An experimental investigation was conducted to explore spectroscopic and structural characterization of semiconducting yttrium oxide thin film deposited at 623 K (±5K) utilizing reactive pulsed ...direct current magnetron sputtering. Based on the results obtained from both x-ray diffraction and transmission electron microscope measurements, yttrium monoxide is very likely formed in the transition region between β-Y2O3 and α-Y2O3, and accompanied by the crystalline Y2O3. Resulting from either the low energy separation between 4d and 5s orbitals and/or different spin states of the corresponding orbitals’ sublevels, the stability of monoxide is most presumably self-limited by the size of the crystal in thermodynamic terms. This behavior develops a distortion in the structure of the crystal compared to the metal oxide cubic structure and it also effectuates the arrangement in nanocrystalline/amorphous phase. In addition to this, spectroscopic ellipsometry denotes that the semiconducting yttrium oxide has the dominant, mostly amorphous, formation character over crystalline Y2O3. Our purpose, by means of the current findings, is to advance the understanding of formation kinetics/conditions of yttrium with an unusual valency (2+).
•Yttrium oxidizes in the presence of low partial oxygen pressure (∼10−7 Pa).•β-Y2O3 forms simultaneously with metallic Y crystal.•Divalent yttrium forms along with trivalent yttrium.•The formation of YO shows amorphous character mostly.
Metal nanoparticle formation using laser ablation of targets in water by picosecond pulses is a well-developed process. Here we demonstrate how the salt and sugar being dissolved in water differently ...affect the spectral characteristics of the absorbance of the suspensions produced during ablation of silver and gold targets. We demonstrate the disappearance of the surface plasmon resonances of Ag and Au nanoparticles in the salt-containing solutions. The presence of salt does not allow for maintaining the synthesis of nanoparticles during ablation of metals contrary to the sugar-containing solution. Our nonlinear optical studies show that the saturable absorption observed in the nanoparticles-containing suspensions produced during laser ablation of silver and gold in distilled water and sugar-containing water entirely disappears in the case of the suspension produced during the ablation of these metals in salt-containing solution.
We demonstrate high conversion efficiency towards the third harmonic (TH) of the 900–1700 nm, 150 fs laser in the thin (40–120 nm) films containing quantum dots (HgTe, HgSe, and PbS) and exfoliated ...nanoparticles (Bi
2
Te
3
) deposited on the glass substrates. The ratio of TH conversion efficiencies in the films and glasses of the same thickness was estimated to be > 10
4
. The intensity, polarization, and spectral dependencies of this process in thin films are reported. We discuss the relation between the TH process and the low-order nonlinear optical properties of these quantum dots and nanoparticles.
Native defect-induced photoluminescence around 400nm (blue luminescence - BL) was studied in hBN materials with different size and various origins. The following spectral characterizations were used: ...spectra of luminescence and its excitation, luminescence dependence on temperature, luminescence kinetics, optically stimulated luminescence and infrared absorption. It was found, that the BL is characteristic for all these materials, which were studied. The BL forms a wide, asymmetric and phonon-assisted emission band at 380nm. This luminescence can be excited either through the exciton processes, or with light from two defect-induced excitation bands at 340nm and 265nm. It was found that the BL is caused by two luminescence mechanisms. One of them is intra-center luminescence mechanism (340nm excitation), but the other one is recombination mechanism (265nm excitation). It was considered that the most probable candidates for the defects, which cause the BL in hBN can be related to the nitrogen vacancy type-centers. It was certainly confirmed, that presence of oxygen gas is partly quenching the BL intensity, thus ranking the hBN material among the materials prospective for development of oxygen gas optical sensors.
•Defect-induced luminescence at 380nm is observed for hBN powders.•A phonon-assisted structure is characteristic for 380nm luminescence.•The defect-related excitation of 380nm luminescence is at 340nm and 265nm.•The 380nm luminescence is caused by a recombination or an intra-center mechanism.•The 380nm luminescence is sensitive to oxygen gas environment.
Laser-induced breakdown spectroscopy (LIBS) provides a rapid, cost-effective, and extra-sensitive analysis of geological samples to make preliminary conclusions about the presence of valuable ...elements up to the trace levels in the ore. We present the first results of a highly sensitive qualitative analysis of the core samples of geological ore from two boreholes in Latvia (Staicele 1, from a depth range of 794–802 m, and Garsene (Subate) 2A, from a depth range of 1102–1103 m) using LIBS. Our measurements using this technique confirmed the high iron content and indicated traces of rare and high in-demand metals (such as Ti, V, Co, Sm, etc.) in the sample from Staicele, renewing interest in studying boreholes across Latvia. The presented pilot studies demonstrated effectiveness and unique possibility in performing a very sensitive and time-saving qualitative analysis of the composition of samples of ores from the old but still valuable borehole cores by using the LIBS method. We compare these measurements with other methods of sample analysis.
•A fast and long-lasting recombination luminescence processes in AlN:Mn2+ are observed.•Complex decay processes for 600 nm PersL in AlN:Mn2+ are observed.•The mechanisms of 600 nm recombination ...luminescence in AlN:Mn2+ are proposed.
Luminescence processes resulting in 600 nm emission of Mn2+ ions in AlN:Mn ceramics were studied based on investigations of photoluminescence and its excitation spectra, luminescence kinetics and long-lasting luminescence (PersL) properties. For AlN:Mn2+ nanopowders, the photoluminescence spectra and PersL were studied. Luminescence properties were examined and compared after the samples were irradiated with 520 nm light, resulting in direct excitation of Mn2+ ions, thus causing the intra-center luminescence, or with 263 nm light. As known, in the last case, the oxygen-related defects are primarily excited with the following energy transfer to Mn2+ ions and 600 nm emission, thus forming the recombination luminescence (RecL). Two types of excitations of the 600 nm RecL were used. In the first case, the luminescence response was detected during the sample irradiation with 263 nm light. It was found that at RT, the decay of the RecL is fast and its decay constant τ = 1.2 ms coincides with the value obtained for the intra-center luminescence. A time-dependent rise of the 600 nm luminescence intensity under 263 nm excitation was observed. In the other case, the 600 nm RecL was detected when irradiation of the sample with 263 nm light was ceased, and spectra and decay of PersL were studied. It was found that the decay of 600 nm PersL spectra could be described using three exponential functions, thus manifesting a variety of luminescence processes. The results allow tracing of the luminescence processes and proposal of the mechanisms resulting in the 600 nm light emission of Mn2+ ions. An energy level scheme of AlN:Mn2+ was constructed to elucidate of the luminescence processes and mechanisms.
Optical thermometers are advantageous for temperature measurement in electromagnetic fields and aggressive environments; however, their composition mostly relies on materials doped with expensive and ...resource-limited rare earth ions.
In this article, we describe the application of calcium aluminate doped with transition metal ions (Mn
and Cr3+) in optical thermometry, employing optical fibres for signal transmission. Upon excitation with 450 nm laser diode radiation, changes in the luminescence of Mn
ions in the 500–550 nm band are followed along with changes in the Cr
band at 750–800 nm.
The application has been tested in the temperature range from 20 °C to 800 °C. The temperature dependence of Cr
luminescence encompasses the high-temperature range, whereas the luminescence band of Mn
ions gives an increase in the total intensity and provides a more consistent change in the range from 400 °C to 550 °C.
PDF
