Search results for "Absorption"
showing 10 items of 2701 documents
Luminescence properties of LiGaO2 crystal
2017
The study was supported by the Latvia-Lithuania-Taiwan research project “Nonpolar ZnO thin films: growth-related structural and optical properties” (Latvia: LV-LT-TW/2016/5 , Lithuania: TAP LLT 02/2014 , Taiwan: MOST 103-2923-M-110-001-MY3 ).
Optical properties of thin films of ZnO prepared by pulsed laser deposition
2004
In this paper we report on the structural features and optical properties of wurtzite ZnO films epitaxially grown on sapphire, fluorite and mica substrates by means of pulsed laser deposition (PLD). Post-deposition annealing results in a clear improvement of the film quality, reflected by the small width of the exciton-related lines in both the absorption and the photoluminescence spectra. Photoluminescence spectra revealed a multi-line structure which is identified in term of free excitons and excitons complexes with neutral donors and deep centers. The relative intensity of the PL lines mainly depends on the nature of the substrate used. Concerning optoelectronic applications it is especi…
Current status of AlInN layers lattice-matched to GaN for photonics and electronics
2007
We report on the current properties of Al1-x InxN (x approximate to 0.18) layers lattice- matched ( LM) to GaN and their specific use to realize nearly strain- free structures for photonic and electronic applications. Following a literature survey of the general properties of AlInN layers, structural and optical properties of thin state- of- the- art AlInN layers LM to GaN are described showing that despite improved structural properties these layers are still characterized by a typical background donor concentration of ( 1 - 5) x 10(18) cm(-3) and a large Stokes shift (similar to 800 meV) between luminescence and absorption edge. The use of these AlInN layers LM to GaN is then exemplified …
Photoluminescence in ZnO:Co2+ (0.01%–5%) Nanoparticles, Nanowires, Thin Films, and Single Crystals as a Function of Pressure and Temperature: Explori…
2014
This work investigates the electronic structure and photoluminescence properties of Co2+-doped ZnO and their pressure and temperature dependences through high-resolution absorption and emission spe...
The effect of quantum size confinement on the optical properties of PbSe nanocrystals as a function of temperature and hydrostatic pressure
2013
A study based on photoluminescence and absorption measurements as a function of temperature and pressure for PbSe nanocrystals with sizes in the range 3–13 nm reveals the influence of size quantum confinement on the observed variation. In the case of the temperature variation, the effective bandgap changes from showing a positive rate of change to showing a negative one (for a quantum dot 3 nm in diameter), which can be accounted for by incorporating a linear variation of the carrier effective masses into a simple calculation of the exciton ground state in the quantum dot. In the case of the pressure variation, we observe a clear inverse correlation between the absolute value of the pressur…
The evolution of the fraction of Er ions sensitized by Si nanostructures in silicon-rich silicon oxide thin films
2009
Photoluminescence (PL) and time-resolved PL experiments as a function of the elaboration process are performed on Er-doped silicon-rich silicon oxide (SRO:Er) thin films grown under NH(3) atmosphere. These PL measurements of the Er(3+) emission at 1.54 microm under non-resonant pumping with the Er f-f transitions are obtained for different Er(3+) concentrations, ranging from 0.05 to 1.4 at.%, and various post-growth annealing temperatures of the layers. High resolution transmission electron microscopy (HRTEM) and energy-filtered TEM (EFTEM) analysis show a high density of Si nanostructures composed of amorphous and crystalline nanoclusters varying from 2.7 x 10(18) to 10(18) cm(-3) as a fun…
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…
Defect Luminescence of LiBaF3 Perovskites
2000
Blue and red luminescence of undoped LiBaF3 crystals was studied. A broad, isotropic photoluminescence band centered at 410 nm can be excited by 210 nm — 275 nm light in as grown crystals. After X-irradiation at RT a new narrower, anisotropic luminescence band appears at 425 mn which has an additional excitation band at 290 nm. The X-irradiation also creates the F- type centres and anisotropic centres with an absorption band at 630 nm and a luminescence band at 700 nm. No F- centre luminescence is observed. All the other centres mentioned act as radiative recombination centers as well. It is speculated that the origin of the blue luminescence is due to oxygen defects and that the red lumine…
Oxidation of Zn nanoparticles probed by online optical spectroscopy during nanosecond pulsed laser ablation of a Zn plate in H2O
2015
We report online UV-Visible absorption and photoluminescence measurements carried out during and after pulsed laser ablation of a zinc plate in water, which clarify the events leading to the generation of ZnO nanoparticles. A transient Zn/ZnO core-shell structure is revealed by the coexistence of the resonance absorption peak around 5.0 eV due to Zn surface plasmon resonance and the edge at 3.5 eV of ZnO. The growth kinetics of ZnO, selectively probed by the exciton luminescence at 3.3 eV, begins only after a ∼30 s delay from the onset of laser ablation. We also detect the luminescence at 2.3 eV of ZnO oxygen vacancies, yet rising with an even longer delay (∼100 s). These results show that …
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.