Ultraviolet Optical Properties Research Articles

Two Noncentrosymmetric Bismuth Phosphates: Rational Design Synthesis and Optical Properties.

Developing strategies to rational design noncentrosymmetric structure still attract much interest for their applications in nonlinear optical and piezoelectric materials. Two noncentrosymmetric (NCS) alkaline earth metal bismuth phosphates have been successfully achieved via partial replacement of Bi3+ with Ca2+ or Sr2+ ions. BiCa(H0.5PO4)2 (designated as CaBiPO) and BiSr(H0.5PO4)2 (designated as SrBiPO), together with their solid solution Bi(Sr1-xCax)(H0.5PO4)2 (0 < x ≤ 0.5), crystallize in the NCS space group C2. Both CaBiPO and SrBiPO exhibit ultraviolet nonlinear optical (NLO) properties, and their second-harmonic generation effects belong to type-II phase matching. Meanwhile, they could also act as photoluminescence hosts in which the Eu3+-doping samples SrBiPO:xEu3+ (x = 0.02-0.2) emit orange light. The effect of different radius ions on the derivative structures and the structure-NLO property relationship has also been discussed in detail.

Band gap energy and near infrared to ultraviolet complex optical properties of single crystal TbScO3

TbScO3 is a wide bandgap semiconductor with potential applications in charge trap memory devices and acts as an alternate gate dielectric in fully depleted transistors and also a substrate for epitaxial thin film growth. TbScO3 has an orthorhombic crystal structure, which gives rise to optical anisotropy. Generalized ellipsometric spectra are measured for multiple in-plane rotations of (110) and (001) oriented TbScO3 single crystals over a photon energy range of 0.7–8.5 eV to determine the complex dielectric function (ε = ε1 + iε2) spectra for electric fields oscillating along each axis. A direct bandgap is identified at 6.50 eV, and above gap critical point transitions are found at 6.99, 7.14, 7.16, 7.21, and 7.42 eV.

Ultraviolet Filters for Cosmetic Applications

Sunscreens reduce the occurrence risk of skin disorders such as sunburn, skin aging, and cancer through their ability to absorb, reflect, and scatter ultraviolet (UV) radiation. This review provides an overview of UV filters as active ingredients of sunscreen products, emphasizing their classification and structural characteristics. Their photostability, mechanism of action of ultraviolet radiation absorption, optical properties, and regulatory status are discussed based on their chemical structure. The main classes of organic UV filters presented include aminobenzoic acid derivatives, salicylic acid derivatives, cinnamic acid derivatives, benzophenones, dibenzoylmethane derivatives, benzylidene camphor derivatives, triazines, benzimidazole derivatives, and benzotriazole derivatives. The pursuit of new UV filters through research is crucial in advancing sunscreen technology and ensuring the availability of effective and safe options for sun protection.

Chiral helicene nanohoop in One- and Two-photon absorption and ECD spectra

The optical and spectral properties of helicene carbon nanoloops with Mobius topology are of great importance in nanoscience and nanotechnology. There are potential applications prospects in many fields. We theoretically investigate the ultraviolet optical properties of Möbius topological helicene carbon nanoloop by density of states, photoelectronic spectrum, the Independent gradient model, charge transfer spectrum and Electronic circular dichroism. This reveals a unique characterization of carbon nanoops using Mobius topology. Our results can not only provide insights into the physical mechanism of optical absorption of Mobius topological helicene carbon nanoloop, but also provide suggestions for potential applications of Mobius topological helicene carbon nanoloop in optical nanodevices.

Vacuum ultraviolet optical properties of GaSb determined by synchrotron rotating analyzer ellipsometry: applications in nanopillars and plasmonics

The vacuum ultraviolet (VUV) optical properties in the range 4 eV to 15 eV of GaSb have been determined by rotating analyzer ellipsometry (RAE) using synchrotron light. The localized surface plasmon resonances (LSPRs) and surface plasmon polaritons (SPPs) are studied as a means to understand the plasmonic behavior of GaSb. The large imaginary part of the dielectric function causes poor confinement of the SPP. Self-assembled GaSb nanopillars of 35 nm height are studied experimentally by RAE at different angles of incidence. The pillars are simulated numerically using an effective medium approach and the finite element method (FEM), where clear similarities between the simulations and experiment are observed. Additional dips in the reflectivity accompanied by increased nanopillar absorption and local field enhancement were observed near the surface of the pillars. These results demonstrate GaSb nanopillars to be promising candidates for photocathodes.

Depth-resolved photochemical production of hydrogen peroxide in the global ocean using remotely sensed ocean color

Hydrogen peroxide (H2O2) is an important reactive oxygen species (ROS) in natural waters, affecting water quality via participation in metal redox reactions and causing oxidative stress for marine ecosystems. While attempts have been made to better understand H2O2 dynamics in the global ocean, the relative importance of various H2O2 sources and losses remains uncertain. Our model improves previous estimates of photochemical H2O2 production rates by using remotely sensed ocean color to characterize the ultraviolet (UV) radiation field in surface water along with quantitative chemical data for the photochemical efficiency of H2O2 formation. Wavelength- and temperature-dependent efficiency (i.e., apparent quantum yield, AQY) spectra previously reported for a variety of seawater sources, including coastal and oligotrophic stations in Antarctica, the Pacific Ocean at Station ALOHA, the Gulf of Mexico, and several sites along the eastern coast of the United States were compiled to obtain a “marine-average” AQY spectrum. To evaluate our predictions of H2O2 photoproduction in surface waters using this single AQY spectrum, we compared modeled rates to new measured rates from Gulf Stream, coastal, and nearshore river-outflow stations in the South Atlantic Bight, GA, United States; obtaining comparative differences of 33% or less. In our global model, the “marine-average” AQY spectrum was used with modeled solar irradiance, together with satellite-derived surface seawater temperature and UV optical properties, including diffuse attenuation coefficients and dissolved organic matter absorption coefficients estimated with remote sensing-based algorithms. The final product of the model, a monthly climatology of depth-resolved H2O2 photoproduction rates in the surface mixed layer, is reported for the first time and provides an integrated global estimate of ∼21.1 Tmol yr−1 for photochemical H2O2 production. This work has important implications for photo-redox reactions in seawater and improves our understanding of the role of solar irradiation on ROS cycling and the overall oxidation state in the oceans.

Designing of Praseodymium Oxide Nanoparticle-Based Photoluminescent Composite Films Using Polyurethane Matrix

Abstract Praseodymium oxide nanoparticle-embedded composite films were prepared using praseodymium nitrate and transparent urethane resin. The prepared films were further irradiated with ultraviolet (UV) light, and subsequently, their microstructure and optical properties were investigated. The color of the composite films turned from pale green (close to the precursor color) to reddish brown owing to UV irradiation. Pr6O11 particles were found to be present in the obtained films, and the particle size in the films increased upon increasing the UV irradiation time. The films obtained after UV irradiation showed absorption peaks at 444, 468, 483, 592, and 1020 nm, which were attributed to 3H4→3P2, 3P1, 3P0, 1D2, and 1G4, respectively, corresponding to the 4f-4f transition of Pr3+. The composite films exhibited photoluminescence with a peak at 605 nm corresponding to the 1D2→3H4 transition of Pr3+ up on excitation with 444 nm light.

Na3B6O10(HCOO): an ultraviolet nonlinear optical sodium borate-formate

A new sodium borate-formate, which displays a pcu-type open framework and ultraviolet nonlinear optical properties, has been synthesized under surfactant-thermal conditions.

Effects of phase transformation on the ultraviolet optical properties of alumina clusters in aircraft plumes.

Alumina particles experience phase transition as an undercooling process along the plume, during which the liquid alumina clusters transform into multiphase, and then into α phase. The phase transformation model was built by an improved diffusion limited aggregation (DLA) algorithm with monomers of stratified structure. The effects of phase transformation on the ultraviolet optical characteristics of alumina clusters were studied using the superposition T-matrix method (STMM). We found that the alumina clusters in phase transition had completely different optical properties compared with the fixed phase ones. Forward scattering, absorption efficiency and asymmetry parameter gradually decreased, whereas backward scattering, scattering efficiency, and single-scattering albedo gradually increased during the phase transformation process. Besides, multiphase alumina clusters were compared with the other two equivalent models, including the sphere model approximated by equivalent volume sphere (EVS) and the equivalent surface sphere (ESS) approaches and single-phase cluster model approximated by Maxwell-Garnett (MG) and Bruggeman (BR) approaches. Generally speaking, the optical properties of the single-phase cluster approximated by MG and BR approaches were relatively close to those of the real multiphase alumina cluster. Whereas the spheres approximated by EVS and ESS had great deviations, especially when the number of monomers in the cluster was 20, the relative error of scattering efficiency calculated by ESS was up to 52%. Therefore, approximate approaches for multiphase clusters should be chosen cautiously. Our results give further the understanding of the optical properties of alumina clusters. As the phase states are usually closely related to the plume radiation and burning process, these kinds of researches will be helpful to aircraft detection, identification, and other related fields.

First-principle study on structural, linear and nonlinear optical properties of selenocyanate complex ZnCd(SeCN)4 crystal

Bimetallic selenocyanate complex ZnCd(SeCN)4 (ZCSC) crystals are a novel material with ultraviolet nonlinear optical (NLO) properties. To the best of our knowledge, theoretical studies on these complexes have mostly focused on the microcosmic NLO responses of single complex molecular system and ignored their macroscopic NLO effects. In this paper, the geometric structure of ZCSC crystal was optimized on the basis of first principle, and the electronic band structure and linear optical (LO) properties were investigated via pseudopotential plane wave method. The macroscopic NLO properties of ZCSC crystal were evaluated through the combination of density functional theory and a devised anionic group method for the first time, and good agreement with the experimental results was obtained. The absorption spectrum of ZCSC was located at 95–325 nm, and the NLO properties were mainly caused by the transitions of electronic states from N2p and Se3p valence bands to C2p, N2p, Se3p, and Cd4p conduction bands. Results showed that the second-order NLO coefficients were d14 = 2.304–3.55 pm/V and d15 = 8.07–9.91 pm/V, showing an evident increase compared with those of ZnCd(SCN)4 crystals.

Ultraviolet optical properties and structural characteristics of radio frequency-deposited HfO2 thin films

Hafnium oxide (HfO $_2$ ) thin films were deposited on quartz substrate by radio frequency magnetron sputtering with power from 160 W to 240 W. The optical and microstructural properties of samples before and after annealing were characterized by XRD, XPS, UV-VIS-NIR spectrophotometer and ellipsometer. The results show optical transmittances with low absorption in wavelength range above $\lambda$ =200 nm for all samples. The appropriate annealing can transfer the amorphous state of as-deposited films to the crystal film, contribute to the growth of nanocrystalline and compressive stress, optimize the stoichiometry of the film and systematically improve film density and the refractive index. In consideration of the stability of proper refractive index (> 2) and high optical transmittance in UV band, HfO $_2$ films deposited approximately at 220 W can be used in UV anti-reflection system.

Ultraviolet optical properties of ZnS quantum-dots synthesized in ethanol

We investigated the UV optical properties of 2.2 to 2.5 nm colloidal ZnS quantum dots (QDs) that were synthesized using a one-step solution-processed method. X-ray diffraction patterns and transmission electron microscopy images show clear cubic zinc-blende ZnS structure. Photoluminescence results show defect-related light emission with a peak wavelength that can be tuned from 400 to 389 nm by changing the particle size of the ZnS QDs. As judged from absorption spectroscopy, the optical bandgaps of the QD suspensions then change from 4.0 to 4.2 eV and for the QD films from 3.9 to 4.0 eV, showing clear quantum confinement. The excitation spectra show excitation maxima at the exciton energy, changing from 3.89 eV (319 nm) down to 4.07 eV (305 nm).

Free-standing coating patterns fabricated by ultraviolet contact lithography using photosensitive sol-gel coatings

Photosensitive ZrO2-SiO2 hybrid sol-gel coatings containing large contents of chelating rings were prepared by using the zirconium n-butoxide (TBOZ) and methyltriethoxysilane (MTES) as hybrid precursors, and benzoylacetone (BZAC) as chelating agent. The change of ultraviolet (UV) absorption spectra, chemical composition, and optical properties of ZrO2-SiO2 hybrid sol-gel coatings were analyzed before and after UV exposure and calcination. The refractive index of the ZrO2-SiO2 hybrid gel coatings decreased from 1.673 to 1.561 with the increase of the molar content of MTES in precursors. The sol-gel coating patterns with the periods of 20.24 μm, 10.11 μm and 3.99 μm on the PAMS substrates were firstly obtained by using the photosensitive ZrO2-SiO2 hybrid sol-gel films as fundamental materials through a process of UV contact lithography with photo masks and etching with ethanol. Finally, the free-standing gel coating patterns supported by copper grids, with the period of 12.70 μm and line width of 4.93 μm, and the period of 14.20 μm and line width of 3.82 μm, were obtained by removing the PAMS thermal degradation sacrifice layer after being calcined at 330 °C. Micrometer-periodic free-standing gel coating patterns with different structure have potential applications in the laser physical experiments.

Near infrared to ultraviolet anisotropic optical properties of single crystal SrLaAlO4 from spectroscopic ellipsometry

The anisotropic optical properties of single crystal SrLaAlO4 are investigated using spectroscopic ellipsometry over the range from 0.74 to 5.90 eV. Divided spectral range analysis of ellipsometric and Mueller matrix spectra are used to obtain the sample structural parameters (surface roughness thickness and void fraction). The ordinary and extra‐ordinary optical properties in the form of complex dielectric function, ϵ = ϵ1 + iϵ2 (or complex index of refraction, N = n + ik), spectra are extracted from the same analysis. The observed birefringence is ∼ 0.025 in the transparent range. An upper limit for the indirect gap at 3.01 ± 0.01 eV and a critical point at 5.54 ± 0.01 eV are identified within the measured spectral range.

Near infrared to ultraviolet optical properties of bulk single crystal and nanocrystal thin film iron pyrite

We report optical properties of iron pyrite (FeS2) determined from ex situ spectroscopic ellipsometry measurements made on both a commercially available bulk single crystal and nanocrystalline thin film over a spectral range of 0.735–5.887 eV. The complex dielectric function, ε (E) = ε1 (E) + iε2 (E), spectra have been determined by fitting a layered parametric model to the ellipsometric measurements. Spectra in ε are modeled using a Kramers–Kronig consistent critical point parabolic band model involving seven critical points for the bulk single crystal and four critical points for the nanocrystalline film. Absorption coefficient spectra for both types of samples are also determined from ε. Critical point features in the nanocrystalline films are broader, have lower amplitude and lower energy critical points detected having a small blue shift when compared to the single crystal sample.

Ultraviolet optical properties of aluminum fluoride thin films deposited by atomic layer deposition

Aluminum fluoride (AlF3) is a low refractive index material with promising optical applications for ultraviolet (UV) wavelengths. An atomic layer deposition process using trimethylaluminum and anhydrous hydrogen fluoride has been developed for the deposition of AlF3 at substrate temperatures between 100 and 200 °C. This low temperature process has resulted in thin films with UV-optical properties that have been characterized by ellipsometric and reflection/transmission measurements at wavelengths down to 200 nm. The optical loss for 93 nm thick films deposited at 100 °C was measured to be less than 0.2% from visible wavelengths down to 200 nm, and additional microstructural characterization demonstrates that the films are amorphous with moderate tensile stress of 42–105 MPa as deposited on silicon substrates. X-ray photoelectron spectroscopy analysis shows no signature of residual aluminum oxide components making these films good candidates for a variety of applications at even shorter UV wavelengths.

Mid-infrared to ultraviolet optical properties of InSb grown on GaAs by molecular beam epitaxy

Spectroscopic ellipsometry was used to investigate the optical properties of an InSb film grown on a GaAs (100) substrate, and to compare the optical properties of InSb film with those of bulk InSb. The film was grown by molecular beam epitaxy under conditions intended to form 90° misfit dislocations at the InSb-GaAs interface. The complex dielectric function obtained in a wide spectroscopic range from 0.06–4.6 eV shows the critical point transitions E0, E1, E1 + Δ1, E0′, and E2. The amplitudes, energy transitions, broadenings, and phase angles have been determined using a derivative analysis. Comparing film and bulk critical point results reveal that the epitaxial film is nearly relaxed and has bulk-like optical characteristics.

Size-Controlled Synthesis of Bifunctional Magnetic and Ultraviolet Optical Rock-Salt MnS Nanocube Superlattices

Wide-band-gap rock-salt (RS) MnS nanocubes were synthesized by the one-pot solvent thermal approach. The edge length of the nanocubes can be easily controlled by prolonging the reaction time (or aging time). We systematically explored the formation of RS-MnS nanocubes and found that the present synthetic method is virtually a combination of oriented aggregation and intraparticle ripening processes. Furthermore, these RS-MnS nanocubes could spontaneously assemble into ordered superlattices via the natural cooling process. The optical and magnetic properties were investigated using measured by UV-vis absorption, photoluminescence spectra, and a magnetometer. The obtained RS-MnS nanocubes exhibit good ultraviolet optical properties depending on the size of the samples. The magnetic measurements suggest that RS-MnS nanocubes consist of an antiferromagnetic core and a ferromagnetic shell below the blocking temperatures. Furthermore, the hysteresis measurements indicate these RS-MnS nanocubes have large coercive fields (e.g., 1265 Oe for 40 nm nanocubes), which is attributed to the size and self-assembly of the samples.

Optical properties of super stoichiometric TiN1 + x thin films

Nitrogen-rich titanium nitride (TiN1+x) thin films containing between 70.4at.% and 87.0at.% nitrogen were synthesized and deposited onto single crystal silicon with a (100) crystallographic orientation via the reactive magnetron direct current (DC)-sputtering by systematically varying the process pressure and substrate temperature. The ultraviolet and visible optical properties of these chemically unique TiN1+x thin films have been explored vs. surface roughness and stoichiometry. The specular and diffuse reflectances are linearly coupled to the root mean square surface roughness. The reflectance and absorption were shown to be wavelength dependent. Absorption coefficients for these non-transparent thin films were experimentally determined by monitoring the real-time transient temperature profile of the films and directly correlating the maximum temperature increment to the linear absorption coefficient. The linear absorption coefficient was found to range between 9.11×105 and 3.84×106cm−1 and is strongly coupled to the incident wavelength and nitrogen content. The interaction depths range between 2 and 11nm, indicating interaction only near the film surface.

Double slit interferometry to measure the EUV refractive indices of solids using high harmonics

Accurate values of the extreme ultraviolet (EUV) optical properties of materials are required to make EUV optics such as filters and multilayer mirrors. The optical properties of aluminum studied in this report are required, in particular, as aluminum is used as an EUV filter material. The complex refractive index of solid aluminum and the imaginary part of the refractive index of solid iron between 17 eV and 39 eV have been measured using EUV harmonics produced from an 800 nm laser focused to 10(14) Wcm(2) in an argon gas jet impinging on a double slit interferometer.