Search results for "Optoelectronics"
showing 10 items of 2306 documents
Luminescence properties of wurtzite AlN nanotips
2006
The optical properties of aluminum nitride nanotips (AlNNTs) synthesized via vapor transport and condensation process have been studied by cathodoluminescence, photoluminescence (PL), thermoluminescence (TL), and UV absorption measurements. Two defect related transitions around 2.1 and 3.4eV and an excitonic feature at 6.2eV were identified. Compared to the AlN macropowders, the AlNNTs showed a blueshift (+0.2eV) of the ∼3.2eV peak. Analysis of both PL and TL excitation measurements indicated the existence of subband gap multiple energy levels in AlNNTs. A significant TL intensity even at 145°C suggests possible ultraviolet detector and dosimetric applications of these AlNNTs.
Temperature Sensor Based on Colloidal Quantum Dots PMMA Nanocomposite Waveguides
2012
In this paper, integrated temperature sensors based on active nanocomposite planar waveguides are presented. The nanocomposites consist of cadmium selenide (CdSe) and cadmium telluride (CdTe) quantum dots (QDs) embedded in a polymethylmethacrylate (PMMA) matrix. When the samples are heated in a temperature range from 25$^{circ}{rm C}$ to 50 $^{circ}{rm C}$, the waveguided photoluminescence of QDs suffers from a strong intensity decrease, which is approximately quadratic dependent on temperature. Moreover, the wavelength peak of the waveguided emission spectrum of CdTe-PMMA shows a blue shift of 0.25 ${rm nm}/^{circ}{rm C}$, whereas it remains constant in the case of CdSe-PMMA. A temperature…
The controlled growth of GaN microrods on Si(111) substrates by MOCVD
2015
Abstract In this paper, a selective area growth (SAG) approach for growing GaN microrods on patterned SiN x /Si(111) substrates by metal-organic chemical vapor deposition (MOCVD) is studied. The surface morphology, optical and structural properties of vertical GaN microrods terminated by pyramidal shaped facets (six { 10 1 ¯ 1 } planes) were characterized using scanning electron microscopy (SEM), room temperature photoluminescence (PL) and Raman spectroscopy, respectively. Measurements revealed high-quality GaN microcolumns grown with silane support. Characterized structures were grown nearly strain-free (central frequency of Raman peak of 567±1 cm −1 ) with crystal quality comparable to bu…
Photoluminescence Imaging and LBIC Characterization of Defects in mc-Si Solar Cells
2018
Today’s photovoltaic market is dominated by multicrystalline silicon (mc-Si) based solar cells with around 70% of worldwide production. In order to improve the quality of the Si material, a proper characterization of the electrical activity in mc-Si solar cells is essential. A full-wafer characterization technique such as photoluminescence imaging (PLi) provides a fast inspection of the wafer defects, though at the expense of the spatial resolution. On the other hand, a study of the defects at a microscopic scale can be achieved through the light-beam induced current technique. The combination of these macroscopic and microscopic resolution techniques allows a detailed study of the electric…
Optical, structural, and morphological characterisation of epitaxial ZnO films grown by pulsed-laser deposition
2013
We report on ZnO epitaxial growth by pulsed-laser deposition (PLD) on different substrates, such as quartz, sapphire, and GaN template. Approximately 1 mu m-thick films were grown under different substrate temperatures and background oxygen conditions. X-ray diffraction analysis indicated preferential growth along the c-axis direction with a full-width at half maximum(FWHM) of the rocking curve as narrow as 230 arcs in the case of the GaN template. Low-temperature photoluminescence showed A-excitonic emission near 3.36 eV and a FWHM of (DXA)-X-0 emission as small as 2.89 meV at 9 K. Atomic force microscope measurements showed that roughness as low as 18 nm could be obtained. These results p…
Polarized recombination of acoustically transported carriers in GaAs nanowires
2012
: The oscillating piezoelectric field of a surface acoustic wave (SAW) is employed to transport photoexcited electrons and holes in GaAs nanowires deposited on a SAW delay line on a LiNbO3 crystal. The carriers generated in the nanowire by a focused light spot are acoustically transferred to a second location where they recombine. We show that the recombination of the transported carriers occurs in a zinc blende section on top of the predominant wurtzite nanowire. This allows contactless control of the linear polarized emission by SAWs which is governed by the crystal structure. Additional polarization-resolved photoluminescence measurements were performed to investigate spin conservation d…
Synthesis of multi-color luminescent ZnO nanoparticles by ultra-short pulsed laser ablation
2020
Abstract Crystalline ZnO nanoparticles (NPs) are synthesized by ultra-short femtosecond (fs) pulsed laser ablation (PLA) of a zinc plate in deionized water, and are investigated by optical absorption and time resolved luminescence spectra in combination with the morphology and structure analysis. The comparison with previous experiments based on short nanosecond (ns) PLA highlights that pulse duration is a crucial parameter to determine the size and the optical properties of ZnO NPs. While short PLA generates NPs with average size S ‾ of ~ 30 nm, ultrashort PLA allows to achieve much smaller NPs, S ‾ ⩽ 10 nm, that evidence weak quantum confinement effects on both the absorption edge and th…
Active Media for Optical Data Processing
2002
Peculiarities of colour centre production and their recombination in photostimulated processes in doped alkali halide systems were examined in connection with their practical use as active photostimulable media in miniaturised optoelectronic and photonic devices. The specific interaction of unrelaxed H-centres and electrons with the dopants in different valence and electronic states open a way for widening the scope of multifunctional (logical and mathematical) optical data processing, including the optical chips.
Detailed photoluminescence study of vapor deposited Bi2S3 films of different surface morphology
2014
authorenWe present a temperature- and intensity-dependent photoluminescence (PL) study of the binary semiconductor on the mm-scale and a laterally resolved PL measurement with a resolution of nm. The films can show a rather rough surface with needles and flakes of with different orientations as well as very flat and smooth surface morphology. Despite a band gap of eV the films show a splitting of quasi-Fermi levels (QFL) of meV at room temperature. By means of temperature-dependent PL we have located several radiative and non-radiative defect states in the band gap. For a better understanding of this thin film semiconductor a full analysis of the laterally resolved PL measurement including …
A Luminescent Thermometer Exhibiting Slow Relaxation of the Magnetization: Toward Self-Monitored Building Blocks for Next-Generation Optomagnetic Dev…
2019
The development and integration of Single-Molecule Magnets (SMMs) into molecular electronic devices continue to be an exciting challenge. In such potential devices, heat generation due to the electric current is a critical issue that has to be considered upon device fabrication. To read out accurately the temperature at the submicrometer spatial range, new multifunctional SMMs need to be developed. Herein, we present the first self-calibrated molecular thermometer with SMM properties, which provides an elegant avenue to address these issues. The employment of 2,2′-bipyrimidine and 1,1,1-trifluoroacetylacetonate ligands results in a dinuclear compound, [Dy2(bpm)(tfaa)6], which exhibits slow …