Search results for "doping"
showing 10 items of 801 documents
Excitonic luminescence in ZnO nanopowders and ceramics
2009
Abstract Fast photoluminescence spectra in the spectral region of 3.1–3.45 eV in ZnO and ZnO:Al ceramics were studied at 14 and 300 K. Ceramics with grains smaller than 100 nm were sintered from nanopowders by high pressure (8 GPa) and low temperature (350 °C). Ceramics with grain sizes 1–5 μm were sintered at 1400 °C. It is shown that excitonic luminescence spectra depend on the ceramics grain size, post preparing annealing and doping. The excitonic luminescence decay time was faster than 2 ns and the afterglow at 30 ns was ∼0.05%.
Enhanced optical properties of Cd–Mg-co-doped ZnO nanoparticles induced by low crystal structure distortion
2020
Abstract The growth of CdxMg0.125-xZn0.875O nanoparticles with yellow-orange luminescence is achieved up to 2.5 at. % Cd via a modified sol–gel process. X-ray diffraction analysis confirmed that all the nanoparticles have the hexagonal wurtzite structure. It is found that Cd doping has a considerable effect on the crystal size, microstrain, band gap, and photoluminescence of the Mg0·125Zn0·875O structure, originating from a preferred crystallographic orientation along the (101) plane of the wurtzite structure. The shift and broadening of the E2(high) mode observed in the Raman spectra due to growth-induced strain corroborates the small distortion observed in the X-ray diffraction data. The …
Luminescence properties of Eu, RE3+ (RE = Dy, Sm, Tb) co-doped oxyfluoride glasses and glass–ceramics
2017
Abstract Eu, RE3+ (RE = Dy, Sm, Tb) co-doped SiO2–CaF2–Al2O3–CaO oxyfluoride glasses have been prepared by the melt quenching method. By heating the precursor glasses at 670 °C for 1 h, glass–ceramics containing CaF2 nanocrystallites were obtained. DTA and XRD measurements were performed. Excitation spectra of the prepared samples as well as photoluminescence spectra at the excitation of 355 nm and 450 nm were measured, CIE colour coordinates and colour rendering indexes were found. In the glass–ceramics the presence of Eu2+ ions was observed by a broad emission band in the 400–500 nm spectral range. The most promising doping combinations for white light luminophores within our research are…
Fermi energy dependence of the optical emission in core/shell InAs nanowire homostructures.
2017
InAs nanowires grown by vapor–liquid–solid (VLS) method are investigated by photoluminescence. We observe that the Fermi energy of all samples is reduced by ~20 meV when the size of the Au nanoparticle used for catalysis is increased from 5 to 20 nm. Additional capping with a thin InP shell enhances the optical emission and does not affect the Fermi energy. The unexpected behavior of the Fermi energy is attributed to the differences in the residual donor (likely carbon) incorporation in the axial (low) and lateral (high incorporation) growth in the VLS and vapor–solid (VS) methods, respectively. The different impurity incorporation rate in these two regions leads to a core/shell InAs homost…
Defect formation in photochromic Ca2SnO4: Al3+
2021
Abstract Photoluminescence, photochromism and defect formation were analysed in Ca2SnO4 doped with 0–20% Al3+. Bright cyan luminescence attributed to Sn2+ was detected in all samples. Introduction of Al3+ in Ca2SnO4 led to an enhancement of Sn2+ emission by up to 70% in comparison with an undoped sample. After exposure to UV irradiation, two absorbance bands centered at 520 nm and 710 nm and three paramagnetic defects were observed in Al3+-doped Ca2SnO4 samples. The paramagnetic centers were identified as a hole type and two different Sn3+ centers. Electron paramagnetic resonance (EPR) data suggested that one of the Sn3+ centers is located in a close proximity of Al3+. Analysis of the stabi…
Excitation and photoluminescence spectra of single- and non-single-phased phosphors based on LaInO3 doped with Dy3+, Ho3+ activators and Sb3+ probabl…
2017
Abstract Single-phased La 0.95 Ln 0.05 InO 3 ( Ln – Dy, Ho), La 0.90 Dy 0.05 Ho 0.05 InO 3 , LaInO 3 ceramic samples as well as the La 0.95 Ln 0.05 In 0.98 Sb 0.02 O 3 ( Ln – Dy, Ho), La 0.90 Dy 0.05 Ho 0.05 In 0.98 Sb 0.02 O 3 , LaIn 0.98 Sb 0.02 O 3 samples with additional impurity LaSbO 3 phase were prepared by solid-state reactions method. Their excitation and photoluminescence (PL) spectra were measured at room temperature. It was established that PL bands intensity of spectra obtained for samples of nominal composition La 0.95 Dy 0.05 In 0.98 Sb 0.02 O 3 , La 0.95 Ho 0.05 In 0.98 Sb 0.02 O 3 , La 0.90 Dy 0.05 Ho 0.05 In 0.98 Sb 0.02 O 3 is much higher than that of single-phase La 0.95…
Deep-blue thermally activated delayed fluorescence (TADF) emitters for light-emitting electrochemical cells (LEECs)
2017
The authors acknowledge the University of St Andrews for financial support. The authors also acknowledge financial support from the European Union H2020 project INFORM (grant 675867), the Spanish Ministry of Economy and Competitiveness (MINECO) via the Unidad de Excelencia María de Maeztu MDM-2015-0538, MAT2014-55200 and the Generalitat Valenciana (Prometeo/2016/135). MLP acknowledges support from a Grisolia grant (GRISOLIA/2015/A/146). Two deep blue thermally activated delayed fluorescence (TADF) emitters ( imCzDPS and imDPADPS ) that contain charged imidazolium groups tethered to the central luminophore were designed and synthesized as small molecule organic emitters for light-emitting e…
Engineering Sr-doping for enabling long-term stable FAPb1xSrxI3 quantum dots with 100% photoluminescence quantum yield
2021
The Pb substitution in quantum dots (PQDs) with lesser toxic metals has been widely searched to be environmentally friendly, and be of comparable or improved performance compared to the lead-perovskite. However, the chemical nature of the lead substitute influences the incorporation mechanism into PQDs, which has not been explored in depth. In this work, we analyzed Sr-doping-induced changes in FAPbI3 perovskites by studying the optical, structural properties and chemical environment of FAPb1−xSrxI3 PQDs. The substitution of Pb by 7 at% Sr allows us to achieve FAPb1−xSrxI3 PQDs with 100% PLQY, high stability for 8 months under a relative humidity of 40–50%, and T80 = 6.5 m…
Sub-band-gap-excited luminescence of localized states in SiO2–Si and SiO2–Al glasses
2010
Abstract Silica glass samples doped with extra silicon (SiO 2 –Si: artificial oxygen deficiency) and with aluminum (SiO 2 –Al: Al-doped without accompanying alkali ions) were studied. The luminescence properties of these two samples are compared in the range of temperature 15–290 K under excitation of ArF excimer laser (193 nm). In both samples the luminescence of oxygen deficient centers (ODCs) is detected, i.e., emission bands in the blue at 440 nm and the UV at 280 nm. Cooling of the both samples led to strong increases of luminescence intensity down to 80 K with much smaller increases for still lower temperatures. At 290 K in SiO 2 –Si a luminescence similar to that of twofold-coordinat…
Luminescence in SrTiO3and LiNbO3Crystals Under High Density Pulsed Electron Excitation
2004
The time-resolved luminescence as well as stationary excited luminescence in SrTiO3 (undoped, Nb and Pb doped) and LiNbO3 (congruent and stoichiometric) single crystals was studied. The charge-transfer vibronic exciton in the regular oxy-anion site is suggested to be responsible for luminescence bands at 2.8 eV and 2.75 eV for SrTiO3 and LiNbO3 crystals respectively. It is suggested that luminescence band observed in SrTiO3 at ∼2.2-2.3 eV above 80 K possibly is due to some defect common for all SrTiO3 crystals studied.