procedure. Results show that the zero-strength layer exceeds the value used in practice, indicate that the method of Eurocode 5 may be non-conservative and should be revised.

Hydration Layers on Clay Mineral Surfaces in Aqueous Solutions: a Review/Warstwy Uwodnione Na Powierzchni Minerałów Ilastych W Roztworach Wodnych: Przegląd

Abstract Hydration layer on clay mineral surfaces is originated from the adsorption of polar water molecules and hydrated cations on the surfaces through unsaturated ionic bonds, hydrogen bonds and van der Waals bonds. It has attracted great attentions because of their important influences on the dispersive stability of the particles in aqueous solutions. This review highlighted the molecular structure of clay minerals, the origin of hydration layers on clay mineral surfaces, the hydration layer structural model, hydration force and the main parameters of affecting the hydration layers on clay minerals (crystal structure, cationic type and strength, and solution pH). Also, the research methods for hydration layers were briefly described, especially the determination of hydration layer thickness by the Einstein viscosity method and AFM method. In addition, the applications of the stability of fine clay mineral particles in aqueous suspensions were summarized.

Neural Network–Based Thickness Determination Model to Improve Backcalculation of Layer Moduli without Coring

Traditionally, deflection data from a falling weight deflectometer (FWD) test and thickness data from pavement coring are used to backcalculate layer moduli. In this study, instead of coring, a neural network (NN) model is developed to determine layer thickness from FWD time-deflection histories. Using the NN predicted thicknesses, layer moduli are backcalculated using a commercially available backcalculation software. For validation, backcalculated moduli are compared with the laboratory determined moduli. Results show that backcalculated moduli are nearly equal to the laboratory moduli. Thus, the inclusion of NN-based thickness data has the potential to replace pavement coring, which is very expensive, and/or to enable a backcalculation method to run with a reasonable assumption of thickness whenever coring information is not available.

Determination of interface locations and layer thicknesses in SIMS and AES depth profiling of Si/Ti multilayer films by 50 at% definition

Determination of the interface locations and the layer thicknesses in SIMS depth profiling of Si/Ti multilayer films was investigated by cesium ion beam. The raw SIMS depth profiles were converted to the compositional depth profiles by the relative sensitivity factors of Si and Ti derived from the atomic fractions of a reference Si‐Ti alloy film determined by Rutherford backscattering spectroscopy. The locations of the interfaces were determined by 50 at% definition in the compositional SIMS depth profiles, and the thicknesses of the Si and Ti layers were measured from the interfaces. The layer thicknesses of the Si/Ti multilayer film were also investigated by Auger electron spectroscopy depth profiling using the same process and same definition. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Traceable thickness determination of organic nanolayers by X‐ray reflectometry

While several methods are available for layer thickness determination in the nanometer range, very few of them are suited for absolute measurements that can be traced to the SI units. Layer thickness determination from the oscillations that are observed in X‐ray reflectometry for metallic layers or oxides is well established, but the low density of most organic materials results in low contrast and thus weak oscillations. However, by using synchrotron radiation instead of X‐ray tubes, any photon energy can be selected, also in the range below 2 keV, to enhance the contrast significantly. The organic layers systems investigated here are Irganox 1010 and Fmoc‐pentafluoro‐L‐phenylalanine layers with nominal thicknesses between 20 and 100 nm, deposited on silicon wafers with a nominal 20 nm SiO2 layer. The measurements were performed at a photon energy of 1841 eV close to the Si K‐absorption edge. Pronounced oscillations with different periodicities were observed for all investigated systems. After determination of the critical angle, the measured reflectance is divided by the Fresnel reflectance. A Fourier transform of the remaining signal results in the power spectral density. The peaks in the spectra correspond to the thicknesses of individual layers or groups of layers. These organic bilayer systems can be clearly distinguished from monolayers and, with some knowledge on the sample structure, the individual layer thicknesses are obtained with low uncertainties. This enables the development of reference materials with certified thickness of organic layers. Copyright © 2014 John Wiley &amp; Sons, Ltd.