Excitation Wavelength and Saturation Effects on Gallium Nitride Photoluminescence

1995 ◽  
Vol 395 ◽  
Author(s):  
Mike Banas ◽  
Guangtian Liu ◽  
Jeff Ramer ◽  
Kang Zheng ◽  
Steve Hersee ◽  
...  
Keyword(s):  
Room Temperature ◽  
Broad Peak ◽  
Yellow Emission ◽  
Excitation Wavelength ◽  
Power Dependence ◽  
Neutral Donor ◽  
Photoluminescence Excitation Spectrum ◽  
Key Species ◽  
Saturation Effects ◽  
Excitation Model

ABSTRACTWe report on the excitation wavelength and power dependence of LPMOCVD grown GaN photoluminescence (PL). A mode-locked Ti:Sapphire laser that is doubled to provide a tunable wavelength range of 350-500 nm is used to pump the GaN samples. Special attention has been paid to the “yellow” (∼567 nm) luminescence. Different power dependence characteristics of the yellow emission are observed when pumping above and below the bandgap. A measurement of the photoluminescence excitation spectrum of the yellow peak (∼567 nm) is also performed and this spectrum shows a peak at room temperature at 3.36 eV (369 nm), an additional broad peak at 77 K and only the broad peak at 7 K. An excitation model is used to explain the behavior of the yellow emission, suggesting the neutral donor serves as a key species for the yellow emission.

Preparation and Properties of La2O3-CaO-P2O5 Glasses Doped with Eu3+ Ions

2016 ◽  
Vol 675-676 ◽  
pp. 376-379 ◽  
Author(s):  
Narun Luewarasirikul ◽  
Piyachat Meejitpaisan ◽  
Jakrapong Kaewkhao
Keyword(s):  
Calcium Phosphate ◽  
Molar Volume ◽  
Absorption Spectra ◽  
Room Temperature ◽  
Emission Spectra ◽  
Phosphate Glasses ◽  
Excitation Wavelength ◽  
Melt Quenching ◽  
Volume Measurements ◽  
Doped Glasses

Lanthanum calcium phosphate glasses doped with Eu3+ ions in compositions 20La2O3:10CaO:(70-x)P2O5:xEu2O3 (where x = 0.05, 0.10, 0.50 and 1.50 mol%) were prepared by melt-quenching technique. The density and molar volume measurements were carried out at room temperature. The absorption spectra were investigated in the UV-Vis-NIR region from 200 to 2500 nm. The emission spectra of Eu3+-doped glasses centered at 590 nm (5D0→7F1), 612 nm (5D0→7F2), 652 nm (5D0→7F3) and 699 nm (5D0→7F4) have been observed with 393 nm excitation wavelength.

scholarly journals Synthesis of Cu and Ce co-doped ZnO nanoparticles: crystallographic, optical, molecular, morphological and magnetic studies

2017 ◽  
Vol 35 (2) ◽  
pp. 427-434 ◽  
Author(s):  
Mohit Rawat ◽  
Jasmeet Singh ◽  
Jagpreet Singh ◽  
Chamkaur Singh ◽  
Amritpal Singh ◽  
...  
Keyword(s):  
Room Temperature ◽  
Sol Gel ◽  
Research Work ◽  
Yellow Emission ◽  
Near Band Edge ◽  
Band Edge Emission ◽  
Ferromagnetic Behavior ◽  
Magnetic Studies ◽  
Transmission Electron Microscopy Analysis ◽  
Co Doped

Abstract In the present research work, crystallographic, optical, molecular, morphological and magnetic properties of Zn1-xCuxO (ZnCu) and Zn1-x-yCeyCuxO (ZnCeCu) nanoparticles have been investigated. Polyvinyl alcohol (PVA) coated ZnCu and ZnCeCu nanoparticles have been synthesized by chemical sol-gel method and thoroughly studied using various characterization techniques. X-ray diffraction pattern indicates the wurtzite structure of the synthesized ZnCu and ZnCeCu particles. Transmission electron microscopy analysis shows that the synthesized ZnCu and ZnCeCu particles are of spherical shape, having average sizes of 27 nm and 23 nm, respectively. The incorporation of Cu and Ce in the ZnO lattice has been confirmed through Fourier transform infrared spectroscopy. Room temperature photoluminescence spectra of the ZnO doped with Cu and co-doped Ce display two emission bands, predominant ultra-violet near-band edge emission at 409.9 nm (3 eV) and a weak green-yellow emission at 432.65 nm (2.27 eV). Room temperature magnetic study confirms the diamagnetic behavior of ZnCu and ferromagnetic behavior of ZnCeCu.

Intense Photoluminescence and Photoluminescence Enhancement of Silicon Nanocrystals by Ultraviolet Irradiation

2007 ◽  
Vol 31 ◽  
pp. 74-76 ◽  
Author(s):  
P.T. Huy ◽  
P.H. Duong
Keyword(s):  
Silicon Nanocrystals ◽  
Room Temperature ◽  
Laser Excitation ◽  
Uv Light ◽  
Irradiation Time ◽  
Excitation Wavelength ◽  
Nonradiative Recombination ◽  
Emission Yield ◽  
Recombination Centers ◽  
Pl Intensity

Photoluminescence (PL) from silicon nanocrystals deposited on top of silica-glass template and from silicon nanocrystals in nc_Si/SiO2 multilayer films were studied as a function of ultraviolet (UV) laser irradiation time in vacuum. Both the films exhibit intense visible PL at room temperature under laser excitation. It was found that upon prolong irradiation time using a He-Cd laser (325 nm) the PL intensity of the films was spectacularly enhanced. The process is reversible and does not happen with excitation wavelength longer than 400 nm. Upon introducing air into the measurement chamber, a rapid decrease of the PL intensity was recorded. This observation suggests that the UV light may lead to modification of nonradiative recombination centers in the films and thus improves the emission yield of silicon nanocrystals.

Investigation on the Preparation and Properties of Monodispersed Spherical Y2O3:Dy3+ Phosphor

2017 ◽  
Vol 726 ◽  
pp. 255-260 ◽  
Author(s):  
Jin Kai Li ◽  
Zhong Peng Liu ◽  
Jiang Fan Luo ◽  
Xin Bo Ma ◽  
Xin Teng ◽  
...  
Keyword(s):  
Blue Emission ◽  
Yellow Emission ◽  
Excitation Wavelength ◽  
Homogeneous Precipitation ◽  
Fluorescent Properties ◽  
Spherical Morphology ◽  
Rare Earth Nitrate ◽  
Urea Content ◽  
Phase Pure ◽  
Optimal Excitation

The oxide phosphor (Y1-xDyx)2O3(x=0-0.1) was obtained by calcining their respective precursors synthesized by homogeneous precipitation technique using rare earth nitrate as mother salt and urea as precipitating agent. The particle shape/size, fluorescent properties (especially the influence of Dy3+ concentration and calcination temperature) of the product was studied in detail. The results showed that the precursors exhibit monodisperse spherical morphology whose size can be controlled by adjusting the urea content. The phase pure (Y1-xDyx)2O3 can be obtained by calcining precursor at least 600 °C, and the monodisperse spherical morphology can be kept at even high temperature of 1000 °C. The (Y1-xDyx)2O3 phosphors exhibit strong yellow emission at ~577 nm (4F9/2→6H13/2 transition of Dy3+) and blue emission at ~491 nm (4F9/2→6H15/2 transition of Dy3+) upon optimal excitation wavelength of ~352 nm. The quenching concentration of Dy3+ was determined to be ~2 at% (x=0.02). The emission intensity of (Y1-xDyx)2O3 phosphors can be improved with the temperature and particle size increasing

Synthesis and Compositional Control of Size Monodisperse SixGe1-x Nanocrystals for Optoelectronic Applications

2013 ◽  
Vol 1551 ◽  
pp. 11-16
Author(s):  
Keith Linehan ◽  
Darragh Carolan ◽  
Daithi Ó Sé ◽  
Hugh Doyle
Keyword(s):  
Silicon Germanium ◽  
Quantum Confinement ◽  
Room Temperature ◽  
Blue Emission ◽  
Excitation Wavelength ◽  
Microscopy Imaging ◽  
Quantum Confinement Effects ◽  
Transmission Electron ◽  
Co Reduction ◽  
Compositional Control

ABSTRACTAlkyl-terminated SixG1-x nanocrystals are prepared at room temperature by co-reduction of Si and Ge precursors by hydride reducing agents within inverse micelles. Compositional control of the alloy silicon-germanium NCs (ca. 3.6 nm) is achieved by varying the relative amounts of each precursor used in the synthesis. Transmission electron microscopy imaging confirmed that the NCs are highly crystalline with a narrow size distribution; optical spectroscopy shows strong quantum confinement effects, with moderate absorption in the UV spectral range, and a strong blue emission with a marked dependency on excitation wavelength.

Optical Properties of Nd Doped Lead Borotellurite Glass

2016 ◽  
Vol 846 ◽  
pp. 193-198 ◽  
Author(s):  
Azman Kasim ◽  
H. Azhan ◽  
S. Akmal Syamsyir ◽  
Mardhiah Abdullah ◽  
M.R.S. Nasuha
Keyword(s):  
Optical Properties ◽  
Room Temperature ◽  
Optical Band Gap ◽  
Band Gap Energy ◽  
Rare Earth Ions ◽  
Band Gaps ◽  
Refractive Indices ◽  
Excitation Wavelength ◽  
Gap Energy ◽  
Trivalent Rare Earth

Many trivalent rare earth ions such as Er3+, Tm3+, Ho3+, Pr3+ and Nd3+ were doped as absorption and emission centers in glass hosts. In this work, lead borotellurite (PBT) glass doped with neodymium ion (Nd3+) has been prepared and characterized by mean of their optical properties. The UV-Vis measurement has been carried out in order to determine the optical band gap energy, reflective indices and the polarizability. Optical absorption spectra of the glass samples are recorded in the range 400–900 nm at room temperature From the result, there are six significant absorption peaks that corresponds to 525 nm, 584 nm, 683 nm, 747 nm, 805 nm and 878 nm wavelength have been observed with the most predominant peak to be used as excitation wavelength is found centered at 584 nm. The energy band gaps as well as the refractive indices were found to vary from 2.50eV to 2.59eV and from 1.89 to 1.96 with mol% of Nd content respectively. Meanwhile, the polarizability shows a similar trend of results to refractive indices as it varies from 5.56 x 10-24 cm3 to 5.63 x 10-24 cm3. These results will be discussed further in details.

Preparation and Luminescence Properties of the Nano- Composite Materials LaF3 - SiO2: Eu3+

2011 ◽  
Vol 335-336 ◽  
pp. 981-984
Author(s):  
Xi Gui Wang ◽  
Xiao Xian Wang
Keyword(s):  
Room Temperature ◽  
Annealing Temperature ◽  
Sol Gel ◽  
Excitation Wavelength ◽  
Nano Materials ◽  
Nano Composite ◽  
Optimal Doping ◽  
Cerium Fluoride ◽  
Mineral Structure ◽  
Optimum Annealing Temperature

Eu3+doped LaF3-SiO2nano-composite material were synthesized by sol-gel method at room temperature, and the structure and properties were characterized by XRD, TG-DTA, IR, excitation and emission spectrum. The structure indicated that the optimal doping formula for preparing nano-materials was La5Si95that transformed into a stable mineral structure of cerium fluoride, and mainly found Si-O-Si bonds when the temperature was above 500 °C. Luminous property researches showed that the optimum annealing temperature was 500 °C. The best excitation wavelength was 395 nm when the monitoring wavelength was 612 nm, and the optimal doping molar concentration of Eu3+was 0.35 mol %.

ESR study of activated carbon fibers: preliminary results

1993 ◽  
Vol 8 (9) ◽  
pp. 2282-2287 ◽  
Author(s):  
S.L. di Vittorio ◽  
A. Nakayama ◽  
T. Enoki ◽  
M.S. Dresselhaus ◽  
M. Endo ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Specific Surface ◽  
Carbon Fibers ◽  
Room Temperature ◽  
Broad Peak ◽  
Activated Carbon Fibers ◽  
Temperature Peak ◽  
Dangling Bond ◽  
Surface Areas ◽  
Spin Resonance

We have carried out Electron Spin Resonance (ESR) measurements on activated carbon fibers (ACF) with specific surface areas (SSA) of 3000 and 2000 m2/g. The ESR spectrum of ACF fibers in air is extremely broad (500 to 1000 Gauss), and the spin susceptibility decreases rapidly with decreasing specific surface area. Also measured was the ESR signal of the desorbed fibers in vacuum. As a result of desorption, the broad peak decreases slightly in intensity, and a narrow (≍65 Gauss at room temperature) peak appears. We report results on the temperature dependence of both peaks. The narrow peak is interpreted as due to spins associated with dangling bonds, whereas we attribute the broad peak to the conduction carrier spins which is broadened by the boundary scattering process (T1 contribution) and the dipolar broadening process (T2 contribution) associated with the dangling bond spins.

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