Search results for "RADIATION"
showing 10 items of 5298 documents
Frontispiece: A Novel High‐Pressure Tin Oxynitride Sn 2 N 2 O
2020
Chemistry - a European journal 26(10), 2187-2194 (2020). doi:10.1002/chem.202081063
Measurement of drift mobilities in amorphous organic films using the Time of Flight method
2004
We apply the Time of Flight (TOF) technique to study carrier mobility in N, N’-diphenyl-N,N’-bis(3-methylphenyl) -1,1-biphenyl-4,4’-diamine (TPD) and tris(8-hydroxyquinolato) aluminium (Alq 3 ). These materials are two examples of, respectively, hole and electron transporting molecular materials. Measurements are performed in free air or under vacuum varying the experimental parameters such as laser pulse intensity and single shot irradiation. We observe a transition from dispersive to non dispersive transport changing the experimental conditions.
Analysis of self-trapped hole mobility in alkali halides and metal halides
2017
Support from Latvian National Research Program IMIS2 (2014–2017) and LZP Grant No. 237/2012 (2013–2016) is greatly appreciated.
Cathodoluminescence study of undoped GaN films: Experiment and calculation
2009
Abstract In this paper, we report the theoretical and experimental results of cathodoluminescence (CL) from GaN layers grown at 800 °C by metal organic vapor phase epitaxy (MOVPE) on silicon substrate. The CL spectra recorded at room temperature reveal the near band-edge emission at 3.35–3.42 eV and a broad yellow luminescence at 2.2 eV. The CL depth analysis at constant power excitation shows inhomogeneous CL distribution in depth of these emissions as the electron beam increases from 3 to 25 keV. There appears a blue shift of the CL band-edge peaks with increasing sample depth. This behavior is explained by a change of the fundamental band gap due to residual strain and the local temperat…
Temperature Dependent Quantum Efficiencies in Multicrystalline Silicon Solar Cells
2015
Abstract Several field studies comparing modules based on Elkem Solar Silicon ® (ESS ® ) cells with reference modules based on non-compensated virgin polysilicon show that the compensated ESS ® modules outperform the reference modules with comparable installed capacity under certain operating conditions. At high temperatures and high irradiation conditions the modules based on compensated silicon produce more energy than the reference modules. In order to increase the understanding of the observed effect cells are studied at different temperatures by the means of IV-characteristics as well as quantum efficiencies. Quantum efficiency measurements show that the main difference between ESS ® c…
Azatruxene‐Based, Dumbbell‐Shaped, Donor–π‐Bridge–Donor Hole‐Transporting Materials for Perovskite Solar Cells
2020
Three novel donor-π-bridge-donor (D-π-D) hole-transporting materials (HTMs) featuring triazatruxene electron-donating units bridged by different 3,4-ethylenedioxythiophene (EDOT) π-conjugated linkers have been synthesized, characterized, and implemented in mesoporous perovskite solar cells (PSCs). The optoelectronic properties of the new dumbbell-shaped derivatives (DTTXs) are highly influenced by the chemical structure of the EDOT-based linker. Red-shifted absorption and emission and a stronger donor ability were observed in passing from DTTX-1 to DTTX-2 due to the extended π-conjugation. DTTX-3 featured an intramolecular charge transfer between the external triazatruxene units and the azo…
Photosensitivity of SiO2–Al and SiO2–Na glasses under ArF (193 nm) laser
2009
Abstract Photosensitivity of SiO 2 –Al and SiO 2 –Na glass samples was probed by means of the induced optical absorption and luminescence as well as by electron spin-resonance (ESR) after irradiation with excimer-laser photons (ArF, 193 nm). Permanent visible darkening in the case of SiO 2 –Al and transient, life time about one hour, visible darkening in the case of SiO 2 –Na was found under irradiation at 290 K. No darkening was observed at 80 K for either kind of material. This investigation is dedicated to revealing the electronic processes responsible for photosensitivity at 290 and 80 K. The photosensitivity of both materials is related to impurity defects excited directly in the case …
Luminescence and electron transport properties of GaN and AlN layers
2001
Abstract The transport properties of free charge carriers, photo- and cathodo-luminescence (CV) in GaN and AlN films obtained by MOCVD technique on sapphire and Si substrates, are investigated. The concentration of free charge carriers in GaN is of order 10 17 – 10 19 cm −3 whereas AlN thin films are insulating. The Hall mobility of electrons are 80– 140 cm 2 / V s ). In undoped GaN films the spectral composition of CL is close to photoluminescence (PL) when excited in the region of band–band transitions. The decay time constant of the 3.44 eV UV emission attributed to the bound exciton is considerably less than 1 ns , whereas the 3.26 eV violet (VI) band shows a slow hyperbolical decay ove…
EPR on Radiation-Induced Defects in SiO2
2014
Continuous-wave electron paramagnetic resonance (EPR) spectroscopy has been the technique of choice for the studies of radiation-induced defects in silica (SiO2) for 60 years, and has recently been expanded to include more sophisticated techniques such as high-frequency EPR, pulse electron nuclear double resonance (ENDOR), and pulse electron spin echo envelope modulation (ESEEM) spectroscopy. Structural models of radiation-induced defects obtained from single-crystal EPR analyses of crystalline SiO2 (alfa-quartz) are often applicable to their respective analogues in amorphous silica (a-SiO2), although significant differences are common.
Electron paramagnetic resonance investigation on the hyperfine structure of the center in amorphous silicon dioxide
2007
Abstract We report an experimental investigation by electron paramagnetic resonance (EPR) spectroscopy on the hyperfine structure of the E δ ′ center in γ-ray irradiated amorphous silicon dioxide materials. This study has driven us to the determination of the intensity ratio between the hyperfine doublet and the main resonance line of this point defect. This ratio was obtained for a variety of silica samples and compared with the analogous ratio obtained for the E γ ′ defect. The comparison definitively confirms that the electronic wave function involved in the E δ ′ center is actually delocalized over four nearly equivalent Si atoms.