Optical Properties Of Materials Research Articles

Optical Properties of Materials for Magnesium Plasmonics Described within DFT+U Approach

Optical Properties of Materials for Magnesium Plasmonics Described within DFT+U Approach

2D Materials for Photothermoelectric Detectors: Mechanisms, Materials, and Devices

Abstract2D materials, with outstanding optical, thermal, and electric properties, are emerging as promising candidates for fabricating high‐performance photodetectors. Recently, impressive progresses have been made in this area and some challenges are remaining to improve the properties of photodetectors. As one important part in the mainstream photodetection mechanisms, photothermoelectric (PTE) effect is showing unique priorities in fabricating advanced photodetectors, especially broadband detection operating in the mid‐infrared and terahertz spectral regime. Here, recent progress on PTE photodetectors based on layered 2D materials is reviewed. The physical mechanism of PTE effect is first discussed and then the optical and thermoelectric properties of various 2D materials are analyzed. Furthermore, strategies to improve the photodetection performance of PTE detectors are summarized in two major categories including enhanced photothermal conversion and thermoelectric conversion processes. Finally, the challenges and prospects for future research in 2D thermoelectric materials and PTE detectors are also provided.

Designing and Tailoring Optical Properties: Theory and Simulation of Photonic Band Gaps in Photonic Materials

Theoretical calculations and numerical simulations play a crucial role in analyzing material properties and devising effective research strategies. In this study, the photonic band gap (PBG) of polymethyl methacrylate (PMMA) and polystyrene (PS) photonic crystals was successfully predicted using theoretical calculations and numerical simulations. The agreement between the predicted results and the actual reflection peaks reached an impressive level of 99%. Utilizing SEM images, the prediction of reflection peaks in acrylamide (AM)—based photonic hydrogels was conducted using theoretical formulas and Rsoft 2019–Bandsolve software v2019.09. The relationship between the actual reflection peaks and compressive strains in AM-based photonic hydrogels featuring 251 nm PMMA PCs exhibited a remarkable similarity of over 96% with the theoretical and simulated results. In conclusion, an exploration was conducted into the relationship between reflection peaks and compressive strains for AM-based 270 nm PMMA photonic hydrogels, allowing the prediction of the actual reflection peaks under compression. The consistency observed between theoretical/simulated reflection peaks and actual reflection peaks validates the efficacy of this approach in evaluating the optical properties of photonic materials and predicting their responsive effects. This method offers a straightforward and expeditious solution for the design and fabrication of photonic materials.

Nanomaterials Based Micro/Nanoelectromechanical System (MEMS and NEMS) Devices.

The micro- and nanoelectromechanical system (MEMS and NEMS) devices based on two-dimensional (2D) materials reveal novel functionalities and higher sensitivity compared to their silicon-base counterparts. Unique properties of 2D materials boost the demand for 2D material-based nanoelectromechanical devices and sensing. During the last decades, using suspended 2D membranes integrated with MEMS and NEMS emerged high-performance sensitivities in mass and gas sensors, accelerometers, pressure sensors, and microphones. Actively sensing minute changes in the surrounding environment is provided by means of MEMS/NEMS sensors, such as sensing in passive modes of small changes in momentum, temperature, and strain. In this review, we discuss the materials preparation methods, electronic, optical, and mechanical properties of 2D materials used in NEMS and MEMS devices, fabrication routes besides device operation principles.

Effect of vacuum sintering on the microstructure and spectroscopic properties of Eu doped strontium titanate ceramics

In this work, we report on the optical properties of europium-doped SrTiO3, synthesized in situ via the sol-gel method as nanopowders and sintered ceramic bulks by heat treatment in vacuum. The structure and morphology of the Sr1-3x/2EuxTiO3 (x = 0.01–0.07) nanopowders and ceramics, concerning to the europium concentration, were characterized by X-ray powder diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The optical properties of as-prepared materials were also investigated. These analyses demonstrated that a temperature of 1425 °C in a vacuum of 10−4 Pa and a plateau of 4h are the optimal sintering conditions for Sr1-3x/2EuxTiO3 ceramics. Eu3+ doped SrTiO3 ceramics exhibit visible red photoluminescence characteristics. The emission of SrTiO3:Eu3+ phosphor with different amounts of Eu3+, excited by 395 nm and 465 nm light, was studied. The emission spectra exhibit characteristic luminescence from 5D0 → 7Fj (j = 0, 1, 2, 3, 4) intra-4f shell Eu3+ ion transitions. The most intense transitions are 5D0 → 7F1 (591 nm) for pumping at 395 nm and, 5D0 → 7F2 (615 nm) at 465 nm. The corresponding coordinates CIE for the Eu-doped SrTiO3 samples were calculated from the emission spectra obtained at 395 nm and 465 nm excitation wavelengths. This study demonstrates that the original protocol of materials engineering used is a simple and efficient method for manufacturing novel nanophosphors with enhanced reddish-orange emission. The as-obtained results indicated that the sol-gel synthesis combined with the sintering process in a vacuum at an appropriate temperature, plateau, could be a novel way to fabricate materials based on strontium titanate with reasonable optical properties.

Optical transition tuning of Er3+ in continuous tungsto-molybdate solid solution NaY(MoxW1-xO4)2 phosphors

Nowadays, the application scenarios of rare earth doped luminescent materials tend to be refined and complicated. The optical properties of rare earth doped materials are difficult to precisely control via the traditional design and synthesis methods, namely, changing doping concentration or preparative conditions. The aim of this study is to tune the optical transition properties of Er3+ in tungsto-molybdate NaY(MoxW1-xO4)2 (x = 0, 0.01, 0.1, 0.3, 0.5, 0.7, 0.9, 0.99 and 1.0) phosphors by changing the host matrix. The Er3+ doped continuous tungsto-molybdate solid solution NaY(MoxW1-xO4)2 phosphors were prepared via a solid state reaction technique at optimized calcination temperatures. The refractive indexes of the obtained solid solution samples were confirmed according to different models and compared. Subsequently, the optical transition intensity parameters, radiative transition rates and intrinsic radiative lifetimes of Er3+ in these solid solution phosphors were calculated in the framework of Judd-Ofelt theory. It was confirmed that the optical transition properties of Er3+ can be greatly tuned by the solid solution composition, and the tuning effects for different transitions are different. To validate the reliability of the Judd-Ofelt calculations, the temperature-dependent emission spectra of two green emissions of Er3+ for different solid solution samples were studied. It was found that the radiative transition rate ratios between two green emissions derived from theoretical calculations and experimental measurements are in reasonable agreement, thus proving that the optical transition calculations are reliable and the optical transition properties of Er3+ in the tungsto-molybdates can be tuned in a large range. This work reminds us of a new route for developing novel luminescence materials based on practical demands.

Structural, optical and magnetic properties of Fe, Co and Co[sbnd]Fe doped SnO2 thin films deposited by a thermionic vacuum arc deposition system

Fe, Co and CoFe doped SnO2 thin films were deposited onto glass, indium tin oxide-coated glass, and Si substrates to investigate the influence of substrate material on the surface and magnetic properties. The motivation of this study is to investigate the magnetic, surface, and optical properties of doped SnO2 semiconductor materials as they vary with different substrate materials. The film surfaces are smooth and compact. Additionally, nano particles were observed. Thin films of SnO2 doped with Fe, Co and CoFe doped SnO2 have a Curie temperature. Magnetization–temperature and magnetization–temperature graphs have shown the predicted magnetic properties. These films have giant magnetization and soft magnetic properties. In separately doped Fe and Co – SnO2 thin films, the M (emu) values are nearly the same. In Co and Fe-doped SnO2 thin films, the M (emu) values for the film deposited onto ITO-coated glass and uncoated glass are nearly the same.

Strong Exciton-Phonon Coupling as a Fingerprint of Magnetic Ordering in van der Waals Layered CrSBr.

The layered, air-stable van der Waals antiferromagnetic compound CrSBr exhibits pronounced coupling among its optical, electronic, and magnetic properties. As an example, exciton dynamics can be significantly influenced by lattice vibrations through exciton-phonon coupling. Using low-temperature photoluminescence spectroscopy, we demonstrate the effective coupling between excitons and phonons in nanometer-thick CrSBr. By careful analysis, we identify that the satellite peaks predominantly arise from the interaction between the exciton and an optical phonon with a frequency of 118 cm-1 (∼14.6 meV) due to the out-of-plane vibration of Br atoms. Power-dependent and temperature-dependent photoluminescence measurements support exciton-phonon coupling and indicate a coupling between magnetic and optical properties, suggesting the possibility of carrier localization in the material. The presence of strong coupling between the exciton and the lattice may have important implications for the design of light-matter interactions in magnetic semiconductors and provide insights into the exciton dynamics in CrSBr. This highlights the potential for exploiting exciton-phonon coupling to control the optical properties of layered antiferromagnetic materials.

Thin films with implemented molecular switches for the application in polymer-based optical waveguides

Complexes like iron (II)-triazoles exhibit spin crossover behavior at ambient temperature and are often considered for possible application. In previous studies, we implemented complexes of this type into polymer nanofibers and first polymer-based optical waveguide sensor systems. In our current study, we synthesized complexes of this type, implemented them into polymers and obtained composites through drop casting and doctor blading. We present that a certain combination of polymer and complex can lead to composites with high potential for optical devices. For this purpose, we used two different complexes [Fe(atrz)3](2ns)2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$[\ ext {Fe}(\ ext {atrz})_{3}](2\\, \ ext {ns})2$$\\end{document} and [Fe(atrz)3]Cl1.5(BF4)0.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$[\ ext {Fe}(\ ext {atrz})_{3}]\ ext {Cl}_{1.5}(\ ext {BF}_{4})_{0.5}$$\\end{document} with different polymers for each composite. We show through transmission measurements and UV/VIS spectroscopy that the optical properties of these composite materials can reversibly change due to the spin crossover effect.

Preparation of fullerene-containing nanocomposite materials based on high-density polyethylene via environmental crazing and their performance

This work offers a new concept relying on the Rehbinder effect in polymers for the preparation of fullerene-containing nanocomposite materials with added functionality. Tensile drawing of high-density polyethylene (HDPE) films in the solutions of 1,2–dichlorobenzene containing С60-С70 fullerenes (FL) proceeds via the environmental crazing according in the presence of surface active liquids (the Rehbinder effect). Environmental crazing provides the development of a highly developed surface and a mesoporous structure with a uniform distribution of monomeric FL within the HDPE matrix. The content of FL in the FL/HDPE nanocomposite materials can be varied from 1 to 8 wt%. Performance of the FL/HDPE nanocomposite materials (optical properties, thermal stability, mechanical characteristics) was studied by different physicochemical methods (TGA, UV- spectroscopy, tensile tests, etc.). Introduction of FL to HDPE is shown to increase the temperature of thermal degradation onset of HDPE by 30 °C. Rolling as the additional stage off post-treatment allows preparation of the FL/HDPE nanocomposite materials with high mechanical properties. This process can be upscaled using the existing technological equipment for the orientational drawing of polymers. The FL/HDPE nanocomposites with improved thermal resistance and good mechanical properties can be used as innovative optoelectronic materials within a broad temperature interval.

Multi‐Color Magnetic Circularly Polarized Luminescence from Achiral Perovskite (Cs+Pb2+X3) Quantum Dots

AbstractHigh‐performance optoelectronic materials require luminescent materials capable of intense photoluminescence (PL). However, controlling the optical properties of luminescent materials requires complex synthesis and purification procedures. Herein, we propose a simple method for obtaining circularly polarized luminescence from achiral inorganic quantum dots. This method involves applying north‐up and south‐up 1.7 T magnetic fields at 25 °C to five types of achiral antimagnetic perovskite‐Pb‐quantum dots in a solution state. The wavelengths of magnetic circularly polarized luminescence (MCPL) and PL of achiral perovskite‐Pb quantum dots were successfully controlled according to the type and composition ratio of halogen ions. The magnitude of MCPL, gMCPL, was on the order of |gMCPL|=10−3 in a wavelength range of 406–697 nm. Although the perovskite‐Pb‐quantum dots were achiral, the rotation direction of the MCPL could be controlled by varying the direction of the applied magnetic field.

First-principles calculations to investigate structural, electronic, and optical properties of AgWO4 and PdWO4 tungstate materials for optoelectronic applications

The optoelectronic devices play a crucial role in our daily lives by seamlessly integrating optics and electronics, enabling technologies like smartphones, solar cells, and optical communication. Solar cells have been very vital in terms of providing sustainable and clean energy. Conventional Perovskite-based solar cells possess limitations like stability and toxicity. Recently, ABO4-type materials have gained attention in optoelectronic devices due to their structural stability and suitable optoelectronic properties for solar cell applications. The structural, electronic, and optical properties of AgWO4 and PdWO4 have been explored using the first principal simulations in line with density functional theory (DFT) using WIEN2K simulation software. The Perdew-Burke-Ernzerhof Generalized-Gradient-Approximation (PBE-GGA) is acclimated to optimize the geometry of both materials under consideration. Trans-Balha modified Becke-Johnson approximation (TB-mBJ) approximation is implemented to study materials' optoelectronic properties. Structural analysis revealed the stable structure of AgWO4 and PdWO4 in the monoclinic phase with increasing lattice parameters and decreased unit cell volume upon replacement of Ag with Pd cation on the A site. Both materials ' negative values of ground state energies indicate the stability of both compounds. Upon analysis of the band structure of AgWO4 and PdWO4, it is found that both materials possess a band gap of 1.34eV and 0.73eV,respectively, signifying that both materials under consideration are semiconductors, with a potential for a controlled flow of electrical charges, coming up with promising various optoelectronic applications. Optical characteristics were explored and examined in depth in the framework of hypothetical dielectric constant. It has been discovered that the dielectric function has a broad span of energy integrity when it comes to its dielectric function. Materials with narrow bandgaps and excellent UV light absorption were found suitable for optoelectronic and solar cell applications.

Modulating opto‐electronic and magnetic responses of Mo‐ and Zn‐adsorbed LiNbO3 (1 1 1) surface for advanced energy harvesting applications: A comprehensive study

AbstractThis study aimed to comprehensively investigate the optoelectronic and magnetic properties of Mo, Zn/LiNbO3 (1 1 1) material. The primary objectives were to understand the potential for manipulating the material's magnetism and to elucidate the origin of spin‐polarized states and magnetic moments, particularly with respect to the unpaired d orbitals of Nb, Mo, and Zn atoms. To achieve these objectives, we employed the Pardew–Burke–Ernzerhof (PBE) method within the Generalized Gradient Approximation (GGA + U) framework. This computational approach allowed us to examine the optoelectronic and magnetic characteristics of the material in detail. Our research yielded several key findings that enhance our understanding of Mo, Zn/LiNbO3 (1 1 1) material. We observed a modest improvement in the material's absorption capacity within the visible spectrum, accompanied by a discernible red‐shift. Notably, our study involved the calculation of the dielectric function and refractive constant of the material, revealing a strong correlation between absorption trends and the dielectric constant. Furthermore, our investigation uncovered that Mo, Zn/LiNbO3 (1 1 1) exhibits distinct conduction and valence bands, with p and d orbitals predominantly contributing to each, respectively. The energy gap of the material falls within a range of 0.30–1.04 eV. A particularly significant finding was the narrower band gap of Mo, Zn/LiNbO3 (1 1 1) material, which can be attributed to the superposition of Mo‐d and Zn‐p orbit energy levels with O‐p orbit energy levels, ultimately forming a covalent bond. Importantly, our research demonstrated the material's heightened optical absorption within the visible spectrum, suggesting its suitability for various photonic and optoelectronic applications. Additionally, we calculated a wide range of optical characteristics, including the dielectric function, absorption coefficient, energy loss, reflectivity, refractive index, extinction coefficient, and optical conductivity, providing a comprehensive assessment of the material's optical properties.

Electronic and optical properties of Cr / Cl co-doped in single-layer MoS2: A first principles study

This study aims to investigate the co-doping effect of Cr and Cl in monolayer molybdenum disulfide (MoS2) crystals. Density functional theory (DFT) was used to study the electronic structure and optical properties of the doped material, employing the PBE-GGA calculation method for the exchange-correlation energy. Key factors such as density of states, band structure, dielectric function, photoconductivity, refractive index, and absorptivity were analyzed. The findings indicate that co-doping of Cr and Cl reduces the band gap and introduces impurity energy levels within the band gap, thereby improving the photocatalytic performance.

Switchable Optical Properties of Dyes and Nanoparticles in Electrowetting Devices.

The optical properties of light-absorbing materials in optical shutter devices are critical to the use of such platforms for optical applications. We demonstrate switchable optical properties of dyes and nanoparticles in liquid-based electrowetting-on-dielectric (EWOD) devices. Our work uses narrow-band-absorbing dyes and nanoparticles, which are appealing for spectral-filtering applications targeting specific wavelengths while maintaining device transparency at other wavelengths. Low-voltage actuation of boron dipyromethene (BODIPY) dyes and nanoparticles (Ag and CdSe) was demonstrated without degradation of the light-absorbing materials. Three BODIPY dyes were used, namely Abs 503 nm, 535 nm and 560 nm for dye 1 (BODIPY-core), 2 (I2BODIPY) and 3 (BODIPY-TMS), respectively. Reversible and low-voltage (≤20 V) switching of dye optical properties was observed as a function of device pixel dimensions (300 × 900, 200 × 600 and 150 × 450 µm). Low-voltage and reversible switching was also demonstrated for plasmonic and semiconductor nanoparticles, such as CdSe nanotetrapods (abs 508 nm), CdSe nanoplatelets (Abs 461 and 432 nm) and Ag nanoparticles (Abs 430 nm). Nanoparticle-based devices showed minimal hysteresis as well as faster relaxation times. The study presented can thus be extended to a variety of nanomaterials and dyes having the desired optical properties.

The Integration of Two-Dimensional Materials and Ferroelectrics for Device Applications.

In recent years, there has been growing interest in functional devices based on two-dimensional (2D) materials, which possess exotic physical properties. With an ultrathin thickness, the optoelectrical and electrical properties of 2D materials can be effectively tuned by an external field, which has stimulated considerable scientific activities. Ferroelectric fields with a nonvolatile and electrically switchable feature have exhibited enormous potential in controlling the electronic and optoelectronic properties of 2D materials, leading to an extremely fertile area of research. Here, we review the 2D materials and relevant devices integrated with ferroelectricity. This review starts to introduce the background about the concerned themes, namely 2D materials and ferroelectrics, and then presents the fundamental mechanisms, tuning strategies, as well as recent progress of the ferroelectric effect on the optical and electrical properties of 2D materials. Subsequently, the latest developments of 2D material-based electronic and optoelectronic devices integrated with ferroelectricity are summarized. Finally, the future outlook and challenges of this exciting field are suggested.

A Review: Principles and Applications of High-Pressure In Situ Time-Resolved Transient Absorption Spectroscopy

Time-resolved transient absorption (TA) spectroscopy measurement technology provides detailed information into the ultrafast dynamics by tracking the transitions and deactivation processes of the excited-state carriers, which holds vast potential for investigating processes related to the luminescence and nonradiative recombination of materials. Pressure is considered a potent tool for tuning the carrier dynamic behaviors. The combination of high-pressure experimental technology and time-resolved TA spectroscopy measurement technology enables researchers to reveal the inherent relation between the structure and optical properties of materials, which is crucial for optimizing material performance and applications in the field of optoelectronics. In this review, the principles and the theoretical foundations of high-pressure time-resolved TA spectroscopy measurement technology will be introduced, and the research advancements in ultrafast dynamics processes of materials under high pressure will be summarized and discussed. In addition, we will expound on the future prospects of time-resolved TA spectroscopy measurement technology to detect the ultrafast dynamic behaviors of materials and complexes under the coregulation of temperature and pressure.

Strain engineering of the mechanical properties of two-dimensional WS2.

Tuning the physical properties of two-dimensional (2D) materials is crucial for their successful integration into advanced applications. While strain engineering demonstrated an efficient means to modulate the electrical and optical properties of 2D materials, tuning their mechanical properties has not been carried out. Here we applied compressive strain through the buckling metrology to 2D tungsten disulfide (WS2), which demonstrated mechanical softening manifested by the reduction of its effective Young's modulus. Raman modes analysis of the strained WS2 also showed strain-dependent vibrational modes softening and revealed its Grüneisen parameter (γ E2g = 0.29) and its shear deformation potential (β E2g = 0.56) - both are similar to the values of other 2D materials. In parallel, we conducted a molecular dynamic simulation that confirmed the validity of continuum mechanics modeling in the nanoscale and revealed that due to sequential atomic-scale buckling events in compressed WS2, it shows a mechanical softening. Therefore, by tuning the mechanical properties of WS2 we shed light on its fundamental physics, thus making it an attractive candidate material for high-end applications, such as tunable sensors and flexible optoelectronic devices.

Development of low-cost, compact chiroptical imaging systems.

Circular dichroism spectroscopy is a key probe of the structural and optical properties of chiral materials, however, commercial circular dichroism spectrometers are large, prohibitively expensive and rarely offer environmental control of the sample under test. Using Fresnel rhombs as inexpensive broadband quarter-wave plates, we demonstrate two novel, low-cost (<£2000) and portable imaging systems controlled by our own bespoke open-source control software which are capable of spatially mapping the circular dichroism of chiral solid state films. By coupling these imaging systems with a temperature controlled stage, we show that we can rapidly identify the thermal processing conditions required to maximise circular dichroism in chiral solid state films by measuring circular dichroism in situ during thermal annealing of a sample under test. The accuracy and spatial resolution of these circular dichroism imagers are cross-compared against our previous studies using an existing circular dichroism imaging system at the Diamond Light Source and are shown to be in good agreement, with a sensitivity down to 250 mdeg and a spatial resolution of 100 μm.

Investigation of granular natural stone materials as photothermal absorbers for sustainable and environmentally friendly energy harvesting

The development of cost-effective and environmentally friendly solar thermal technologies that deliver high performance poses several challenges, where the collector and absorber components play a pivotal role. This research addresses these issues by investigating enhanced temperature generation using a 30 cm × 30 cm Fresnel lens collector under solar illumination from a xenon lamp. Natural stone materials (andesite, coal, and pumice), characterized by granular structures with an average diameter of 1.68-2.00 mm, were selected because of their abundance and eco-friendliness. This research is focused on evaluating the effect of Fresnel lens on temperature generation performance. Two types of temperature generation tests were carried out: wet tests (where the natural stone materials were immersed in distilled water) and dry tests (where the natural stone materials were used in dry conditions). The morphologies of the natural stone materials were examined using an optical microscope and scanning electron microscope. Furthermore, the optical properties of the natural stone materials were analyzed using an ultraviolet-visible (UV-VIS) spectrophotometer. The findings revealed that there were significant improvements in the photothermal absorber performance with the use of a Fresnel lens in dry tests, where the highest temperature was achieved for coal (103.25 °C), followed by andesite (89.00 °C) and pumice (73.00 °C). The impurities varied between the materials, where the impurities were most dominant for pumice while coal was more uniform. Further examination using scanning electron microscope showed that all materials had light-trapping structures in the form of rough surfaces, pores, and crack gaps. Andesite was dominated by rough surfaces, while coal and pumice were dominated by crack gaps and pores, respectively. However, based on the UV-VIS spectrophotometric results, there were no correlations between the optical properties (absorbance, reflectance, and transmittance) and temperature achieved by the photothermal absorber materials. This research demonstrates the potential of using natural stone materials as photothermal absorbers in combination with a Fresnel lens collector for low-to-medium temperature solar thermal applications.