Search results for "doping"
showing 10 items of 801 documents
Cerium-Doped Copper(II) Oxide Hollow Nanostructures as Efficient and Tunable Sensors for Volatile Organic Compounds
2018
Tuning sensing capabilities of simple to complex oxides for achieving enhanced sensitivity and selectivity toward the detection of toxic volatile organic compounds (VOCs) is extremely important and remains a challenge. In the present work, we report the synthesis of pristine and Ce-doped CuO hollow nanostructures, which have much higher VOC sensing and response characteristics than their solid analogues. Undoped CuO hollow nanostructures exhibit high response for sensing of acetone as compared to commercial CuO nanoparticles. As a result of doping with cerium, the material starts showing selectivity. CuO hollow structures doped with 5 at. % of Ce return highest response toward methanol sens…
Structural and Electrical Transport Properties of Si doped GaN nanowires
2016
The control and assessment of doping in GaN nanostructures are crucial for the realization of GaN based nanodevices. In this study, we have investigated a series of Si-doped GaN nanowires (NWs) grown by molecular beam epitaxy (MBE) with a typical dimension of 2–3 µm in length, and 20–200 nm in radius. In particular, high resolution energy dispersive X-ray spectroscopy (EDX) has illustrated a higher Si incorporation in NWs than that in two-dimensional (2D) layers and Si segregation at the edge of the NW with the highest doping. Moreover, direct transport measurements on single NWs have revealed a controlled doping with resistivity from 2 × 10−2 to 10−3 Ω.cm for Si doped NWs. Field effect tra…
Nanosensor Systems Simulations
2017
The chapter presents functionalized CNT and GNR nanostructures as the basis for the creation of physical, chemical and biochemical nanosensors. We have shown in our simulations the sensitivity of electron conductivity of FET-type nanodevices (based on CNTs and GNRs) to local doping by nitrogen and boron. This phenomenon provides the prospective of creating nanosensors.
Mg and In Codoped p-type AlN Nanowires for pn Junction Realization.
2019
Efficient, mercury-free deep ultraviolet (DUV) light-emitting diodes (LEDs) are becoming a crucial challenge for many applications such as water purification. For decades, the poor p-type doping and difficult current injection of Al-rich AlGaN-based DUV LEDs have limited their efficiency and therefore their use. We present here the significant increase in AlN p-doping thanks to Mg/In codoping, which leads to an order of magnitude higher Mg solubility limit in AlN nanowires (NWs). Optimal electrical activation of acceptor impurities has been further achieved by electron irradiation, resulting in tunnel conduction through the AlN NW p-n junction. The proposed theoretical scenario to account f…
Overview of radiation induced point defects in silica-based optical fibers
2019
International audience; Silica-based optical fibers, fiber-based devices and optical fiber sensors are today integrated in a variety of harsh environments associated with radiation constraints. Under irradiation, the macroscopic properties of the optical fibers are modified through three main basic mechanisms: the radiation induced attenuation, the radiation induced emission and the radiation induced refractive index change. Depending on the fiber profile of use, these phenomena differently contribute to the degradation of the fiber performances and then have to be either mitigated for radiation tolerant systems or exploited to design radiation detectors and dosimeters. Considering the stro…
Characterization of optogeometric parameters of optical fibers by near-field scanning probe microscopies
2000
The combination of atomic-force and scanning-near-field optical microscopies is useful for characterizing the physical and optical parameters of optoelectronic devices. With a commercial atomic-force microscope adapted to perform scanning-near-field optical measurements, we succeed in determining core diameters, localizing the erbium doping zone, and analyzing propagation modes in erbium-doped and multimodal optical fibers.
First-principles calculations of point defects in inorganic nanotubes
2013
The first-principles calculations have been performed to investigate the ground-state properties of monoperiodic boron nitride (BN), TiO2, and SrTiO3 single-walled nanotubes (SW NTs) containing extrinsic point defects. The hybrid exchange–correlation functionals PBE, B3LYP, and B3PW within the framework of density functional theory (DFT) have been applied for large-scale ab initio calculations on NTs with the following substitutional impurities: AlB, PN, GaB, AsN, InB, and SbN in the BN NT, as well as CO, NO, SO, and FeTi in the TiO2 and SrTiO3 NTs, respectively. The variations in formation energies obtained for equilibrium defective nanostructures allow us to predict the most stable compos…
Upconversion luminescence in erbium doped transparent oxyfluoride glass ceramics containing hexagonal NaYF4 nanocrystals
2015
Abstract In this work transparent erbium doped oxyfluoride glass ceramics containing hexagonal NaYF 4 nanocrystals has been prepared by melt-quenching and subsequent heat treatment of the precursor glass. The formation of β-NaYF 4 was confirmed by X-ray diffraction measurements. The overall intensity of the upconversion luminescence of the glass ceramics sample is 2 orders of magnitude higher than that of the precursor glass. The observed enhancement of the efficiency is explained by the incorporation of Er 3+ into low-phonon β-NaYF 4 crystalline phase.
Selective excitation of up-conversion luminescence by Yb3+–Er3+ energy transfer in glass and crystalline phase of oxyfluoride glass ceramics
2010
Up-conversion luminescence of oxyfluoride glass and glass ceramics containing LaF3 crystallites doped with Yb 3+ and Er 3+ was investigated at low temperature. Excitation of Yb 3+ in the IR region revealed the fast and the slow components of Er 3+ up-conversion luminescence originating from both glass and crystalline phases. The temporal differences of the both kinds of the luminescence allowed reconstructing the excitation spectra of the up-conversion luminescence related to the glass and crystalline phases in the glass ceramics. 2010 Elsevier B.V. All rights reserved.
Time-resolved cathodoluminescence spectroscopy of YAG and YAG:Ce3+ phosphors
2019
Abstract The phosphor powders, both undoped and Ce3+ doped with different concentration Y3Al5O12 (YAG), were synthesized by the solid-state reaction method with addition of BaF2 flux. SEM and XRD characterization of the samples were performed. The spectral and luminescence decay kinetic characteristics under the electron beam irradiation with nano- and picoseconds pulse duration and the electron energies of 250 keV and 55 keV were studied, respectively. Two bands in the cathodoluminescence spectrum of YAG:Ce3+ phosphors were observed with maxima at 2.19 ± 0.05 and 2.4 eV. The intensity ratio of these two bands depends on the electron energy and the duration of the excitation pulse. Instead,…