Search results for "doping"
showing 10 items of 801 documents
Morphological and optical property study of Li doped ZnO produced by microwave-assisted solvothermal synthesis
2021
Abstract ZnO materials have been at the centre of many studies for decades. Doping of ZnO by lithium atoms is a prospective approach for compensation of n-type conductivity in the unintentionally doped ZnO aimed at obtaining p-type semiconductor. In this study, we have synthesized ZnO rod-like powders doped with lithium ions (0–0.65 atom%) by the new microwave-assisted solvothermal method in order to obtain greater photoluminescence intensity of ZnO emissions in the UV region. The obtained powders contain nanoparticles from 20 nm up to 250 nm depending on Li content. X-ray diffractometry and Raman spectroscopy were employed to characterise the structure of ZnO powders, scanning electron mic…
Intra-center and recombination luminescence of bismuth defects in fused and unfused amorphous silica fabricated by SPCVD
2013
Abstract Photoluminescence (PL) of bismuth doped silicon dioxide excited by UV excimer lasers (ArF — 193 nm, KrF — 248 nm) and a green light laser diode (532 nm) is studied in a wide spectral band at temperatures ranging from 12 to 750 K. Two types of samples are investigated: unfused, 100 μm in thickness amorphous layer immediately deposited on the inner surface of silica substrate tube, and the same material after profusion resulted from tube collapsing to a rod by external heating. PL bands centered at 620–650 nm, 820 nm and 1400 nm wavelengths are observed in both fused and unfused samples. Under excitation by the green laser diode decay time constants for 650 nm (orange) and 1400 nm (N…
Dynamic doping and degradation in sandwich-type light-emitting electrochemical cells
2012
Photoluminescence spectroscopy has been performed in situ during device operation and after switch-off on ionic transition metal complex (iTMC)-based sandwich-type light-emitting electrochemical cells (LECs). It is demonstrated that the photoluminescence of the LECs decreases with increasing operating time. For operating times up to three hours the decline in photoluminescence is fully recoverable after switching off the bias. These results imply that doping of the iTMC layer is responsible, not only, for the turn-on of LECs but also for their lifetimes.
Comparison of &#x03B3; and &#x03B2;-ray irradiation effects in sol-gel Ge-doped SiO<inf>2</inf>
2009
We report an experimental study on the comparison between the γ or β ray induced Ge related point defects in Ge doped silica. Silica samples doped with ∼2.2 1017 Ge atoms/cm3 produced with the sol-gel technique have been irradiated. The effects of the irradiation have been investigated by optical absorption, photoluminescence and electron paramagnetic resonance spectroscopy in order to evaluate the generation and the dependence on dose of the Ge(1), E'Ge, Germanium Lone Pair Center (GLPC) and H(II) point defects. No relevant differences between the concentrations of γ or β ray induced Ge(1) and E'Ge point defects have been observed. In addition, it is found that both irradiations are able t…
Study of the germanium luminescence in silica: from non-controlled impurity to germano-silicate core of telecommunication fiber preforms
2003
Abstract We have studed luminescence properties of doped silica with different concentrations of germanium. The basic luminescence parameters such as spectral dependencies, decay kinetics and polarization at different temperatures were measured. Three spectral ranges 3.5–5.5 eV(I), 5.5–7 eV(II), 7–8 eV(III) in the optical transparency range of silica could be chosen from these data. Range I possesses a weak variation of basic parameters of luminescence of the germanium related oxygen deficient center with the change of luminescence center concentration from extremely low in pure silica to the germano-silica core of optical telecommunication fiber preforms. The temperature dependence of lumi…
Photostimulable energy transfer in doped nanostructures of alkali halides
1998
Abstract In nanostructures of doped alkali halides, unrelaxed H-centres produced in the exciton decay are able to escape from the surface thus producing in the grains of polycrystalline film an excess concentration of F-centres, which has a great tendency to form an interacting F-centre chain or a canal. Role of this F-centre chain in photostimulable energy transfer is analysed. It is concluded that specific interaction of unrelaxed H-centres and electrons with the F-centre chain (or the canal) leads to the temperature-independent exciton or electron transport at any distance. Hence, the temperatureindependent photostimulated luminescence (PSL) response production and retrieval are experime…
Continuous-Flow Synthesis of Orange Emitting Sn(II)-Doped CsBr Materials
2021
An ongoing demand toward lead-free all-inorganic cesium metal halide perovskites has presented Sn(II) as an ideal substitute of Pb(II) for applications in optoelectronic devices. The major concern regarding Sn(II) is the instability due to the ambient oxidation to Sn(IV). To expand the scope of traditional perovskite and analogues, herein the synthesis and optical performance of Sn(II)-doped CsBr, a new material formed by interstitial doping of Sn(II) into the CsBr matrix, are reported for the first time. This material is prepared following an antisolvent mediated recrystallization method using a continuous flow reactor, which is beneficial for scaling up the production compared to traditio…
Infrared to visible upconversion luminescence properties in the system Ln2BaZnO5 (Ln=La, Gd)
2009
Abstract We have investigated the upconversion properties of the rare-earth doped systems La 2 BaZnO 5 ( I 4/ mcm ) and Gd 2 BaZnO 5 ( Pbnm ). The dependence of the luminescence properties on the identity and the concentration of the dopants, Er 3+ and Er 3+ co-doped with Yb 3+ , as well as on the synthetic route, was examined. Following coherent excitation at 975 nm, strong upconversion emission was observed in the visible region (525, 550 and 660 nm). Power dependence studies revealed a two photon process for these emissions. In the co-doped samples, a blue emission (410 nm) could also be observed. For this emission, the power dependence studies confirmed a three photon process.
Is unintentional doping real, or just an excuse?
2017
Although some athletes who engage in doping do so willingly in order to gain an unfair advantage (ie, ‘to cheat’), the possibility of athletes doping inadvertently or unintentionally cannot be discounted. In this article, we aim to address common misconceptions of the notion of ‘unintentional doping’, and discuss this topic with reference to statistics, reports and recommendations (eg, anti-doping codes) produced by the World Anti-Doping Agency (WADA), together with evidence from recent empirical research. Unintentional doping (also known as ‘inadvertent’ or ‘accidental’ doping) refers to the accidental consumption of performance-enhancing substances included on WADA’s banned list.1 It ofte…
Transport properties of silicon doped n-indium selenide
1992
Hall effect and resistivity measurements in silicon doped indium selenide (InSe), from 7K to 500K, are reported. Results are interpreted through a model, previously proposed for tin doped InSe, that takes into account the contribution of both three- and two-dimensional electrons to charge transport along the layers in InSe.