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In this paper, we present spectroscopic ellipsometry measurements of five selected bulk chalcogenide glasses (Ge 28 Sb 6 Se 66 , Ge 19 Sb 17 Se 64 , Ge 12 Sb 25 Se 63 , Ge 28 Sb 12 Se 60 and As 40 Se 60) for broad wavelength range (0.3–15 μm) at the temperatures from room temperature up to glass transition temperature (with reserve). Temperature dependence of bandgap energy obtained from Tauc-Lorentz oscillator together with temperature dependence of refractive index for selected wavelengths (1.55, 3.4, 7.0 and 10.6 μm) where the studied materials are transparent are presented together with thermo-optic coefficients d E g /d T and d n /d T for these wavelengths. [ABSTRACT FROM AUTHOR]

The application of variable angle spectroscopic ellipsometry (VASE) to the characterization of thin films is very important because it facilitates the understanding of their physical and optical properties. To prepare a series of film samples consisting of TiO2:ZrO2 on a TiN/Si substrate, we employed the SYBILLA P200 equipment (manufactured by ABCD Technology) through the process of Chemical Beam Vapor Deposition (CBVD). TiO2:ZrO2 on TiN/Si thin films is a composite material that has gained significant attention in various technological applications, particularly in the field of thin film coatings on semiconductor substrates like TiN/Si. TiO2:ZrO2 thin films exhibit excellent dielectric properties and good thermal stability, making them suitable for various electronic and semiconductor applications. From FESEM and EDX analysis, it is found that with increase of Ti/Zr atomic ratio, grain size increases. Ellipsometric analysis reveals increase in film thickness and refractive index with increase in Ti/Zr atomic ratio. As the film continues to grow, changes in its microstructural phase led to a transition from a monolayer physical ellipsometry model to a bilayer physical model. This transition is due to the appearance of inhomogeneity in the TiO2:ZrO2 thin film. Dynamic fits obtained using a two‐layer physical model and a Cauchy–Lorentz optical model show three distinct phases in the film growth phase: a nucleation phase, a fusion phase, and a continuous layer phase. Although our proposed model shows satisfactory performance in most cases, the determination of the refractive index can be problematic for very thin thicknesses. The developed VASE modeling process should be able to generate TiO2:ZrO2characterization on TiN/Si substrate films using comparable physical and optical modeling considerations. [ABSTRACT FROM AUTHOR]

The research referred to in this study examines the morphological, structural, and optical characteristics of kesterite (Cu1−xAgx)2ZnSnS4 (CAZTS) thin films, which are produced using a process known as thermal evaporation (TE). The study's main goal was to determine how different Ag contents affect the characteristics of CAZTS systems. X-ray diffraction (XRD) and Raman spectroscopy were used to confirm the crystal structure of the CAZTS thin films. Using a mathematical model of spectroscopic ellipsometry, the refractive index (n) represented the real part of the complex thin films, the extinction coefficient (k) portrayed the imaginary part, and the energy bandgap of the fabricated thin films was calculated. The energy bandgap is a crucial parameter for solar cell applications, as it determines the wavelength of light that the material can absorb. The energy bandgap was found to decrease from 1.74 eV to 1.55 eV with the increasing Ag content. The ITO/n-CdS/p-CAZTS/Mo heterojunction was well constructed, and the primary photovoltaic characteristics of the n-CdS/p-CAZTS junctions were examined for use in solar cells. Different Ag contents of the CAZTS layers were used to determine the dark and illumination (current–voltage) characteristics of the heterojunctions. The study's findings collectively point to CAZTS thin layers as potential absorber materials for solar cell applications. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) thin films prepared by the sol–gel technique have been shown to be optically isotropic and, unlike the films obtained by competitive methods, do not exhibit measurable birefringence. A series of submicrometer-thin titanium dioxide films were prepared using the sol–gel technique and then thermally annealed at different temperatures. The samples were analyzed by spectroscopic ellipsometry using the Mueller matrix formalism, X-ray diffractometry and scanning electron microscopy. The conversion of amorphous titanium dioxide to polycrystalline anatase occurred at 400 °C or higher. Crystallites of a few percent of the film thickness were observed. Nevertheless, the crystallization process did not trigger the appearance of birefringence. These observations demonstrate that high-quality planar optical waveguides can be successfully fabricated on flexible substrates, in particular those composed of efficient polymers that can withstand the aforementioned temperatures. [ABSTRACT FROM AUTHOR]

Hybrid strategies that combine conventional top-down lithography with bottom-up molecular assembly are of interest for a range of applications including nanolithography and sensors. Interest in these strategies stems from the ability to create complex architectures over large areas with molecular-scale control and precision. The molecular-ruler process typifies this approach where the sequential layer-by-layer assembly of mercaptoalkanoic acid molecules and metal ions are combined with conventional top-down lithography to create precise, registered nanogaps. However, the quality of the metal-ligated mercaptoalkanoic acid multilayer is a critical characteristic in generating reproducible and robust nanoscale structures via the molecular-ruler process. Therefore, we explore the assembly of alkanethiolate monolayers, mercaptohexadecanoic acid (MHDA) monolayers, and Cu-ligated MHDA multilayers on Au{111} substrates using atomic force microscopy and in situ dynamic spectroscopic ellipsometry. The chemical film thicknesses in situ dynamic spectroscopic ellipsometry agree with previous ex situ surface analytical methods. Moreover, in situ dynamic spectroscopic ellipsometry provides insight into the assembly process without interrupting the assembly process and potentially altering the characteristics of the resulting chemical film. By following the real-time dynamics of each deposition step, the assembly of the Cu-ligated MHDA multilayers can be optimized to minimize deposition time while having minimal impact to the quality of the chemical film. [ABSTRACT FROM AUTHOR]

Abstract The silicon suboxide SiOx (x

Porous semiconductors have garnered significant attention owing to their distinctive physical and chemical properties. In this study, optical anisotropy is presented in porous germanium (PGe) on a Si (001) substrate. Both n‐ and p‐type PGe, achieved through bipolar electrochemical etching, exhibit optical anisotropy along the Ge <001> direction, as determined by spectroscopic ellipsometry. Birefringence and depolarization factors are controllable by adjusting the etching parameters and doping concentration of the epitaxial Ge layer. The gradient porosity and pore distribution in PGe can be well captured by the optical models. The findings of optical anisotropy in PGe‐on‐Si hold promise for applications in optical elements or sensors for gas or biomolecules. [ABSTRACT FROM AUTHOR]

Perfect absorbers, widely utilized in solar energy‐harvesting devices, optical communications, sensors, displays, and filters, achieve 100% light absorption. However, perfect absorbers employing micro/nanostructures encounter challenges such as high cost and complexity in simulation and fabrication. Here, novel wavelength‐linearly‐dependent and polarization‐sensitive perfect absorbers utilizing optically anisotropic germanium selenide (GeSe) are proposed. A simple and cost‐effective GeSe‐SiO2‐Si multilayered optical thin film is constructed and optimized to achieve destructive interference, leading to perfect absorption. The operating wavelength can be linearly tuned from 900 nm to 1300 nm by adjusting the GeSe thickness from 125 nm to 200 nm. Leveraging the significant optical anisotropy, the polarization angle is introduced as an additional parameter to dynamically and finely control the operating wavelength, enabling the creation of polarization‐sensitive perfect absorbers. Experimental results validate the feasibility of fabricating and dynamically modulating the proposed wavelength‐linearly‐dependent and polarization‐sensitive perfect absorbers. This study introduces a novel approach for designing and fabricating reconfigurable perfect absorbers utilizing low‐symmetry materials, facilitating mass production and on‐chip integrated systems. [ABSTRACT FROM AUTHOR]

We report the temperature dependences of the dielectric function ε = ε1 + iε2 and critical point (CP) energies of the uniaxial crystal GaSe in the spectral energy region from 0.74 to 6.42 eV and at temperatures from 27 to 300 K using spectroscopic ellipsometry. The fundamental bandgap and strong exciton effect near 2.1 eV are detected only in the c-direction, which is perpendicular to the cleavage plane of the crystal. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that incorporates the Bose–Einstein statistical factor and the temperature coefficient to describe the electron–phonon interaction. To determine the origin of this anisotropy, we perform first-principles calculations using the mBJ method for bandgap correction. The results clearly demonstrate that the anisotropic dielectric characteristics can be directly attributed to the inherent anisotropy of p orbitals. More specifically, this prominent excitonic feature and fundamental bandgap are derived from the band-to-band transition between s and pz orbitals at the Γ-point. [ABSTRACT FROM AUTHOR]

Gallium telluride thin films have emerged as a promising material for various electronic and optoelectronic applications due to their unique properties. In this study, we investigate the growth of nanometer-thick GaTe films on sapphire substrates using molecular beam epitaxy and explore the influence of the growth temperature on the structural, electronic, and optical properties of the films. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman measurements are employed to characterize the structural quality of the films, while spectroscopy ellipsometry provides insights into their electronic and optical behavior. Our findings demonstrate that a higher temperature (500 °C) is the optimized growth temperature, which significantly impacts the quality and properties of GaTe thin films, making it a critical parameter for optimizing their performance in electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this study, the optical behavior of lead‐free Bi‐based low‐dimensional perovskite single crystals (Cs3Bi2Cl9, Cs3Bi2Br9, Cs3Bi2I9, and MA3Bi2I9) is investigated by spectroscopic ellipsometry, supported by X‐ray diffraction and density functional theory calculations. All materials exhibit a strong excitonic peak resulting from photogenerated electron–hole Coulomb interactions, whereas the threshold of continuous absorption is found at higher energies. The resonances of the excitonic and continuous bands, along with exciton binding energies, are extracted through Critical Point Analysis of the ellipsometric data over a wide temperature range (from −90 °C to 90 °C), revealing subtle variations in the optical characteristics for each single crystal. These materials can be applied in optoelectronics as photodetectors because of their high stability and lower toxicity compared to their Pb‐based perovskites. [ABSTRACT FROM AUTHOR]

In order to model the propagation of light through a sand cloud, it is critical to have accurate data for the optical constants of the sand particles that comprise it. The same holds true for modeling propagation through particles of any type suspended in a medium. Few methods exist, however, to measure these quantities with high accuracy. In this paper, a characterization method based on spectroscopic ellipsometry (SE) that can be applied to a particulate material is presented. In this method, a polished disc of an adhesive compound is prepared, and its optical constants are measured. Next, a mixture of the adhesive and a sand sample is prepared and processed into a polished disc, and SE is performed. By treating the mixture as a Bruggeman effective medium, the optical constants of the particulate material are extracted. For verification of the proposed method, it is first applied to pure silica powder, demonstrating good agreement between measured optical constants and literature values. It is then applied to Arizona road dust, a standard reference material, as well as real desert sand samples. The resulting optical constant data is input into a rigorous scattering model to predict extinction coefficients for various types of sand. Modeling results are compared to spectroscopic measurements on static sand samples, demonstrating good agreement between predicted and measured spectral properties including the presence of a Christiansen feature near a wavelength of 8 µm. [ABSTRACT FROM AUTHOR]

Background: Stress measurement for thin films is crucial in a variety of fields such as in semiconductor manufacturing, the optoelectronics industry, and biomedical science, among others. However, most measurement methods require surface treatment of the thin film. Objective: A label-free measurement method for plane stress states in optical isotropic thin films based on spectroscopic ellipsometry analysis is proposed and verified in this paper. Methods: The proposed method is based on the modulation of the stress-optic effect on reflected spectroscopic ellipsometry. A theoretical model is established to describe the relation between all components of the plane-stress state and the classic ellipsometric parameters (Ψ, Δ). An algorithm is developed to determine all components of a plane-stress state by fitting the model to the experiment data. Results: In the verification experiment, we determined the plane stress state of a Cu film coated on a PI (polyimide) substrate. The results show a reasonable agreement between the experimental measurements from spectroscopic ellipsometry and the theoretical analysis based on the applied loading. Conclusion: The results prove that our method can effectively measure the plane stress state of optical isotropic thin films. [ABSTRACT FROM AUTHOR]

This work presents a combined optical and magneto‐optical spectroscopic study of thulium iron garnet (Tm3Fe5O12, TmIG) films on substituted gadolinium gallium garnet (Gd2.6Ca0.4Ga4.1Mg0.25Zr0.65O12, sGGG) substrates. Spectroscopic ellipsometry, transmission spectroscopy, magneto‐optical Kerr effect spectroscopy and Raman spectroscopy results are presented for TmIG films with a thickness in the range from 20 to 300 nm grown on sGGG by pulsed laser deposition. The complex dielectric functions of TmIG and sGGG are determined and compared with previously published results for bulk yttrium iron garnet and GGG, respectively. The magneto‐optical spectroscopy corroborated with Raman spectroscopy sheds light on strain‐induced changes as a function of TmIG film thickness. [ABSTRACT FROM AUTHOR]

As a non-destructive and rapid technique, optical scatterometry has gained widespread use in the measurement of film thickness and optical constants. The recent advances in deep learning have presented new and powerful approaches to the resolution of inverse scattering problems. However, the application of deep-neural-network-assisted optical scatterometry for nanostructures still faces significant challenges, including poor stability, limited functionalities, and high equipment requirements. In this paper, a novel characterization method is proposed, which employs deep-neural-network-assisted ellipsometry to address these challenges. The method processes ellipsometric angles, which are measured by basic ellipsometers, as functional signals. A comprehensive model is developed to profile nano-gratings fabricated by diverse techniques, by incorporating rounded corners, residual layers, and optical constants into an existing model. The stability of the model is enhanced by implementing several measures, including multiple sets of initial values and azimuth-resolved measurements. A simple compensation algorithm is also introduced to improve accuracy without compromising efficiency. Experimental results demonstrate that the proposed method can rapidly and accurately characterize nano-gratings fabricated by various methods, with relative errors of both geometric and optical parameters well controlled under 5 %. Thus, the method holds great promise to serve as an alternative to conventional characterization techniques for in-situ measurement.

The Ge x Sb 30-x Se 70 : x = 30, 25, 15, 10 glass films were prepared by thermal evaporation technique. The surface morphology of glass films was studied by atomic force microscopy. The samples exhibited surface roughness with a root mean square value falling within the 0.89–1.47 nm range. The optical properties were precisely characterized by spectroscopic ellipsometry in the 4.13–0.77 eV spectral range. The Cody-Lorentz dispersion model was used to fit the data across the entire spectral range and extract the optical functions of glass films. It has been observed that the refractive index, n values rise with increasing energy, reaching a peak, and then experience a subsequent decline. The refractive index values exhibit a rising trend with an increase in Sb content. The optical bandgap, E g opt was found to follow a decreasing pattern with a decrease in Ge content. The refractive index dispersion curve was analyzed using the Wemple and DiDomenico single oscillator model in the lower absorption spectral region. It has been observed the values of oscillator energy, E o, and static refractive index, n 0, exhibit a pattern consistent with that of E g opt , and n, respectively. The optical properties, such as the high-frequency dielectric constant, carrier concentration, plasma frequency, and optical conductivity were analyzed. [ABSTRACT FROM AUTHOR]

Ellipsometry is widely used to determine the thermo-optical properties of thin polymer films. However, if the thermo-optic coefficient (TOC) and the linear thermal expansion coefficient (LTEC) are to be used to determine the temperature coefficient of electronic polarizability (TCEP) in thin polymer films, their values must be determined with the greatest possible accuracy, as both have the opposite effect. In this article, we analyze changes in ellipsometric parameters resulting from changes in the thin film temperature in order to develop a data analysis method for temperature-dependent spectroscopic ellipsometry that will facilitate the accurate determination of thermo-optical parameters, including the TCEP, in polymer thin films. As practical application examples, we identified optimal spectral windows to accurately determine the thermo-optical parameters of 50 to 150 nm-thick PMMA thin films deposited on Si and SiO2 substrates. The influence of thin-film thickness on the accuracy of TOC and LTEC determination is discussed. [ABSTRACT FROM AUTHOR]

Development of ultrathin film (utf) hydrogels for cutting‐edge biomedical applications (i.e. artificial skins) is receiving increasing attention. Nonetheless, achieving accurate control on the structure and thickness of utf‐hydrogels becomes extremely complex when assessed through conventional techniques. In this work, an atmospheric‐pressure plasma‐assisted deposition technique is reported, showing great thickness accuracy and versatility, to design utf‐hydrogels with customized properties. For the first time, specific and independent control on the generation and nature of cross‐links by only changing the plasma exposure frequency (fPE) during the synthesis process are reported. Thus, utf‐hydrogels are successfully prepared with tuned swelling ratios and viscoelastic properties (ranging from 150 to 20 kPa). Moreover, a thickness accuracy of 9 nm is reported, permitting the accurate synthesis of utf‐hydrogels below 150 nm. Exhaustive structural and topographical analyses allow elucidating the effects of the fPE on the cross‐link generation mechanism, discarding any undesired effect on the thickness accuracy. To support the structural results obtained, quartz‐crystal microbalance with dissipation (QCM‐D) coupled with spectroscopic ellipsometry are put in the spotlight as an efficient and viable alternative for the characterization of the resulting properties of ultrathin film soft materials, including the presence of a hydrated layer at the interface. [ABSTRACT FROM AUTHOR]

In this paper, we have performed a study on the optical properties of single crystals ZnGa2S4 by method of density functional theory (DFT) and ellipsometry measurements. The calculated results for the real ε r and imaginary ε i parts of the dielectric function are compared with the measured experimental spectroscopic ellipsometry (SE) spectra in the 0.7–6.5 eV spectral region. Absorption coefficient-photon energy dependency revealed the existence of direct bandgap transitions with energy 3.5 eV. This result is very close to bandgap obtained from our theoretical calculation. [ABSTRACT FROM AUTHOR]

In this paper, we have performed a study on the optical properties of single crystals ZnGa2S4 by method of density functional theory (DFT) and ellipsometry measurements. The calculated results for the real ε r and imaginary ε i parts of the dielectric function are compared with the measured experimental spectroscopic ellipsometry (SE) spectra in the 0.7–6.5 eV spectral region. Absorption coefficient-photon energy dependency revealed the existence of direct bandgap transitions with energy 3.5 eV. This result is very close to bandgap obtained from our theoretical calculation. [ABSTRACT FROM AUTHOR]

Copper-nitride (Cu 3 N) semiconductor material is attracting much attention as a potential, next-generation thin-film solar light absorber in solar cells. In this communication, polycrystalline covalent Cu 3 N thin films were prepared using reactive-RF-magnetron-sputtering deposition, at room temperature, onto glass and silicon substrates. The very-broadband optical properties of the Cu 3 N thin film layers were studied by UV-MIR (0.2–40 μ m) ellipsometry and optical transmission, to be able to achieve the goal of a low-cost absorber material to replace the conventional silicon. The reactive-RF-sputtered Cu 3 N films were also investigated by focused ion beam scanning electron microscopy and both FTIR and Raman spectroscopies. The less dense layer was found to have a value of the static refractive index of 2.304, and the denser film had a value of 2.496. The iso-absorption gap, E 04 , varied between approximately 1.3 and 1.8 eV and could be considered suitable as a solar light absorber. [ABSTRACT FROM AUTHOR]

Spectroscopic ellipsometry is a reproducible and non-invasive characterization technique that allows the evaluation of multilayered structures. However, it is an indirect technique and requires the use of well-calibrated models to correctly analyze the materials. In this work, we report a multilayer modeling approach to investigate the optical properties of the three layers of interest typically employed on an inverted perovskite solar cells structure, namely, indium-tin-oxide (ITO) as a transparent anode, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as a hole transport layer, and methylammonium lead iodide (MAPbI3) as the perovskite layer. The parameterized optical constants based on oscillator models were simultaneously fitted to ellipsometry and intensity-transmission data and validated with ultraviolet–visible (UV–Vis) spectroscopy and profilometry. We propose this multilayer modeling approach as a method to be employed throughout the different stages of the fabrication process to study the distinct mechanisms that impact the final performance of a photovoltaic device.

The research referred to in this study examines the morphological, structural, and optical characteristics of kesterite (Cu1−xAgx)2ZnSnS4 (CAZTS) thin films, which are produced using a process known as thermal evaporation (TE). The study’s main goal was to determine how different Ag contents affect the characteristics of CAZTS systems. X-ray diffraction (XRD) and Raman spectroscopy were used to confirm the crystal structure of the CAZTS thin films. Using a mathematical model of spectroscopic ellipsometry, the refractive index (n) represented the real part of the complex thin films, the extinction coefficient (k) portrayed the imaginary part, and the energy bandgap of the fabricated thin films was calculated. The energy bandgap is a crucial parameter for solar cell applications, as it determines the wavelength of light that the material can absorb. The energy bandgap was found to decrease from 1.74 eV to 1.55 eV with the increasing Ag content. The ITO/n-CdS/p-CAZTS/Mo heterojunction was well constructed, and the primary photovoltaic characteristics of the n-CdS/p-CAZTS junctions were examined for use in solar cells. Different Ag contents of the CAZTS layers were used to determine the dark and illumination (current–voltage) characteristics of the heterojunctions. The study’s findings collectively point to CAZTS thin layers as potential absorber materials for solar cell applications.

Titanium dioxide (TiO2) thin films prepared by the sol–gel technique have been shown to be optically isotropic and, unlike the films obtained by competitive methods, do not exhibit measurable birefringence. A series of submicrometer-thin titanium dioxide films were prepared using the sol–gel technique and then thermally annealed at different temperatures. The samples were analyzed by spectroscopic ellipsometry using the Mueller matrix formalism, X-ray diffractometry and scanning electron microscopy. The conversion of amorphous titanium dioxide to polycrystalline anatase occurred at 400 °C or higher. Crystallites of a few percent of the film thickness were observed. Nevertheless, the crystallization process did not trigger the appearance of birefringence. These observations demonstrate that high-quality planar optical waveguides can be successfully fabricated on flexible substrates, in particular those composed of efficient polymers that can withstand the aforementioned temperatures.

Asphalt pavement possesses the characteristics of strong sunlight absorption, which lead to the aging of asphalt binder. Asphalt aging is one of the leading causes of the performance deterioration in the asphalt pavement, and the appearance of crystalline wax (paraffin wax) during aging has a significant effect on optical properties (absorption and reflection) of the asphalt binder. In this paper, effects of the crystalline wax on optical properties of the asphalt binder were investigated using the spectroscopic ellipsometry (SE) technique, and a new method for the quantification of the crystalline wax in asphalt was also developed. Cold Lake asphalt doped with different contents of n-alkanes (eicosane, triacontane, and tetracontane) were tested by the SE. The results showed that there is a close linear relationship between the optical constants and wax content of the asphalt binder. In addition, with increasing both the chain length of n-alkanes and their content, the reflection intensity of the asphalt binder decreased, and the refractive index and extinction coefficient increased accordingly. On the whole, ellipsometry-based optical testing is a promising method for rapid and non-destructive identification of wax in asphalt. [ABSTRACT FROM AUTHOR]

We review the measurement methods and thickness characterization algorithms of semiconductor multilayer devices. Today’s ultrahigh-density, high-energy-efficient three-dimensional semiconductor devices require an iterative semiconductor layer-stacking process. Accurate determination of nanometer-scale layer thickness is crucial for reliable semiconductor device fabrication. In this paper, we first review the commonly used semiconductor multilayer thickness measurement methods, including destructive and nondestructive measurement methods. Next, we review two approaches for thickness characterization: model-based algorithms using a physical interpretation of multilayer structures and a method using data-driven machine learning. With the growing importance of semiconductor multilayer devices, we anticipate that this study will help in selecting the most appropriate method for multilayer thickness characterization.Highlights: This paper covers various measurement methods and algorithms to detect the thickness of semiconductor multilayer devices. Model-based algorithm is suitable for cases where the number of layers is small or physical interpretation is required. Machine learning performs well for thickness characterization of multilayer devices without complex physical analysis. [ABSTRACT FROM AUTHOR]

The high-quality aluminum nitride (AlN) epilayer is the key factor that directly affects the performance of semiconductor deep-ultraviolet (DUV) photoelectronic devices. In this work, to investigate the influence of thickness on the quality of the AlN epilayer, two AlN-thick epi-film samples were grown on c-plane sapphire substrates. The optical and structural characteristics of AlN films are meticulously examined by using high-resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM), a dual-beam ultraviolet-visible spectrophotometer, and spectroscopic ellipsometry (SE). It has been found that the quality of AlN can be controlled by adjusting the AlN film thickness. The phenomenon, in which the thicker AlNn film exhibits lower dislocations than the thinner one, demonstrates that thick AlN epitaxial samples can work as a strain relief layer and, in the meantime, help significantly bend the dislocations and decrease total dislocation density with the thicker epi-film. The Urbach's binding energy and optical bandgap (Eg) derived by optical transmission (OT) and SE depend on crystallite size, crystalline alignment, and film thickness, which are in good agreement with XRD and SEM results. It is concluded that under the treatment of thickening film, the essence of crystal quality is improved. The bandgap energies of AlN samples obtained from SE possess larger values and higher accuracy than those extracted from OT. The Bose–Einstein relation is used to demonstrate the bandgap variation with temperature, and it is indicated that the thermal stability of bandgap energy can be improved with an increase in film thickness. It is revealed that when the thickness increases to micrometer order, the thickness has little effect on the change of Eg with temperature. [ABSTRACT FROM AUTHOR]

The thermal properties and alignment of crystallinity of materials in thin films play crucial roles in the performance and reliability of various devices, especially in the fields of electronics, materials science, and engineering. The slight variations in the molecular packing of the active layer can make considerable differences in the optical and thermal properties. Herein, we aim to investigate the tuning of the physical properties of a blended thin film of n-type small organic molecules of perylene-3,4,9,10-tetracarboxylic acid (PTCA-SMs) with the mixing of the p-type polymer poly(3-hexylthiophene) (P3HT). The resulting thin films exhibit an enhanced surface crystallinity compared to the pristine material, leading to the formation of long crystallites, and these crystallites are thermally stable in the solid state, as confirmed by X-ray diffraction (XRD), atomic force microscopy (AFM), and thermal analysis using variable-temperature spectroscopic ellipsometry (VTSE) and differential scanning calorimetry (DSC). We believe that the crystalline structure of the obtained P3HT/PTCA-SMs blends is a combination of edge-on and face-on orientations, which enable the potential use of this material as an active layer in organic electronics. [ABSTRACT FROM AUTHOR]

A pure experiment-based work was conducted to investigate the optical characteristics of a thin absorbing singlelayer copper film at various annealing temperatures. The study also systematically examined the utilization of spectroscopic ellipsometry as an effective tool for fine-tuning the optical constants of thin films, particularly for achieving specific refractive index (n) and extinction coefficient (k) values. The measurement and analysis involved a thermally deposited thin nanosized single-layer copper film on a glass substrate, along with a spectroscopic ellipsometer. [ABSTRACT FROM AUTHOR]

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Silver (Ag) thin films have garnered significant attention due to their unique optical properties. This paper systematically investigates the optical characteristics of Ag films prepared using the electron beam evaporation method. The investigation was conducted using spectroscopic ellipsometry and covers a broad wavelength range of 1679 nm to 36 µm (0.738–0.034 eV), spanning from near-infrared to far-infrared regions. Optical and dispersion models were developed to analyze the impacts of Ag nanostructures on the complex refractive indices, dielectric functions, and reflectance. The results indicate that Ag particles and coalescence films exhibit non-metallic and low absorption properties, while Ag percolation and continuous films present a typical Drude model. The reflectance of Ag films increases as the film coverage ratio increases, and it can reach close to 100% in continuous film. Additionally, a non-destructive, non-contact, and vacuum-free means of confirming the percolation threshold of Ag films was proposed based on the slope of the imaginary part curve. This work is useful to guide simulations and provide a basis for the applications of Ag films in different fields. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study of a titanium–platinum thin film-based electrode preparation and its practical application in the electrooxidation of cyanides to help protect our environment. The novel electrochemical deposition process of Pt on nearly atomically smooth magnetron-sputtered Ti film has been used to prepare a highly effective glass|Ti|Pt composite electrode with high catalytic activity for the electrooxidation of cyanide ions. The composite electrode exhibits over a 90% electrical current efficiency in the cyanide electrooxidation process and can be used for the decontamination of highly concentrated KCN solutions (up to 0.1 M) without any chemical additives. A high current efficiency (70%) of Pt thin film deposition on a glass|Ti electrode was achieved using a potentiostatic double-pulse method. Fast Fourier transform electrochemical impedance spectroscopy revealed the oxidation kinetics for cyanide ions at the electrode. The glass|Ti electrode was prepared using the magnetron sputtering technique, which allows us to fabricate electrodes of any shape suitable for any electrochemical cell or electroplating bath. Meanwhile, electrochemical deposition of Pt on the glass|Ti electrode is an efficient and environmentally friendly method, since various salts of Pt and/or Pt-containing wastes can be used for electrodeposition instead of pure Pt, which is more expensive. [ABSTRACT FROM AUTHOR]

In this study, SnTe thin films were successfully synthesized through thermal evaporation, and the films were characterized, with a particular emphasis on the use of spectroscopic ellipsometry (SE). The structural properties of the SnTe thin films were investigated by employing grazing incidence x-ray diffraction (GI-XRD), which indicated that the films exhibited polycrystalline growth. The thickness and density of the film were estimated to be approximately 31 nm and 6.24 g/cm3, respectively, by analyzing the Kiessig fringe pattern obtained from x-ray reflectivity (XRR). Raman spectroscopy revealed the longitudinal optical (LO) and transverse optical (TO) modes, with a small red shift in peak positions due to the quantum confinement effect. A comparative analysis revealed that the Raman modes in the SnTe thin film were red-shifted compared to those in the bulk SnTe powder, which may be attributed to the nanometer size effect. The optical properties, studied in the wavelength range of 300–1000 nm using SE, showed that the film's refractive index (n) decreases while the extinction coefficient (k) first increases and then gradually decreases with increasing photon energy. The spectral signature of the extinction coefficient (k) indicated an increase in photon absorption in the near-infrared (NIR) region. Moreover, the optical conductivity (σopt) plot showed an improved optical response in the vicinity of 1.40 eV in the NIR range. The direct transition optical bandgap ( E opt g ) obtained for the SnTe thin films was 1.20 eV, and this, along with the better optical response, suggests the potential application of the films for NIR detection. [ABSTRACT FROM AUTHOR]

The creation of novel approaches to reduce the icing of devices is of economic, technical, and ecological interest. Passive deicing approaches based on thin polymer layers show high potential. (Super)hydrophilic films, characterized by high swelling and surface energy, exhibit a self‐lubricating interfacial layer that can influence ice adhesion. For this purpose, a polymer layer consisting of zwitterionic 2‐methacryloyloxyethyl phosphorylcholine (MPC) and glycidyl methacrylate (GMA) is presented and investigated with respect to its icing behavior. The dependence of the swelling behavior of these layers on temperature and a stabilization of the swelling even at low temperatures is shown and can be directly influenced by the grafting conditions, which have a significant impact on the resulting ice thickness and deicing performance. In addition to the formation of a thinner ice layer, the polymer coatings grafted for 16 h are characterized by excellent deicing performance, resulting in consistently very low ice layer thicknesses in repeated icing–deicing cycles compared to the investigated reference SiO2. Due to these properties, the developed film has high application potential as a coating for heat exchangers, as it enables a reduction of the time between defrosting cycles and the distance between the plates, resulting in energy and material savings. [ABSTRACT FROM AUTHOR]

Germanium (Ge) nanostrip was embedded in a polymer and studied as a waveguide. The measurements reveal that this new type of semiconductor/polymer heterogeneous waveguide exhibits strong absorption for the TE mode from 1500 nm to 2004 nm, while the propagation loss for the TM mode declines from 20.56 dB/cm at 1500 nm to 4.89 dB/cm at 2004 nm. The transmission characteristics serve as an essential tool for verifying the optical parameters (n-κ, refractive index, and extinction coefficient) of the strip, addressing the ambiguity raised by spectroscopic ellipsometry regarding highly absorbing materials. Furthermore, the observed strong absorption for the TE mode at 2004 nm is well beyond the cut-off wavelength of the crystalline bulk Ge (~1850 nm at room temperature). This redshift is modeled to manifest the narrowing of the Tauc-fitted bandgap due to the grain order effect in the amorphous Ge layer. The accurate measurement of the nanometer-scale light-absorbing strips in a waveguide form is a crucial step toward the accurate design of integrated photonic devices that utilize such components. [ABSTRACT FROM AUTHOR]

The most promising lead‐free options for producing perovskite solar cells are tin halide perovskite materials. Herein, while in situ monitoring the optical evolution of the material in humid air, spectroscopic ellipsometry is used to investigate the dielectric function of FASnI3 layers (with and without additives) within the range of 1–5 eV. According to calculations based on the density functional theory that shows oxygen diffusion on FASnI3 surfaces, the steady decrease in absorption coefficient in the band gap region (1.47 eV) and simultaneous increase in absorption in the 3–4.5 eV region suggest the production of amorphous tin oxide. Concurrently, X‐ray diffraction reveals a clear degradation of FASnI3. With the addition of sodium borohydride and dipropylammonium iodide, the optically active area of about 1.47 eV is preserved for a longer period while SnO2 production is prevented. Last but not least, FASnI3's stability is investigated in dry N2 environment and shown that it is optically durable for thermal operations up to 100 °C, particularly when additives are used. [ABSTRACT FROM AUTHOR]

MXenes, a family of 2D transition‐metal carbides and nitrides, have excellent electrical conductivity and unique optical properties. However, MXenes oxidize in ambient conditions, which is accelerated upon heating. Intercalation of water also causes hydrolysis accelerating oxidation. Developing new tools to readily characterize MXenes' thermal stability can enable deeper insights into their structure–property relationships. Here, in situ spectroscopic ellipsometry (SE) is employed to characterize the optical properties of three types of MXenes (Ti3C2Tx, Mo2TiC2Tx, and Ti2CTx) with varied composition and atomistic structures to investigate their thermal degradation upon heating under ambient environment. It is demonstrated that changes in MXene extinction and optical conductivity in the visible and near‐IR regions correlate well with the amount of intercalated water and hydroxyl termination groups and the degree of oxidation, measured using thermogravimetric analysis. Among the three MXenes, Ti3C2Tx and Ti2CTx, respectively, have the highest and lowest thermal stability, indicating the role of transition‐metal type, synthesis route, and the number of atomic layers in MXene flakes. These findings demonstrate the utility of SE as a powerful in situ technique for rapid structure–property relationship studies paving the way for the further design, fabrication, and property optimization of novel MXene materials. [ABSTRACT FROM AUTHOR]

Color etching is a useful corrosive process, widely applied in metallography to study the microstructure of metals. To prove the existence of the previously hypothesized steady-state etching rate, in-situ investigations were performed with spectroscopic ellipsometry during the color etching of ferritic materials. Kinetic information regarding the refractive index, extinction coefficient, and layer thickness were used to calculate the steady-state layer buildup rate, which was 1.90 ± 0.15 nm/s for low-carbon steel and 0.99 ± 0.06 nm/s for cast iron owing to its better corrosion resistance. The presented methodology and findings could help understanding other processes that involve the development of layers on metallic surfaces.

Abstract Development of ultrathin film (utf) hydrogels for cutting‐edge biomedical applications (i.e. artificial skins) is receiving increasing attention. Nonetheless, achieving accurate control on the structure and thickness of utf‐hydrogels becomes extremely complex when assessed through conventional techniques. In this work, an atmospheric‐pressure plasma‐assisted deposition technique is reported, showing great thickness accuracy and versatility, to design utf‐hydrogels with customized properties. For the first time, specific and independent control on the generation and nature of cross‐links by only changing the plasma exposure frequency (fPE) during the synthesis process are reported. Thus, utf‐hydrogels are successfully prepared with tuned swelling ratios and viscoelastic properties (ranging from 150 to 20 kPa). Moreover, a thickness accuracy of 9 nm is reported, permitting the accurate synthesis of utf‐hydrogels below 150 nm. Exhaustive structural and topographical analyses allow elucidating the effects of the fPE on the cross‐link generation mechanism, discarding any undesired effect on the thickness accuracy. To support the structural results obtained, quartz‐crystal microbalance with dissipation (QCM‐D) coupled with spectroscopic ellipsometry are put in the spotlight as an efficient and viable alternative for the characterization of the resulting properties of ultrathin film soft materials, including the presence of a hydrated layer at the interface.

Hybrid strategies that combine conventional top-down lithography with bottom-up molecular assembly are of interest for a range of applications including nanolithography and sensors. Interest in these strategies stems from the ability to create complex architectures over large areas with molecular-scale control and precision. The molecular-ruler process typifies this approach where the sequential layer-by-layer assembly of mercaptoalkanoic acid molecules and metal ions are combined with conventional top-down lithography to create precise, registered nanogaps. However, the quality of the metal-ligated mercaptoalkanoic acid multilayer is a critical characteristic in generating reproducible and robust nanoscale structures via the molecular-ruler process. Therefore, we explore the assembly of alkanethiolate monolayers, mercaptohexadecanoic acid (MHDA) monolayers, and Cu-ligated MHDA multilayers on Au{111} substrates using atomic force microscopy and in situ dynamic spectroscopic ellipsometry. The chemical film thicknesses in situ dynamic spectroscopic ellipsometry agree with previous ex situ surface analytical methods. Moreover, in situ dynamic spectroscopic ellipsometry provides insight into the assembly process without interrupting the assembly process and potentially altering the characteristics of the resulting chemical film. By following the real-time dynamics of each deposition step, the assembly of the Cu-ligated MHDA multilayers can be optimized to minimize deposition time while having minimal impact to the quality of the chemical film.

We report the temperature dependences of the dielectric function ε = ε1 + iε2 and critical point (CP) energies of the uniaxial crystal GaSe in the spectral energy region from 0.74 to 6.42 eV and at temperatures from 27 to 300 K using spectroscopic ellipsometry. The fundamental bandgap and strong exciton effect near 2.1 eV are detected only in the c-direction, which is perpendicular to the cleavage plane of the crystal. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that incorporates the Bose–Einstein statistical factor and the temperature coefficient to describe the electron–phonon interaction. To determine the origin of this anisotropy, we perform first-principles calculations using the mBJ method for bandgap correction. The results clearly demonstrate that the anisotropic dielectric characteristics can be directly attributed to the inherent anisotropy of p orbitals. More specifically, this prominent excitonic feature and fundamental bandgap are derived from the band-to-band transition between s and pz orbitals at the Γ-point.

The optical and surface morphological properties of thin films are profoundly influenced by the deposition technique and the various process parameters employed. In present work, several tantalum penta oxide thin films have been fabricated using reactive electron beam evaporation at varying oxygen (O2) pressures, ranging from 3 × 10−3 Pa to 8 × 10−2 Pa. Refractive index, extinction coefficient, and voids in thin film microstructure were determined through the analysis of spectroscopic ellipsometric measurements. The refractive index, which exhibits a decreasing trend, varies between 1.859 and 2.067, with the exception being the lowest O2 pressure. The variation has been explained in terms of varying oxygen content and voids in the thin films. The extinction coefficient exhibits a decreasing trend due to the increasing oxidation of tantalum, except at O2 pressure of 8 × 10−2 Pa. Increase in the extinction coefficient at this pressure could be due to porous film microstructure, resulting in dominant light scattering. Variation of film density which is similar to that of refractive index, has been attributed to the varying oxidation of tantalum (Ta) and film porosity. Surface root mean square (rms) roughness, correlation length and Hurst parameter, have been derived from suitable analysis of atomic force microscopy measurements. Variations of correlation length and rms roughness have been explained in terms of varying surface shadowing effects and oxidation of Ta with varying O2 pressure.

Eu-doped periodic mesoporous organosilicate (PMO) films with terminal methyl and ethylene bridging groups have been synthesized using sol-gel technology and spin-coating, employing evaporation-induced self-assembly (EISA), on silicon wafers. Eu doping is achieved by the dissolution of Eu(NO3)3·6H2O in the precursor solution. The deposited films are characterized using Fourier transform infrared (FTIR) spectroscopy, ellipsometric porosimetry (EP), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy. It is observed that Eu doping reduces the concentration of terminal methyl groups, makes the films more hydrophilic and reduces the pore size and open porosity. The reduction reaction Eu3+ → Eu2+ occurs in the pores of organosilicate glass (OSG) films, which was confirmed by the depth profiling XPS. Eu3+ was still present on the top surface of the films. The presence of Eu3+ and Eu2+ gives luminescence emission in the range of 600–630 nm (Eu3+) and 290–400 nm (Eu2+). The Eu2+/Eu3+ concentrations ratio depends on CH3 groups concentration in the films. The concentration of Eu2+ ions in the pores can be reduced by exposure to inductively coupled (ICP) oxygen plasma. The observed shift in the luminescence spectra towards the UV region, in comparison to previously reported Eu-doped organosilicate films, can be attributed to the energy transfer occurring between the host material and Eu2+ ions. [ABSTRACT FROM AUTHOR]

Thin HfO2 films atomic layer deposited from hafnium alkyl amide and oxygen plasma were analysed using spectroscopic ellipsometry and X-ray reflectivity. Low refractive index of the material for samples with less than 30 nm thickness marks the index inhomogeneity at the first stage of growth. The transition from rising density to a more stable growth takes place at about 10 to 25 nm film thickness. HfO2 films used for resistive switching experiments demonstrate either clockwise or counterclockwise behaviour depending on the film thickness. The reason for this may be the disruption of the conductive filament at different metal-insulator interfaces, which could be favoured by several mechanisms. [ABSTRACT FROM AUTHOR]

The impacts of the substrate temperature on diverse microstructural, morphological, and optical features of the nickel oxide films deposited via spray pyrolysis were examined. The X-ray diffraction patterns revealed a dominant peak with (1 1 1) favored orientation for all the deposited samples. As the temperature went up from 350 to 450 °C, the indirect and direct band gap energies increased between 2.65 and 2.77 eV and from 3.80 to 3.89 eV, respectively. The thickness and the optical constants of the nickel oxide were estimated by fitting the measured Psi and Delta parameters by adopting a suitable optical model based on B-splines in the wavelength range of 380–900 nm. We obtained that the refractive index significantly decreased from 1.717 to 1.59. But, the extinction coefficient substantially augmented from 0.383 to 0.515. Furthermore, the values of the average oscillator and the dispersion energies were estimated by utilizing the Wemple-DiDomento model. At last, there was a correlation between the different sizes of the crystallite and the optical parameters of the nickel oxide thin films. The optical band gap increased while the refractive index and Urbach energy reduced with a rise in crystallite size. [ABSTRACT FROM AUTHOR]

The residual impurities in chemical vapor deposition (CVD)‐grown hexagonal boron nitride (h‐BN) on Al2O3 substrate grown by CVD using BN‐molded susceptor with B2H6 as a boron precursor are investigated. The Si, C, and O residual impurities of 2.6 × 1016, 3.4 × 1018, and 2.0 × 1017 cm−3 are achieved. These concentrations are two orders of magnitude lower than those when grown on the SiC‐coated graphite susceptor using trimethylboron (TMB) and the lowest values in the CVD‐grown h‐BN thin films. The cathodoluminescence spectrum has 5.5 eV as a broad peak and 4 eV as several peaks. The free excitonic recombination at the higher energy emission (5.79 eV) is owing to the reduction in residual impurities. The absorption coefficient of 1 × 104 cm−1 is observed in the energy range below 5 eV only when using the SiC‐coated graphite susceptor, which is most probably associated with Si contamination in the BN layer. The negligible absorption coefficient when using the BN‐molded susceptor presents high‐purity h‐BN signature. [ABSTRACT FROM AUTHOR]