Search results for "Semiconductor"
showing 10 items of 974 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.
Effect of reactive ion beam etching on the photoluminescence of CdTe epitaxial layers
2008
http://link.aip.org/link/?JAPIAU/103/056108/1
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…
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 …
Structural and luminescence properties of GaN nanowires grown using cobalt phthalocyanine as catalyst
2015
Catalyst free methods have usually been employed to avoid any catalyst induced contamination for the synthesis of GaN nanowires with better transport and optical properties. Here, we have used a catalytic route to grow GaN nanowires, which show good optical quality. Structural and luminescence properties of GaN nanowires grown by vapor-liquid-solid technique using cobalt phthalocyanine as catalyst are systematically investigated as a function of various growth parameters such as the growth temperature and III/V ratio. The study reveals that most of the nanowires, which are several tens of microns long, grow along [101¯0] direction. Interestingly, the average wire diameter has been found to …
Growth, structural and optical properties of GaN/AlN and GaN/GaInN nanowire heterostructures
2012
Abstract After discussing the GaN NW nucleation issue, we will present the structural properties of axial and radial (i.e. core/shell) GaN/AlN NW heterostructures and adress the issue of critical thickness during the growth of such heterostructures. Next, we will present the growth of InGaN NWs on a GaN NW base. It will be shown that the morphology and structural properties of the InGaN NW sections depend on the In content: for high In content a flat top is observed and plastic relaxation is occuring, with mismatch dislocations formed at the InGaN/GaN interface. By contrast, for In content below 25% InGaN NWs exhibit a pencil-like shape assigned to a purely elastic strain relaxation process…
Characterization of the ESR response of alanine dosimeters to low-energy Cu-target X-tube photons
2017
Abstract This article describes Electron Spin Resonance (ESR) response measurements of Kodak BioMax alanine films exposed to low-energy X-rays from a Cu-target tube operating at 20 kV. Commercial alanine detectors were used to ensure maximum reproducibility of the results, while the choice of a film was due the low penetration of the soft X-rays. X-ray energy spectra and fluences were determined with an innovative digital semiconductor detector system. These data were used to quantify the irradiation of the alanine films in terms of absorbed dose to water. The alanine films were found to present a stable response, highly linear with dose. To our knowledge, these data have not been previousl…
Transient photoresponse and incident power dependence of high-efficiency germanium quantum dot photodetectors
2012
We report a systematic study of time-resolved and power-dependent photoresponse in high-efficiency germanium quantum dot photodetectors (Ge-QD PDs), with internal quantum efficiencies greater than 100 over a broad wavelength, reverse bias, and incident power range. Turn-on and turn-off response times (τ on and τ off) are shown to depend on series resistance, bias, optical power, and thickness (W QD) of the Ge-QD layer, with measured τ off values down to ∼40 ns. Two different photoconduction regimes are observed at low and high reverse bias, with a transition around -3 V. A transient current overshoot phenomenon is also observed, which depends on bias and illumination power. © 2012 American …
Limits on the release of Rb isotopes from a zeolite based 83mKr calibration source for the XENON project
2011
The isomer 83mKr with its half-life of 1.83 h is an ideal calibration source for a liquid noble gas dark matter experiment like the XENON project. However, the risk of contamination of the detector with traces of the much longer lived mother isotop 83Rb (86.2 d half-life) has to be ruled out. In this work the release of 83Rb atoms from a 1.8 MBq 83Rb source embedded in zeolite beads has been investigated. To do so, a cryogenic trap has been connected to the source for about 10 days, after which it was removed and probed for the strongest 83Rb gamma-rays with an ultra-sensitive Germanium detector. No signal has been found. The corresponding upper limit on the released 83Rb activity means tha…
Temperature-dependent magnetic anisotropy in the layered magnetic semiconductors CrI3 and CrBr3
2018
Chromium trihalides are layered and exfoliable semiconductors and exhibit unusual magnetic properties with a surprising temperature dependence of the magnetization. By analyzing the evolution of the magnetocrystalline anisotropy with temperature in chromium iodide $\mathrm{Cr}{\mathrm{I}}_{3}$, we find it strongly changes from ${K}_{u}=300\ifmmode\pm\else\textpm\fi{}50\phantom{\rule{4pt}{0ex}}\mathrm{kJ}/{\mathrm{m}}^{3}$ at $5\phantom{\rule{4pt}{0ex}}\mathrm{K}$ to ${K}_{u}=43\ifmmode\pm\else\textpm\fi{}7\phantom{\rule{4pt}{0ex}}\mathrm{kJ}/{\mathrm{m}}^{3}$ at $60\phantom{\rule{4pt}{0ex}}\mathrm{K}$, close to the Curie temperature. We draw a direct comparison to $\mathrm{CrB}{\mathrm{r}}_…