Search results for "doping"
showing 10 items of 801 documents
Impact of fluorine admixture, hydrogen loading, and exposure to ArF excimer laser on photoluminescence of bismuth defects in amorphous silica
2013
Abstract Photoluminescence (PL) excited by ArF (193 nm), KrF (248 nm) and N 2 (337 nm) pulsed lasers is studied in bismuth doped unfused silicon dioxide synthesized on silica substrates by surface-plasma chemical vapor deposition (SPCVD). Additive free and fluorinated (F content ~ 0.4 wt.%) amorphous silica are examined as host materials for bismuth. Three typical PL bands peaking at wavelengths of 650 nm (orange), 800 nm and 1400 nm (near infrared, NIR) were observed. It is found that fluorine additive weakly affects PL detail of as deposited samples. However, hydrogen loading completely deactivates NIR PL in the case of fluorine free sample, but only slightly suppresses the NIR band in fl…
Optical characterization of Mg-doped GaN films grown by metalorganic chemical vapor phase deposition
2000
Scanning electron microscopy, micro-Raman, and photoluminescence (PL) measurements are reported for Mg-doped GaN films grown on (0001) sapphire substrates by low-pressure metalorganic chemical vapor phase deposition. The surface morphology, structural, and optical properties of GaN samples with Mg concentrations ranging from 1019 to 1021 cm−3 have been studied. In the scanning micrographs large triangular pyramids are observed, probably due to stacking fault formation and three-dimensional growth. The density and size of these structures increase with the amount of magnesium incorporated in the samples. In the photoluminescence spectra, intense lines were found at 3.36 and 3.31 eV on the tr…
Growth and optical characterization of indirect-gap AlxGa1−xAs alloys
1999
Nonintentionally doped AlxGa1−xAs layers with 0.38 x 0.84 were grown on (100) GaAs substrates by liquid phase epitaxy (LPE) under near-equilibrium conditions. The crystalline quality of the samples was studied by photoluminescence at 2 K and room temperature Raman spectroscopy. The peculiar behavior in the photoluminescence intensities of the indirect bound exciton line and the donor–acceptor pair transition is explained from the evolution of the silicon donor binding energy according to the aluminum composition. It was also possible to observe the excitonic transition corresponding to the AlxGa1−xAs/GaAs interface, despite the disorder and other factors which are normally involved when gro…
Effect of Ga content on luminescence and defects formation processes in Gd3(Ga,Al)5O12:Ce single crystals
2018
The work was supported by the Institutional Research Funding IUT02-26 of the Estonian Ministry of Education and Research and the project 16-15569S of the Czech Science Foundation.
On low-temperature luminescence quenching in Gd3(Ga,Al)5O12:Ce crystals
2019
The work was supported by the ERDF funding in Estonia granted to the Center of Excellence TK141 “Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelec-tronics“ (project No. 2014-2020.4.01.15-0011). Partial support of the projects from the Ministry of Education, Youth and Sports of the Czech Republic no. LO1409, LM2015088 and CZ.02.1.01/0.0/0.0/16 013/ 0001406 is also gratefully acknowledged.
Influence of fluorine on the fiber resistance studied through the nonbridging oxygen hole center related luminescence
2013
The distribution of Non-Bridging Oxygen Hole Centers (NBOHCs) in fluorine doped optical fibers was investigated by confocal microluminescence spectroscopy, monitoring their characteristic 1.9 eV luminescence band. The results show that these defects are generated by the fiber drawing and their concentration further increases after c irradiation. The NBOHC concentration profile along the fiber provides evidence for an exponential decay with the fluorine content. This finding agrees with the role of fluorine in the fiber resistance and is discussed, from the microscopic point of view, by looking at the conversion mechanisms from strained bonds acting as precursors.
The time-resolved luminescence characteristics of Ce and Ce/Pr doped YAG ceramics obtained by high pressure technique
2012
Abstract Transparent Ce and Ce/Pr doped YAG ceramics were prepared under high pressures (up to 8 GPa) and relative low temperature (450 °C). Grain size of the ceramics is less than 50 nm. However unknown defects or disorders strains on grain boundaries caused the additional absorption in these ceramics. The luminescence intensity, spectra and the decay time dependence on pressure applied during ceramic preparation were studied. Concentration of some intrinsic point defect was reduced under the high pressure applied for sintering process. It is shown that formation time of the excited state of Ce luminescence depends on the pressure applied during ceramic sintering.
Self-absorption in a light-emitting electrochemical cell based on an ionic transition metal complex
2015
We report on the quantitative and qualitative effects of self-absorption in light-emitting electrochemical cells (LECs) based on ionic transition metal complexes (iTMCs), as measured in-situ during electric driving. A yellow-emitting iTMC-LEC comprising an active material thickness of 95 nm suffers a 4% loss of the emission intensity to self-absorption, whereas the same type of device but with a larger active-material thickness of 1 mu m will lose a significant 40% of the light intensity. We also find that the LEC-specific effect of doping-induced self-absorption can result in a drift of the emission spectrum with time for iTMC-LECs, but note that the overall magnitude of doping-induced sel…
Potential and limitations of CsBi3I10 as a photovoltaic material
2020
Herein we demonstrate the dry synthesis of CsBi3I10 both as a free-standing material and in the form of homogeneous thin films, deposited by thermal vacuum deposition. Chemical and optical characterization shows high thermal stability, phase purity, and photoluminescence centered at 700 nm, corresponding to a bandgap of 1.77 eV. These characteristics make CsBi3I10 a promising low-toxicity material for wide bandgap photovoltaics. Nevertheless, the performance of this material as a semiconductor in solar cells remains rather limited, which can be at least partially ascribed to a low charge carrier mobility, as determined from pulsed-radiolysis time-resolved microwave conductivity. Further dev…
Optical and structural properties of Al 2 O 3 doped ZnO nanotubes prepared by ALD and their photocatalytic application
2018
Abstract Al2O3 doped ZnO nanotubes with controlled ratio of Al2O3 were successfully designed by combining the two techniques of atomic layer deposition (ALD) and electrospinnig. In order to study the effect of Al2O3 doping on optical and structural properties of Al2O3 doped ZnO nanotubes, the prepared samples were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FTIR), reflectance emission and room temperature photoluminescence (PL). The photocatalytic activity and stability of these materials under UV light was studied by the photodegradation of methyl orange (MO). The results indicate that Al2O…