Simultaneous Determination Of Thickness Research Articles

Simultaneous determination of thickness and refractive index using Cauchy or Sellmeier formulas by the example of surface plasmon resonance study on ultrathin polysulfone film

A three-wavelength method based on Cauchy or Sellmeier formulas is proposed for simultaneous determination of the thickness and refractive index without using approximate expansions of the refraction index over the wavelength. The method is also applicable for the simultaneous determination of other optical characteristics together with the refractive index. To test the applicability of the proposed method, the refractive index and thickness of ultrathin polysulfone film were obtained in the surface plasmon resonance experiment.

Simultaneous determination of the thickness and refractive index dispersion of dielectric films by the Paul wavelet transform

The continuous wavelet transform with Paul wavelet was proposed as a method for the simultaneous determination of physical thickness and refractive index dispersion of dielectric films in the visible and near infrared region. Transmittance spectrums, acquired at two different incident angles, were used for the calculations. By this way refractive index dispersion was obtained without knowing the film thickness. The method was tested with simulated data and experimentally applied to a sample of borosilicate glass. The obtained thickness and refractive index dispersion values were compared to the values obtained by the envelope method and the ones provided by the manufacturer.

Probing the thickness and roughness of the functional layer in thin film composite membranes

The thickness and roughness of the functional layer in thin film composite membranes (TFCMs) are important determinants of the membrane performance, whether in reverse osmosis, gas separation or energy applications. This paper describes and compares different techniques for the measurement of these quantities. A new method based on atomic force microscopy (AFM) is developed and compared with techniques based on scanning electron microscopy (FEG-SEM) and profilometry. AFM and profilometry methods allowed a simultaneous determination of thickness and roughness and could be extended for studying the effect of parameters such as support membrane roughness. The methods have been tested on polyamide TFC RO membranes. The membranes were prepared by an interfacial polycondensation technique on polysulfone support, by reaction between m-phenylene diamine and trimesoyl chloride in the organic phase. Based on our earlier work which showed the important role of shear on membrane morphology in such syntheses, preparations both with and without shear were employed. The measurement of thickness using AFM was carried out on specially made membranes in which, by the use of a mask, only a part of the PSF was coated with the PA layer. By scanning a region that contains both the covered and the uncovered parts, thickness values could be obtained. In the second technique, the SEM cross sectional images of TFCMs allowed the determination of the distribution of thickness over the area seleted. In the third, a surface profilometer was used to determine the thickness of de-laminated PA films. The thickness distributions and average thicknesses measured from all three methods matched closely. Overall, these techniques are of great potential in TFC and similar membrane characterization.

Simultaneous determination of thickness, thermal conductivity and porosity in textile material design

Abstract The thickness, thermal conductivity and porosity of textile material are three key factors which determine the heat-moisture comfort level of the human body to a large extent based on the heat and moisture transfer process in the human body-clothing-environment system. This paper puts forward an Inverse Problem of Textile Thickness-Heat conductivity-Porosity Determination (IPT(THP)D) based on the steady-state model of heat and moisture transfer and the heat-moisture comfort indexes. Adopting the idea of the weighted least-squares method, we formulate IPT(THP)D into a function minimization problem. We employ the Particle Swarm Optimization (PSO) method to stochastically search the optimal solution of the objective function. We put the optimal solution into the corresponding direct problem to verify the effectiveness of the proposed numerical algorithms and the validity of the IPT(THP)D.

Simultaneous Determination of Thickness and Heat Conductivity in Fabric Design: Steady-state Modeling and PSO Algorithms

Simultaneous Determination of Thickness and Heat Conductivity in Fabric Design: Steady-state Modeling and PSO Algorithms

Simultaneous determination of thickness and refractive index based on time-of-flight measurements of terahertz pulse

We present a simple technique for simultaneous determination of thickness and refractive index of plane-parallel samples in the terahertz radiation domain. The technique uses time-of-flight measurements of the terahertz pulse. It has been employed on nine different polymers and semiconductor materials, which are transparent for terahertz frequencies. Our results of thickness measurement are in good agreement with micrometer reading. The accuracy in the determination of refractive index is on the order of two decimal points.

Real-time terahertz material characterization by numerical three-dimensional optimization

Terahertz time domain spectroscopy allows for characterization of dielectrics even in cases where the samples thickness is unknown. However, a parameter extraction over a broad frequency range with simultaneous thickness determination is time consuming using conventional algorithms due to the large number of optimization steps. In this paper we present a novel method to extract the data. By employing a three dimensional optimization algorithm the calculation effort is significantly reduced while preserving the same accuracy level as conventional approaches. The presented method is even fast enough to be used in imaging applications.

Principles and Methodology for the Simultaneous Determination of Thickness and Dielectric Constant of Coatings With Capacitance Measurements

We propose a new methodology to measure both the dielectric constant and thickness of dielectric coatings on a flat conducting substrate from two capacitance measurements. We discuss the principles of the method and demonstrate its feasibility using 2-D numerical simulations. We present a proof of principles experiment confirming the viability of the method in practice. Finally, we propose and analyze a multisphere electrode geometry

Dual polarization interferometry characterization of carbohydrate–protein interactions

Dual polarization interferometry (DPI) is an analytical technique that allows the simultaneous determination of thickness, density, and mass of a biological layer on a sensing waveguide surface in real time. The technique was applied to the analysis of carbohydrate–protein interactions. The selected system involved a 12-kDa recombinant fragment of collagen V (HepV) and heparin, a complex polysaccharide. Here we report on the analysis of thickness, density, and mass of surface structures obtained during the binding of HepV to heparin, which is a useful model compound for the sulfated, protein-binding regions of heparan sulfate. This system, which was initially studied for its biological relevance, displayed anomalous behavior in kinetic studies using surface plasmon resonance (SPR) assays that has been attributed to putative conformational changes. It was this putative conformational change that prompted us to investigate the binding using an alternative analytical approach. While using DPI to monitor binding events, a streptavidin layer (surface coverage 2.105 ng mm −2) was bound to the sensor surface (92% coverage), which captured 0.105 ng mm −2 of biotinylated heparin (a stoichiometric ratio of 1:6 heparin–streptavidin). The heparin inserted into the streptavidin layer but was still found to be capable of binding 0.154 ng mm −2 of HepV, which was also observed to insert into the streptavidin layer. This allowed the reliable calculation of the stoichiometric ratio for the HepV–heparin complex (∼1.7:1.0), which has proved to be difficult to evaluate by SPR assays. Furthermore, real-time analysis of the heparin–HepV interaction by DPI suggested that there was some surface loss (probably of streptavidin) while the binding was occurring rather than the putative conformational change that has been suggested on the basis of kinetic data alone. This gives further insight into the binding mechanism of HepV to heparin.

The quantitative analysis of thin specimens: a review of progress from the Cliff‐Lorimer to the new ζ‐factor methods

A new quantitative thin-film X-ray analysis procedure termed the zeta-factor method is proposed. This new zeta-factor method overcomes the two major limitations of the conventional Cliff-Lorimer method for quantification: (1) use of pure-element rather than multielement, thin-specimen standards and (2) built-in X-ray absorption correction with simultaneous thickness determination. Combined with a universal, standard, thin specimen, a series of zeta-factors covering a significant fraction of the periodic table can be estimated. This zeta-factor estimation can also provide information about both the detector efficiency and the microscope-detector interface system. Light-element analysis can also be performed more easily because of the built-in absorption correction. Additionally, the new zeta-factor method has several advantages over the Cliff-Lorimer ratio method because information on the specimen thickness at the individual analysis points is produced simultaneously with compositions, thus permitting concurrent determination of the spatial resolution and the analytical sensitivity. In this work, details of the zeta-factor method and how it improves on the Cliff-Lorimer approach are demonstrated, along with several applications.

Dual polarisation interferometry characterisation of DNA immobilisation and hybridisation detection on a silanised support

Dual polarisation interferometry is an analytical technique that allows the simultaneous determination of thickness, density and mass of a biological layer on a sensing waveguide surface in real time. We evaluated, for the first time, the ability of this technique to characterise the covalent immobilisation of single stranded probe DNA and the selective detection of target DNA hybridisation on a silanised support. Two immobilisation strategies have been evaluated: direct attachment of the probe molecule and a more complex chemistry employing a 1,2 homobifunctional crosslinker molecule. With this technique we demonstrate it was possible to determine probe orientation and measure probe coverage at different stages of the immobilisation process in real time and in a single experiment. In addition, by measuring simultaneously changes in thickness and density of the probe layer upon hybridisation of target DNA, it was possible to directly elucidate the impact that probe mobility had on hybridisation efficiency. Direct covalent attachment of an amine modified 19 mer resulted in a thickness change of 0.68 nm that was consistent with multipoint attachment of the probe molecule to the surface. Blocking with BSA formed a dense layer of protein molecules that absorbed between the probe molecules on the surface. The observed hybridisation efficiency to target DNA was approximately 35%. No further significant reorientation of the probe molecule occurred upon hybridisation. The initial thickness of the probe layer upon attachment to the crosslinker molecule was 0.5 nm. Significant reorientation of the probe molecule surface normal occurred upon hybridisation to target DNA. This indicated that the probe molecule had greater mobility to hybridise to target DNA. The observed hybridisation efficiency for target DNA was approximately 85%. The results show that a probe molecule attached to the surface via a crosslinker group is better able to hybridise to target DNA due to its greater mobility.

Colour properties of barrier anodic oxide films on aluminium and titanium studied with total reflectance and spectroscopic ellipsometry

Colour properties of barrier anodic oxide films on Al and Ti are studied. The anodised systems are described using the L* a* b* scale, total reflectance (TR) and spectroscopic ellipsometry (SE). SE is performed in the visual wavelength range and allows simultaneous determination of thickness and refractive index of the anodically formed oxide film. Subsequently SE results predict TR well and prove that the colours are obtained from interference effects. Anodised Ti shows much higher colour saturation than anodised Al. The difference in colour appearance is explained in terms of different reflectance of both metals; it depends less on the difference in refractive index of the oxides.

Simultaneous determination of thickness and optical constants of polymer thin film by analyzing transmittance.

We present a novel method for determining both the thickness and the optical constants of a weakly absorbing thin film upon a nearly transparent substrate through analysis of transmittance measured at various incident angles with coherent light. We demonstrate this method for a polymer thin film. The refractive indices and extinction coefficients of poly(DRI-anthranilic acid) at wavelengths of 1,064, 632.8, and 532 nm were determined for the first time to our knowledge. We also confirmed the validity of our method with a polystyrene thin film whose optical constant was known. It was found that a thickness of a few hundred nanometers can easily be measured and that this method offers simplicity as well as the capability of in situ measurement.

In-situ thin film diagnostics using waveguide mode spectroscopy

A new method for in-situ film characterisation during thin film deposition processes was developed using waveguide mode spectroscopy. The advantages of the method are a high sensitivity for thin films in the nm-regime and a relatively simple and low-cost set-up. The detection method relies on a double grating coupler allowing a background-free detection of the propagation constants of guided optical modes. The set-up is based on a reflected mode m-line geometry requiring no moving parts. The method was applied to thin film diagnostics in plasma-assisted deposition processes and allowed for the simultaneous determination of thickness and refractive index of the plasma polymer film during deposition. The in-situ waveguide mode spectrometer was also used to monitor gas phase reactions of plasma polymerised maleic anhydride thin films on-line.

Analysis of III–V layer stacks on INP substrates using spectroscopic ellipsometry in the NIR spectral range

Thickness and complex refractive index of each layer in a double hetero structure, consisting of InP and InGaAsP, are obtained by spectroscopic ellipsometry. Accuracy is at least 2% in layer thickness and 0.005 in the refractive index of InP. An equation description of the complex refractive index allows for flexible description of InP-based materials in the wavelength range of 800–1700 nm. Simultaneous determination of thickness and refractive index by non-destructive ellipsometry in the near infra red (NIR) for the layers in a double hetero layer stack requires additional information on the properties of these layers

Analysis of optical surfaces by means of surface plasmon spectroscopy

The sensitivity to material parameters of surface plasmon oscillations is explored for the design of a prototype system operating at a wavelength of 670 nm, for the simultaneous determination of thickness, complex permittivity and surface roughness of metal films. The apparatus was employed for characterization of gold and silver films with thicknesses within the 10-100 nm range. Thickness data measured with the prototype system were well correlated with those measured on a conventional surface profilometer. The Fourier spectrum of surface irregularities extracted from scattered light, enhanced by surface plasmon oscillations, was used to determine surface roughness parameters for the distinct samples. Those parameters were shown to be representative of typical surface structures observed with the atomic force microscope.

The resonant ATR (attenuated total reflectance) approach to semiconductor diagnostics and its application to the depth-profiling of multilayer structures

The resonant ATR spectroscopy (attenuated total reflectance) approach is discussed as a way to enhance the sensitivity of optical measurements through the excitation of resonant modes. In particular, the application of the method to the depth profiling of a multilayer structure is considered. After reviewing some results which illustrate the sensitivity of the technique, its transfer to a manufacturing environment is discussed. Finally, preliminary wavelength ATR spectra which allow the simultaneous determination of thickness and composition of a multilayer structure are presented.