Variations in the Photoluminescence Intensity of Chemically and Anodically Etched Silicon Films

1993 ◽  
Vol 298 ◽  
Author(s):  
P.S Williams ◽  
J.N. Kidder ◽  
H. Yun ◽  
D. Crain ◽  
T.P. Pearsall
Keyword(s):  
Luminescent Properties ◽  
Silicon Films ◽  
Photoluminescence Intensity ◽  
Ambient Conditions ◽  
X Ray ◽  
Initial Characterization ◽  
Etched Silicon ◽  
Free Films

AbstractWe are studying the effects of etch conditions on the surface morphology, chemistry, and luminescent properties of porous silicon (PS) films. Luminescent silicon films are produced by chemical etching using solutions of HNO3 in HF and by anodic etching using aqueous HF electrolytes. Films produced by both methods are analyzed and compared using photoluminescence (PL), vibrational, and X-ray photoelectron (XPS) spectroscopies. The initial characterization of PS is performed immediately following the etching process, resulting in oxide-free films (as confirmed by XPS). In chemically etched PS films, the luminescent intensity decreases as the vol. % HNO3 in etch solution increases. Spectral features evolve in the PL spectrum of chemically etched films as the result of aging under ambient conditions and when the films are cooled under illumination. Moreover, we have also found that increased electrolyte convection results in a decrease in photoluminescence intensity of PS films formed anodically. The role of electrolyte flow in modifying the luminescent properties of PS is being evaluated in an etch cell with well-characterized hydrodynamics.

Synthesis and Characterization of Luminescent Properties of NaGdF4 Phosphors

2013 ◽  
Vol 423-426 ◽  
pp. 430-434
Author(s):  
Chang Lin Li ◽  
Tian Li ◽  
Jing Liu ◽  
Xin Ze Wang ◽  
Hong Jian Gao ◽  
...  
Keyword(s):  
Solvothermal Method ◽  
Luminescent Properties ◽  
High Energy ◽  
Luminescence Spectra ◽  
Photoluminescence Intensity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Light Excitation ◽  
Energy Ball

β-NaGdF4: Yb, Tm/β-NaGdF4: Eu and β-NaGdF4: Yb, Tm, Eu particles were successfully synthesized by two different methods, solvothermal method and high-energy ball milling. The properties were measured by X-ray diffraction (XRD), TEM and luminescence spectra. All samples shown the strong photoluminescence intensity under 980 nm light excitation and emission of Eu3+ was observed. Finally, two methods are compared in paper.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

scholarly journals Appearance of efficient luminescence energy transfer in doped orthovanadate nanocrystals

2017 ◽  
Vol 50 (3) ◽  
pp. 787-794 ◽  
Author(s):  
Swati Bishnoi ◽  
G. Swati ◽  
Paramjeet Singh ◽  
V. V. Jaiswal ◽  
Mukesh K. Sahu ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Band Gap ◽  
Photoluminescence Intensity ◽  
X Ray Diffraction ◽  
Synthesis Mechanism ◽  
Enhanced Photoluminescence ◽  
Nir Absorption ◽  
Decay Parameters

This paper reports the detailed synthesis mechanism and the structural, morphological and optical characterization of ultraviolet (∼311 nm) excitable samarium doped gadolinium yttrium orthovanadate, (Gd,Y)VO4:Sm3+, nanocrystals. X-ray diffraction and Rietveld refinement studies confirmed that the synthesized samples crystallize in a tetragonal structure withI41/amdspace group. The enhanced photoluminescence intensity of (Gd,Y)VO4:Sm3+compared with the existing YVO4:Sm3+phosphor clearly indicates the significant role of Gd3+ions. This has been attributed to the sensitization of the6PJenergy level of Gd3+ions by energy transfer from orthovanadate (VO43−) ions and subsequent energy trapping by Sm3+ions. The energy transfer from VO43−to Sm3+viaGd3+ions as intermediates and concentration quenching of Gd3+luminescence are discussed in detail. The optical band gap of the as-prepared nanocrystals has been estimated using UV–vis–NIR absorption spectroscopy, which reveals a slightly higher band gap (3.75 eV) for YVO4as compared to GdYVO4(3.50 eV). Furthermore, confocal microcopy, decay parameters and Commission Internationale de l'Eclairage chromatic coordinates have supplemented these studies, which established the suitability of these nanophosphors for achieving spectral conversion in silicon solar cells.

scholarly journals Different Roles of Ce3+ Optical Centers in Oxyorthosilicate Nanocrystals at X-ray and UV Excitation

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 114 ◽  
Author(s):  
Vladyslav Seminko ◽  
Pavel Maksimchuk ◽  
Iryna Bespalova ◽  
Yuri Malyukin
Keyword(s):  
Crystal Structure ◽  
Dominant Role ◽  
Luminescence Spectra ◽  
Photoluminescence Intensity ◽  
Bulk Crystals ◽  
Space Group ◽  
X Ray ◽  
Oxygen Coordination ◽  
Cation Sites

Luminescence properties of Lu2SiO5:Ce3+ and Y2SiO5:Ce3+ nanocrystals were studied using photo- and X-ray luminescence techniques. The crystal structure of Re2SiO5 nanocrystals (P21/c space group) differs from the crystal structure of Re2SiO5 bulk crystals (C2/c space group) with 9- and 7-oxygen-coordinated cation positions instead of 6- and 7-coordinated ones observed for Re2SiO5 bulk crystals. Two optical centers (Ce1 and Ce2) were observed for Re2SiO5:Ce3+ nanocrystals originating from cerium ions substituting 9- and 7-oxygen-coordinated cation sites. Preferential substitution of larger cation sites by cerium ions leads to higher photoluminescence intensity of Ce1 centers, however, Ce2 centers are the main centers for electron-hole recombination, so only Ce2 band is observed in X-ray luminescence spectra. The features of oxygen coordination of Ce1 and Ce2 centers and high content of oxygen vacancies in Re2SiO5:Ce3+ nanocrystals can provide preferential trapping of electrons near Ce2 centers, and therefore, the dominant role of Ce2 band in X-ray luminescence spectra.

scholarly journals Radio-, Thermo- and Photoluminescence Properties of Lu2O3:Eu and Lu2O3:Tb Nanopowder and Film Scintillators

Crystals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 148 ◽  
Author(s):  
P. Popielarski ◽  
J. Zeler ◽  
P. Bolek ◽  
T. Zorenko ◽  
K. Paprocki ◽  
...  
Keyword(s):  
Spin Coating ◽  
Luminescent Properties ◽  
Emission Lines ◽  
Hydrothermal Processing ◽  
Photoluminescence Properties ◽  
Temperature Quenching ◽  
X Ray ◽  
Decay Times ◽  
Coating Method

This work is dedicated to the preparation and characterization of the radio-, thermo-, and photoluminescent properties of Lu2O3:Eu and Lu2O3:Tb nanopowder (NPs) scintillators, prepared by means of hydrothermal processing, and their film analogues made of these NPs by the spin coating method. The luminescent properties of NPs and films were characterized by cathodoluminescence (CL), photoluminescence (PL), X-ray excited radioluminescence (RL), and thermoluminescence (TL) at low and high temperatures. In Lu2O3:Eu NPs and films, mostly the luminescence of Eu3+ ions occupying the C2 site of the host, with the most intensive peaks at 611.6 nm and a decay time of 1.5 ms, was observed. On the contrary, two types of Tb3+ centers in the C2 and C3i sites with the main emission lines at 542.4 and 544.0 nm and the corresponding 4f→5d excitation bands at 270 and 305 nm and decay times of t1/e = 2.17 and 3.96 ms were observed in the case of Lu2O3:Tb NPs and films. Indications were noted that Tb3+ in the C3i symmetry position was most active in the CL spectra of Lu2O3:Tb NPs and a respective film. Thermoluminescent peaks at 110 °C and 170 °C for Lu2O3:Eu NPs and at 75 °C and 120 °C in Lu2O3:Tb NPs were observed corresponding to the hole and electron traps, respectively. Significantly different onsets of temperature quenching of Eu3+ and Tb3+ luminescence in Lu2O3:Eu and Lu2O3:Tb NPs were found at ~90 °C and ~320 °C, respectively.

scholarly journals Material Characterization of Magnetorheological Elastomers with Corroded Carbonyl Iron Particles: Morphological Images and Field-dependent Viscoelastic Properties

2019 ◽  
Vol 20 (13) ◽  
pp. 3311 ◽  
Author(s):  
Siti Aishah Binti Abdul Aziz ◽  
Saiful Amri Mazlan ◽  
Nur Azmah Nordin ◽  
Nor Azlin Nazira Abd Rahman ◽  
U Ubaidillah ◽  
...  
Keyword(s):  
Carbonyl Iron ◽  
Matrix Material ◽  
Rheological Characteristics ◽  
Iron Particles ◽  
Ambient Conditions ◽  
X Ray ◽  
Field Dependent ◽  
Mr Effect

High temperatures and humidity could alter the field-dependent rheological properties of MR materials. These environmental phenomena may accelerate the deterioration processes that will affect the long-term rheological reliability of MR materials such as MR elastomer (MRE). This study therefore attempts to investigate the field-dependent rheological characteristics of MRE with corroded carbonyl iron particles (CIPs). The corroded CIPs were treated with hydrochloric acid (HCl) as a way of providing realistic environments in gauging the CIPs reaction towards the ambient conditions. The corroded CIPs along with silicone rubber as a matrix material were used in the fabrication of the MRE samples. To observe the effect of HCl treatment on the CIPs, the morphological observations of MREs with non-corroded and corroded CIPs were investigated via field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDX) and x-ray diffractometer (XRD). In addition, the magnetic properties were examined through the vibrating sample magnetometer (VSM), while the field-dependent rheological characteristics such as the storage modulus of MRE with the corroded CIPs were also tested and compared with the non-corroded CIPs. The results showed that the corroded CIPs possessed hydrangea-like structures. In the meantime, it was identified that a sudden reduction of up to 114% of the field-dependent MR effect of MRE with the corroded CIPs was observed as a result of the weakened interfacial bonding between the CIPs and the silicon in the outer layers of the CIPs structure.

scholarly journals The Role of Percent Volume Buried in the Characterization of Copper(I) Complexes for Lighting Purposes

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2647 ◽  
Author(s):  
Murat Alkan-Zambada ◽  
Edwin C. Constable ◽  
Catherine E. Housecroft
Keyword(s):  
Solid State ◽  
Single Crystal ◽  
Quantum Yields ◽  
X Ray ◽  
Photophysical Behavior

The usefulness of percent volume buried (%Vbur) as a readily quantifiable property is investigated with regard to [Cu(NN)(PP)]+ complexes of interest for lighting purposes. Photoluminescence quantum yields (PLQYs) and single crystal X-ray structures of 100 reported compounds were assembled, %Vbur of the ligand systems were calculated and analyzed for correlations. We found that increased shielding of the central Cu(I) cation relying on shared contributions of both (NN) and (PP) ligand systems led to increased PLQYs. These findings are of relevance for future characterizations of Cu(I)-based complexes and their photophysical behavior in the solid-state.

scholarly journals Synthesis and Characterization of Strontium Titanate Nanoparticles as Potential High Temperature Oxygen Sensor Material

2006 ◽  
Vol 2006 ◽  
pp. 1-6 ◽  
Author(s):  
Florian Voigts ◽  
Tanja Damjanovic ◽  
Günter Borchardt ◽  
Christos Argirusis ◽  
Wolfgang Maus-Friedrichs
Keyword(s):  
High Temperature ◽  
Strontium Titanate ◽  
Photoelectron Spectroscopy ◽  
Oxygen Sensor ◽  
Ambient Conditions ◽  
X Ray ◽  
Sensor Material ◽  
Force Microscopy ◽  
Atomic Force

We present a simple and highly reproductive method for the preparation of thin films consisting of strontium titanate nanoparticles. The films are produced by spin coating of a sol on silicon targets and subsequent annealing under ambient conditions. Analysis by atomic force microscopy shows particles with typical sizes between 10 nm and 50 nm. X-ray photoelectron spectroscopy displays a stoichiometry of the films as anticipated from preliminary experiments with strontium titanate single crystals. Metastable-induced electron spectroscopy and ultraviolet photoelectron spectroscopy are used as tools to give evidence to the similar electronic properties of nanoparticle film and single crystal. These results support the prospect for an application of the nanoparticle films as high temperature oxygen sensor with superior properties.

Sign in / Sign up

Export Citation Format

Share Document