Enhancement of luminescence quantum yield of 1.5 µm emission from Er-doped SiO2 sensitized with Si nanocrystals

2014 ◽  
Vol 1592 ◽  
Author(s):  
S. Saeed ◽  
T. Gregorkiewicz
Keyword(s):  
Quantum Yield ◽  
Threshold Energy ◽  
Threshold Value ◽  
High Energy ◽  
Excitation Energies ◽  
Si Nanocrystals ◽  
Incoming Photon ◽  
Photon Conversion ◽  
Sample Characteristics ◽  
Er Doped

ABSTRACTExcitation of multiple Er3+ ions upon absorption of a single high-energy photon increases Er-related emission at 1.5 μm, and therefore enhances UV/visible-to-IR photon conversion efficiency. Here we investigate this effect for layers of Er-doped SiO2 sensitized with silicon nanocrystals by measuring the quantum yield of 1.5 µm Er-related emission. We demonstrate dramatic increase of the emission commencing for excitation energies above a certain threshold value, as the number of Er3+ ions excited upon absorption of a single incoming photon increases. By comparing differently prepared materials, we show that the actual value of this threshold energy and the rate of the observed increase of the quantum yield depend on sample characteristics – the size of Si nanocrystals and the ratio of Er3+ ions and nanocrystals concentrations.

Anisotropy of damage productions in electron irradiated molybdenum

1978 ◽  
Vol 36 (1) ◽  
pp. 354-355
Author(s):  
K. Izui ◽  
S. Furuno ◽  
H. Otsu ◽  
T. Nishida ◽  
H. Maeta
Keyword(s):  
Electron Flux ◽  
Threshold Energy ◽  
High Energy ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
Displacement Threshold ◽  
The Mean ◽  
Channeling Effect ◽  
Different Origins ◽  
Threshold Energies

Anisotropy of damage productions in crystals due to high energy electron bombardment are caused from two different origins. One is an anisotropic displacement threshold energy, and the other is an anisotropic distribution of electron flux near the atomic rows in crystals due to the electron channeling effect. By the n-beam dynamical calculations for germanium and molybdenum we have shown that electron flux at the atomic positions are from ∽4 to ∽7 times larger than the mean incident flux for the principal zone axis directions of incident 1 MeV electron beams, and concluded that such a locally increased electron flux results in an enhanced damage production. The present paper reports the experimental evidence for the enhanced damage production due to the locally increased electron flux and also the results of measurements of the displacement threshold energies for the <100>,<110> and <111> directions in molybdenum crystals by using a high voltage electron microscope.

In situ irradiation effects studies in medium- and high-voltage TEM

1995 ◽  
Vol 53 ◽  
pp. 234-235
Author(s):  
Charles W. Allen
Keyword(s):  
Cross Section ◽  
Particle Flux ◽  
Threshold Value ◽  
High Energy ◽  
Irradiation Damage ◽  
Defect Complexes ◽  
Lattice Position ◽  
Electrons And Ions ◽  
The Masses

With respect to structural consequences within a material, energetic electrons, above a threshold value of energy characteristic of a particular material, produce vacancy-interstial pairs (Frenkel pairs) by displacement of individual atoms, as illustrated for several materials in Table 1. Ion projectiles produce cascades of Frenkel pairs. Such displacement cascades result from high energy primary knock-on atoms which produce many secondary defects. These defects rearrange to form a variety of defect complexes on the time scale of tens of picoseconds following the primary displacement. A convenient measure of the extent of irradiation damage, both for electrons and ions, is the number of displacements per atom (dpa). 1 dpa means, on average, each atom in the irradiated region of material has been displaced once from its original lattice position. Displacement rate (dpa/s) is proportional to particle flux (cm-2s-1), the proportionality factor being the “displacement cross-section” σD (cm2). The cross-section σD depends mainly on the masses of target and projectile and on the kinetic energy of the projectile particle.

scholarly journals Monte Carlo Modeling and Design of Photon Energy Attenuation Layers for >10× Quantum Yield Enhancement in Si-Based Hard X-ray Detectors

Instruments ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 17
Author(s):  
Eldred Lee ◽  
Kaitlin M. Anagnost ◽  
Zhehui Wang ◽  
Michael R. James ◽  
Eric R. Fossum ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Quantum Yield ◽  
Photon Energy ◽  
High Efficiency ◽  
High Energy ◽  
Yield Enhancement ◽  
X Ray ◽  
Simulation Results ◽  
Conversion Efficiencies

High-energy (>20 keV) X-ray photon detection at high quantum yield, high spatial resolution, and short response time has long been an important area of study in physics. Scintillation is a prevalent method but limited in various ways. Directly detecting high-energy X-ray photons has been a challenge to this day, mainly due to low photon-to-photoelectron conversion efficiencies. Commercially available state-of-the-art Si direct detection products such as the Si charge-coupled device (CCD) are inefficient for >10 keV photons. Here, we present Monte Carlo simulation results and analyses to introduce a highly effective yet simple high-energy X-ray detection concept with significantly enhanced photon-to-electron conversion efficiencies composed of two layers: a top high-Z photon energy attenuation layer (PAL) and a bottom Si detector. We use the principle of photon energy down conversion, where high-energy X-ray photon energies are attenuated down to ≤10 keV via inelastic scattering suitable for efficient photoelectric absorption by Si. Our Monte Carlo simulation results demonstrate that a 10–30× increase in quantum yield can be achieved using PbTe PAL on Si, potentially advancing high-resolution, high-efficiency X-ray detection using PAL-enhanced Si CMOS image sensors.

Enhanced emission of Er3+ from alternately Er doped Si-rich Al2O3 multilayer film with Si nanocrystals as broadband sensitizers

2012 ◽  
Vol 258 (6) ◽  
pp. 1896-1901 ◽  
Author(s):  
Xiao Wang ◽  
Zuimin Jiang ◽  
Fei Xu ◽  
Zhongquan Ma ◽  
Run Xu ◽  
...  
Keyword(s):  
Multilayer Film ◽  
Si Nanocrystals ◽  
Er Doped

Coupling and Cooperative Up-conversion Coefficients in Er-doped Si Nanocrystals

2003 ◽  
Vol 770 ◽  
Author(s):  
Domenico Pacifici ◽  
Giorgia Franzò ◽  
Fabio Iacona ◽  
Francesco Priolo
Keyword(s):  
Steady State ◽  
Energy Level ◽  
Energy Level Scheme ◽  
Time Resolved ◽  
A Value ◽  
Si Nanocrystals ◽  
Si Nanocrystal ◽  
Conversion Coefficients ◽  
Quantitative Understanding ◽  
Er Doped

AbstractIn the present work, a quantitative understanding of the Er-doped Si nanocrystals interaction is reported. We present a model based on an energy level scheme taking into account the coupling between each Si nanocrystal and the neighboring Er ions. By fitting the steady state and time resolved luminescence signals at both the 1.54 and 0.98 μm Er lines we were able to determine a value of 3×10-15 cm3 s-1 for the coupling coefficient. Moreover, a strong cooperative up-conversion mechanism, active between two excited Er ions and characterized by a coefficient of 7×10-17 cm3 s-1, will be shown to be active in the system, demonstrating that each Si nanocrystal can actually excite more than one Er ion.

scholarly journals Resonant Ultrarelativistic Electron–Positron Pair Production by High-Energy Electrons in the Field of an X-ray Pulsar

Universe ◽  
2020 ◽  
Vol 6 (9) ◽  
pp. 132 ◽  
Author(s):  
Georgii K. Sizykh ◽  
Sergei P. Roshchupkin ◽  
Victor V. Dubov
Keyword(s):  
Pair Production ◽  
Threshold Energy ◽  
Structure Constant ◽  
High Energy ◽  
Differential Probability ◽  
X Ray ◽  
Initial Electron ◽  
Ultrarelativistic Electron ◽  
Electron Positron ◽  
Electron Positron Pair

The process of resonant high-energy electron–positron pair production by an ultrarelativistic electron colliding with the field of an X-ray pulsar is theoretically investigated. Resonant kinematics of the process is studied in detail. Under the resonance condition, the intermediate virtual photon in the X-ray pulsar field becomes a real particle. As a result, the initial process of the second order in the fine structure constant effectively reduces into two successive processes of the first order: X-ray-stimulated Compton effect and X-ray-stimulated Breit–Wheeler process. For a high-energy initial electron all the final ultrarelativistic particles propagate in a narrow cone along the direction of the initial electron momentum. The presence of threshold energy for the initial electron which is of order of 100 MeV for 1-KeV-frequency field is shown. At the same time, the energy spectrum of the final particles (two electrons and a positron) highly depends on their exit angles and on the initial electron energy. This result significantly distinguishes the resonant process from the non-resonant one. It is shown that the resonant differential probability significantly exceeds the non-resonant one.

Structural and Optical Properties of Rare-Earth Doped Lithium Niobate Waveguides Formed by Mev Helium Implantation

1995 ◽  
Vol 396 ◽  
Author(s):  
B. Herreros ◽  
G. Lifante ◽  
F. CussÓ ◽  
A. Kling ◽  
J.C. Soares ◽  
...  
Keyword(s):  
Lithium Niobate ◽  
Rare Earths ◽  
Optical Waveguides ◽  
Bulk Material ◽  
High Energy ◽  
Structural And Optical Properties ◽  
Lattice Damage ◽  
Helium Implantation ◽  
Er Doped ◽  
Rare Earth Doped

AbstractResults of investigations of optical waveguides formed by high energy helium implantation into lithium niobate codoped with 5 mol% MgO and 1 mol% Tm3+ or 1 mol% Er3+ are reported. A comparative study of structural and luminescence properties between implanted and untreated samples has been performed by means of Rutherford backscattering (RBS) combined with channeling and photoluminescence methods, respectively in order to investigate residual lattice damage and the incorporation of the optical active rare earths. For the case of Tm a full substitutional incorporation on the lithium site and a high crystal quality in both bulk and implanted waveguide material has been found. For Er doped lithium niobate the channeling results show a fraction of Er randomly incorporated or forming precipitates and a deterioration of the waveguide's lattice. The optical investigations show in both cases only a slight broadening of the emission lines of the rare earths in the waveguides compared to the bulk material.

Role of the energy transfer in the optical properties of undoped and Er-doped interacting Si nanocrystals

2001 ◽  
Vol 89 (1) ◽  
pp. 264-272 ◽  
Author(s):  
Francesco Priolo ◽  
Giorgia Franzò ◽  
Domenico Pacifici ◽  
Vincenzo Vinciguerra ◽  
Fabio Iacona ◽  
...  
Keyword(s):  
Optical Properties ◽  
Energy Transfer ◽  
Si Nanocrystals ◽  
Er Doped
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