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Spectroscopic Ellipsometry of fluid and gel phase Lipid Bilayers in hydrated conditions
摘要： The biological membranes play a crucial role in the various biological processes due to their characteristic physical properties. The parameters such as membrane composition, thickness undulations, and the influence of external stimuli play a crucial role in the phase state behavior of biological membranes. The supported lipid bilayer (SLBs) systems closely represent cell membranes and are often studied to understand their behavior. In the current study, we have implemented spectroscopic Ellipsometry (SE) technique to explore the optical properties of various single component lipid bilayers having different phase state (fluid and gel) under hydrated or native conditions. The measurement of ellipsometric angles ψ and Δ were obtained from SE and were utilized to realize an explicit phase state dependence. Further, we obtained the thickness (t) and refractive index (n) by modeling of these SE results. These results were found to be inter-related to the phase state and lateral organization. The bilayer thickness is further verified against values obtained from coarse-grained molecular dynamics simulations. The proposed method was tested on various lipid bilayers under their native phase state at room temperature and was found to have a correlation with AFM measurements.
关键词： fluid phase,Optical properties,gel phase,Spectroscopic Ellipsometry,Lipid membranes,Phase state
更新于2025-09-23 15:23:52
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Preparation of high-quality stress-free (001) aluminum nitride thin film using a dual Kaufman ion-beam source setup
摘要： We proposed and demonstrated a preparation method of (001) preferentially oriented stress-free AlN piezoelectric thin films. The AlN thin films were deposited by a reactive sputtering technique at substrate temperatures up to 330 °C using a dual Kaufman ion-beam source setup. We deposited the AlN on Si (100), Si (111), amorphous SiO2, and a (001) preferentially oriented Ti thin film and compared their crystallographic, optical, and piezoelectric properties. The AlN thin films deposited on the (001) preferentially oriented Ti thin films have the highest crystallographic quality. The stress-free AlN reached a high value of the piezoelectric coefficient d33 = (7.33 ± 0.08) pC·N?1. The properties of the AlN thin film prepared at such low temperatures are suitable for numerous microelectromechanical systems, piezoelectric sensors, and actuators monolithically integrated with complementary metal-oxide-semiconductor signal-processing circuits.
关键词： Ellipsometry,Aluminum nitride thin film,Optical properties,d33 piezoelectric coefficient,Kaufman ion-beam source,Ion-beam sputtering deposition,(001) preferential orientation,X-ray diffraction
更新于2025-09-23 15:23:52
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New ellipsometric approach for determining small light ellipticities
摘要： Control of the coherent light polarization is always one of the important topics in laser physics and engineering. We propose an exact ellipsometric method for investigation of coherent light with small ellipticity. Using compensators with phase retardations providing maximum measurement accuracy for the selected ellipticity range is suggested. The method allows us to avoid taking into account the interference of multiple internal reflections of coherent light. The accuracy of the method increases with decreasing of the compensator phase retardation. Using light with a given ellipticity, we have measured the ellipticity of the light in the range of 3.5×10?? to 5.0×10?3. The relative error of the ellipticity measuring in the range of 8.0×10?? to 5.0×10?3 turns out does not exceed 0.02.
关键词： Polarization,Ellipsometry,Coherence
更新于2025-09-23 15:23:52
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The stability and degradation of PECVD fluoropolymer nanofilms
摘要： Fluoropolymer films are frequently used in microfabrication and for producing hydrophobic and low-k dielectric layers in various applications. As the reliability of functional coatings is becoming a more pressing issue in industry, it is necessary to determine the physical stability and degradation properties of this important class of films. To this end, a study has been undertaken to ascertain the aging characteristics of fluoropolymer films under various environmental conditions that such a film may experience during its use. In particular, fluorocarbon films formed by plasma-enhanced chemical vapour deposition (PECVD) using octafluorocyclobutane, or c-C4F8, as a precursor gas have been exposed to abrasive wear, elevated temperatures, ultraviolet radiation, as well as oxygen plasma and SF6 plasma, the latter being commonly used in conjunction with these films in ion etching processes. The results show that sub-micron thick fluoropolymer films exhibit a significant amount of elastic recovery during nanoscratch tests, minimising the impact of wear. The films exhibit stability when exposed to 365 nm UV light in air, but not 254 nm light in air, which generated significant decreases in thickness. Exposure to temperatures up to 175 °C did not generate loss of material, whereas temperatures higher than 175 °C did. Etching rates upon exposure to oxygen and SF6 plasmas were also measured.
关键词： Octafluorocyclobutane,Plasma deposition,Atomic force microscopy,Wear,Ellipsometry
更新于2025-09-23 15:23:52
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Metrology of Nanostructures by Tomographic Mueller-Matrix Scatterometry
摘要： The development of necessary instrumentation and metrology at the nanoscale, especially fast, low-cost, and nondestructive metrology techniques, is of great significance for the realization of reliable and repeatable nanomanufacturing. In this work, we present the application of a homemade novel optical scatterometer called the tomographic Mueller-matrix scatterometer (TMS), for the measurement of photoresist gratings. The TMS adopts a dual rotating-compensator configuration and illuminates the nanostructure sequentially under test conditions by a plane wave, with varying illumination directions and records. For each illumination direction, the polarized scattered field along various directions of observation can be seen in the form of scattering Mueller matrices. That more scattering information is collected by TMS than conventional optical scatterometry ensures that it achieves better measurement sensitivity and accuracy. We also show the capability of TMS for determining both grating pitch and other structural parameters, which is incapable by current zeroth-order methods such as reflectometry- or ellipsometry-based scatterometry.
关键词： inverse scattering,ellipsometry,pitch measurement,diffraction grating,scatterometry,Mueller matrix
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE 4th International Forum on Research and Technology for Society and Industry (RTSI) - Palermo, Italy (2018.9.10-2018.9.13)] 2018 IEEE 4th International Forum on Research and Technology for Society and Industry (RTSI) - Structural and Optical Behaviour of MAPbI<inf>3</inf> Layers in Nitrogen and Humid Air
摘要： The tendency of MA+-containing perovskites to degradation under humid air is still the main challenge which limits the durability of technologies. We indeed frame the behavior of MAPbI3 layer through structural and optical characterization under thermal cycles and using the environmental composition as a variable parameter (humid air, N2, Ar, O2). Within the temperature range explored (RT-80°C) we likely approach the thermal operation of the material under the sun and find that the degradation mechanism is linked to the action of water molecules by the formation of lattice defects. They rise the lattice disorder, especially at the crossover of the tetragonal to cubic transition wherein an acceleration of the degradation kinetics is observed. Nitrogen can help rationalizing solutions to stabilize the materials even at this critical transition step, since it behaves as more than an inert species.
关键词： Spectroscopic Ellipsometry,Photovoltaics,X-ray diffraction,Hybrid Perovskites,Stability,Thermal Cycle
更新于2025-09-23 15:22:29
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Optical response of heterogeneous polymer layers containing silver nanostructures
摘要： This work is focused on the study of the optical properties of silver nanostructures embedded in a polymer host matrix. The introduction of silver nanostructures in polymer thin films is assumed to result in layers having adaptable optical properties. Thin film layers with inclusions of differently shaped nanoparticles, such as nanospheres and nanoprisms, and of different sizes, are optically characterized. The nanoparticles are produced by a simple chemical synthesis at room temperature in water. The plasmonic resonance peaks of the different colloidal solutions range from 390 to 1300 nm. The non-absorbing, transparent polymer matrix poly(vinylpyrrolidone) (PVP) was chosen because of its suitable optical and chemical properties. The optical studies of the layers include spectrophotometry and spectroscopic ellipsometry measurements, which provide information about the reflection, transmission, absorption of the material as well as the complex optical indices, n and k. Finite difference time domain simulations of nanoparticles in thin film layers allow the visualization of the nanoparticle interactions or the electric field enhancement on and around the nanoparticles to complete the optical characterization. A simple analysis method is proposed to obtain the complex refractive index of nanospheres and nanoprisms in a polymer matrix.
关键词： nanospheres,thin film layers,plasmonic nanoparticles,nanoprisms,spectroscopic ellipsometry
更新于2025-09-23 15:22:29
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Ellipsometric Analysis of Aligned Carbon Nanotubes for Designing Catalytic Support Systems
摘要： Vertically aligned CNT carpets combined with inorganic semiconductors are expected good prospect in practical applications, especially in photocatalysis. If these devices are in production, a fast and non-invasive characterization method will be required. Ellipsometry is widely used in industry as an in-line monitoring tool, so in this study the applicability of ellipsometry for characterizing CNT carpets is investigated. It is shown that ellipsometric evaluation can provide information about the density and the optical properties of the nanotubes; however, the properties of the individual nanotubes (diameter, wall number) can not be taken into account during ellipsometric modeling. To overcome these limitations, numerical simulations are also presented.
关键词： Ellipsometry,Anisotropic Materials,CNT Synthesis
更新于2025-09-23 15:22:29
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Advanced Silicon Carbide Devices and Processing || Investigation of SiC/Oxide Interface Structures by Spectroscopic Ellipsometry
摘要： We have investigated SiC/oxide interface structures by the use of spectroscopic ellipsometry. The depth profile of the optical constants of thermally grown oxide layers on SiC was obtained by observing the slope-shaped oxide layers, and the results suggest the existence of the interface layers, around 1 nm in thickness, having high refractive index than those of both SiC and SiO2. The wavelength dispersions of optical constants of the interface layers were measured in the range of visible to deep UV spectral region, and we found the interface layers have similar dispersion to that of SiC, though the refractive indices are around 1 larger than SiC, which suggests the interface layers are neither transition layers nor roughness layers, but modified SiC, e.g., strained and/or modified composition. By the use of an in-situ ellipsometer, real-time observation of SiC oxidation was performed, and the growth rate enhancement was found in the thin thickness regime as in the case of Si oxidation, which cannot be explained by the Deal-Grove model proposed for Si oxidation. From the measurements of the oxidation temperature and oxygen partial pressure dependences of oxidation rate in the initial stage of oxidation, we have discussed the interface structures and their formation mechanisms within the framework of the interfacial Si-C emission model we proposed for SiC oxidation mechanism.
关键词： interface state density,SiC-MOSFET,SiC/oxide interface,SiC oxidation mechanism,spectroscopic ellipsometry
更新于2025-09-23 15:22:29
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Polydimethylsiloxane: Optical properties from 191 to 1688?nm (0.735–6.491?eV) of the liquid material by spectroscopic ellipsometry
摘要： Polydimethylsiloxane (PDMS) is an important polymer with numerous applications. Herein, the authors report the optical function(s) of PDMS from 191 to 1688 nm as determined from reflection spectroscopic ellipsometry (SE) and transmission ultraviolet-visible data. Two commercial samples of liquid PDMS (PDMS700 and PDMS2000) with molecular weights of 700–1500 g/mol and 2000–3500 g/mol, respectively, were analyzed. Both samples were linear polymers terminated with silanol groups. The optical functions determined from the two materials were essentially identical. Both the reflection and transmission measurements obtained from these materials required special experimental considerations. For the reflection SE measurements, these included roughening (frosting) the inside of the vessel that held PDMS and the need to level the instrument instead of the samples. The transmission measurements were obtained via a dual cuvette approach that eliminated the effects of the cuvettes and their interfaces. In addition to analyzing the data from the individual samples, the SE data from the samples were considered together in a multisample analysis (MSA). Because both samples of PDMS were transparent over the measured wavelength range, and because of the relatively wide wavelength range considered, the optical functions here were fit with Sellmeier models. This produced a good fit for the MSA with a mean squared error value of 1.68. The optical functions obtained in this work agreed well with previously reported values. For example, for the MSA, the authors obtained the following nx values, where x is the wavelength in nanometers: n300 = 1.443, n500 = 1.407, and n1000 = 1.393.
关键词： spectroscopic ellipsometry,optical properties,Sellmeier,transmission,optical function,polydimethylsiloxane (PDMS)
更新于2025-09-23 15:22:29