Optical Materials: X最新文献

Tin dioxide (SnO₂) is an oxide semiconductor with n-type characteristics, with high transparency in the UV–Vis, where the donors are usually associated with oxygen vacancies and interstitial tin ions. Quinoline derivatives (QD) are usually p-type semiconductors with emission in the blue range. We report photo-induced properties of the QD 4-(6-(diethylamino)-4-phenylquinolin-2-yl)benzoic acid and the combination with the inorganic semiconductor oxide SnO₂, both layers in the form of thin film, which forms a heterostructure. Thin film is a very convenient format for integration in optoelectronics. Emission of the QD takes place in blue range (470–485 nm) and depends on the solvent when in solution, being used acetone and tetrahydrofuran (THF). However, when in the form of thin film, it does not depend on the solvent. Concerning the heterostructure, it is explored under distinct device architecture: 1) combination in a transport profile perpendicular to the films (transverse contacts) leading to a rectifying behavior similar to a p-n junction, which is evidence of the p-type-like electrical behavior of the QD; 2) in parallel conduction profile, where there seems to exist some sort of interfacial phenomenon similar to a two-dimensional electron gas (2-DEG), a property that can be explored in transparent high-mobility transistors.

Due to growing concerns considering environmental pollution, interest in bioplastics is rising. For technical applications, the respective materials have to meet high requirements. In optical applications these include transmittance, refractive index and dispersion but also dimensional stability, resistance against thermal influences and radiation induced degradation. Polylactide (PLA), a bio-based and biodegradable polymer, is already applied in high tech applications such as bioresorbable implants. The material shows favorable optical properties in its glassy state and excellent resistance against photodegradation. However, the application of PLA is hindered by its crystallization behavior. When exposed to temperatures above 55–60 °C it turns hazy. This might be avoided by hindering crystallization or tailoring crystal morphology. In this critical review, current applications of PLA are discussed and its broad use is shown. A literature search is carried out considering fully bio-based and biodegradable plastics for optical applications. The results show that currently no material is commercially available that meets all requirements set. Finally, an overview of the current state in research is provided, considering PLA-based materials with adapted crystallization behavior under the aspect of transparency. This includes use of additives, formulation of blends and material treatments. Finally, recommendations for the goal of achieving highly sustainable PLA-based optical components are given.

Optical functional materials such as nanostructured silicates have been studied for photonics applications involving energy conversion. In this scenario, we studied Zn₂SiO₄:Mn²⁺ nanostructured powders prepared by combustion synthesis for optical thermometry based on photon downshifting. The structural analysis showed that Zn₂SiO₄ particles were found embedded in clustered silica nanoparticles. The photoluminescence analysis showed that the samples exhibit intense green emission (centered around 525 nm), corresponding to the electronic transition ⁴T₁ → ⁶A₁ of Mn²⁺, when exposed to a low power ultraviolet lamp (centered around 255 nm). The temperature sensing performance of this material was evaluated using three different methodologies, i.e. the luminescence decay time constant, the spectral full width at half maximum, and the luminescence peak intensity from the ⁴T₁ → ⁶A₁ radiative transition. The thermometric analysis based on luminescence peak intensity provided a maximum relative sensitivity of ∼4.9x10⁻³ K⁻¹ at 498 K, while the decay lifetime and the spectral width at half maximum provided maximum relative temperature sensitivities of ∼2.9x10⁻³ K⁻¹ at 523 K and ∼1.7x10⁻³ K⁻¹ at 298 K, respectively.

The pyrochlore-structured (A₂B₂O₇) compounds have emerged as a focal point in contemporary research and materials science, captivating attention for their intriguing properties such as photoluminescence, superconductivity, ionic mobility, and potential applications in high-temperature barrier coatings. Their potential application in up- or down-conversion photoluminescence further positions them for integration into a myriad of optoelectronic and sensing devices. Building on extensive prior research, this review delves into the upconversion (UC) luminescence properties of numerous pyrochlore-structured host materials (titanates, zirconates, hafnates, and ytterbium pyrochlores), specifically those doped with rare earth ions. While these materials may share similar chemical and structural characteristics, their luminescent capabilities exhibit significant variation upon rare earth ion doping. The phase transitions of various pyrochlore-structured compounds with respect to cation ratio, the relationship between crystal structure, doping concentrations, and UC luminescent properties in pyrochlore-structured compounds are summarized in detail. Through controlled doping strategies and structural adjustments, researchers have been able to tailor the luminescence properties of pyrochlore structured compounds to meet specific application requirements. The intricate exploration of the UC luminescence properties of pyrochlore-structured compounds, especially when doped with rare earth ions, showcases the rich potential for these materials in a wide array of applications across various fields, from advanced sensing technologies to innovative optoelectronic devices, paving the way for exciting advancements in materials science and beyond.

In order to demonstrate the application of terahertz time-domain ellipsometry (THz-TDE) in the characterization of wide-bandgap semiconductors, we studied two zinc oxide (ZnO) single crystals with different conductivities. The optical properties of ZnO samples with low conductivity and high conductivity are both obtained by ellipsometric parameters, while the electrical properties of ZnO sample with high conductivity are well deduced and fitted using the Drude model. These results suggest that THz-TDE can effectively obtain the optical and electrical properties of wide-gap semiconductors and can be used to characterize semiconductors with carrier densities higher than 10¹⁶ cm⁻³.

This paper reviews the main literature describing models for thermoluminescence (TL), optically stimulated luminescence (OSL) and radiophotoluminescence (RPL) in aluminosilicate materials, namely natural feldspar minerals and synthetic glasses. The work examines the different models proposed to explain the various luminescence phenomena and compares them with each other. The models include thermally and optically stimulated excited-state tunneling, band-tail state hopping, and ionization and transportation through the band-tail states and/or the conduction band. Temperature and stimulation wavelength are critical parameters, with one model or another dominating over different temperature and/or wavelength ranges. Some recommendations for future research are noted.

The necessary information on the formation of high manganese silicide (Mn₄Si₇) coating by magnetron sputtering method is presented in this work. The technology and basic modes of creating the necessary targets for a magnetron sputtering device are presented. Targets were created by adding silicon and manganese powders in the required amount and heating them under vacuum conditions at high temperature and pressure. Thin silicide films (thin coatings) of different thicknesses were formed on the surface of silicon dioxide from the produced targets using the method of magnetron sputtering. The electrophysical and thermoelectric properties of the produced films were studied using physical and optical methods.Due to the change in the structure of the coatings during subsequent heat treatment, the Seebeck coefficient noticeably increases.

This work is devoted to examining the influence of energy transfer processes between Ce³⁺ and Pr³⁺ ions on the luminescent and scintillation properties of LuAG:Ce and LuAG:Ce,Pr scintillators, grown by liquid phase epitaxy onto undoped LuAG substrates with a PbO–B₂O₃-based flux. To characterize them, measurements of the absorption, cathodoluminescence, photoluminescence emission and excitation spectra as well as the photoluminescence decay kinetics of the SCFs under study were performed. The investigation confirmed simultaneous energy transfer processes between d-f and f-f states of Pr³⁺ ions and between Pr³⁺ (d-f) and Ce³⁺ (d-f) ions, as well as from Ce³⁺ (d-f) to Pr³⁺ (f-f) ions in LuAG host. Furthermore, the energy transfer from Pb²⁺ flux-related impurity to Ce³⁺ (d-f) and Pr³⁺ (f-f) ions also were found in the LuAG:Ce and LuAG:Ce,Pr SCFs. An energy diagram of the Pb²⁺, Pr³⁺ and Ce³⁺ ion levels was constructed, which provides a deeper overview of the mentioned energy transfer processes.

Plasma fluctuation dispersion has been theoretically and experimentally studied in monocrystal samples of Si (111) and Ge (111). It has been shown that the dispersion depends on crystallographic orientations of materials under study. In this work, the dispersion effects in the CLEE spectra, which manifest themselves in bulk samples of Si and Ge, have been studied. The loss energy electron was studied by the CLEE method upon their reflection from Si(111) and Ge(111) at different angles of incidence of the electron beam on the surface. Calculation of the total electron energy loss with formula (5) shows that the form of the CLEE spectrum of primary electrons depends on the nature and magnitude of the electron density in a given direction and is in satisfactory agreement with the experimental data. Thus, the theoretical and experimental results show that in the case of single-crystalline Si and Ge, with increasing k, the values of the bulk plasma oscillation increase by 2–3 eV.

The optical spectroscopy and the decay kinetics of samples with composition Sr₃Yb(PO₄)₃, Sr₃Y_0.98Yb_0.02(PO₄)₃, Sr₃Y_0.98Er_0.02(PO₄)₃ and Sr₃Yb_0.98Er_0.02(PO₄)₃ have been studied at room temperature. The presence of efficient energy transfer and migration processes has been clearly evidenced in the Sr₃Yb(PO₄)₃ and Sr₃Yb_0.98Er_0.02(PO₄)₃ materials, giving rise to strong visible upconversion upon excitation in the spectral region around 1 μm in the latter material. The strong anti-Stokes emission is connected to fast migration in the ²F_5/2 level of Yb³⁺, due to the inefficient concentration quenching for this ion. In this class of materials, the upconversion processes could be optimized even in the presence of high concentrations of the Yb³⁺ sensitizer.