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in subjects: "Photoluminescence"

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Effects of Hydrogen in the Annealing Environment on Photoluminescence from Si Nanoparticles in SiO(2)

The role of hydrogen in enhancing the photoluminescence (PL) yield observed from Si nanocrystals embedded in SiO{sub 2} has been studied. SiO{sub 2} thermal oxides and bulk fused silica samples have been implanted with Si and subsequently annealed in various ambients including hydrogen or deuterium forming gases (Ar+4%H{sub 2} or Ar+4%D{sub 2}) or pure Ar. Results are presented for annealing at temperatures between 200 and 1100 C. Depth and concentration profiles of H and D at various stages of… more

Date: March 23, 1999

Creator: Barbour, J. C.; Budai, J. D.; Hembree, D. M.; Meldrum, A.; White, C. W. & Withrow, S. P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Photoluminescence Studies of Lateral Composition Modulated Short-Period AlAs/InAs Superlattices

We present low temperature photoluminescence data for a series of spontaneous lateral composition modulation in (AlAs){sub m}/(InAs){sub n} short period superlattices on InP with differing average lattice constants, i.e., varying global strain. The low temperature photoluminescence peak energies were found to be much lower than the corresponding energy expected for the equivalent In{sub x}Al{sub 1{minus}x}As alloy. The bandgap energy reductions are found to approach 500 meV and this reduction i… more

Date: January 4, 1999

Creator: Ahrenkiel, S. P.; Follstaedt, D. M.; Jones, E. D.; Lee, S. R.; Mascarenhas, A.; Mirecki-Millunchick, J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Accelerated degradation studies of MEH-PPV

MEH-PPV, which normally has a reddish color, is well known to show photobleaching problems. The photobleaching can be greatly accelerated by exposure to laser light while in air. For example, shining 457 mn light of relatively low intensity (0.06 W/cm{sup 2}) on the MEH-PPV causes the photoluminescence to decrease by a factor of two within a few seconds of exposure, and to show a nearly complete bleaching of the material within 30 minutes. The degradation rate is strongly influenced by laser po… more

Date: July 1, 1995

Creator: Radousky, H. B.; Madden, A. D.; Pakbaz, K.; Hagler, T. W.; Lee, H. W. H.; Lorenzana, H. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Microwave-Assisted Synthesis and Photophysical Properties of Poly-Imine Ambipolar Ligands and Their Rhenium(I) Carbonyl Complexes

The phenomenon luminescence rigidochromism has been reported since the 1970s in tricarbonyldiimine complexes with a general formula [R(CO)3LX] using conventional unipolar diimine ligands such as 2,2;-bipyridine or 1,10-phenanthroline as L, and halogens or simple solvents as X. As a major part of this dissertation, microwave-assisted synthesis, purification, characterization and detailed photoluminescence studies of the complex fac-[ReCl(CO)3L], 1, where L = 4-[4,6-bis(3,5-dimethyl-1H-pyrazol-1-… more

Date: August 2017

Creator: Salazar Garza, Gustavo Adolfo

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Characterizing Recombination in CdTe Solar Cells with Time-Resolved Photoluminescence: Preprint

Time-resolved photoluminescence (TRPL) computer simulations demonstrate that under certain experimental conditions it is possible to assess recombination in CdTe solar cells in spite of the junction. This is supported by experimental findings that open-circuit voltage (Voc) is dependent on lifetime in a manner consistent with device theory. Measurements on inverted structures show that the CdCl2 treatment significantly reduces recombination in the CdTe layer without S diffusion. However, S diff… more

Date: May 1, 2006

Creator: Metzger, W. K.; Romero, M. J.; Dippo, P. & Young, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Time-Resolved Photoluminescence and Photovoltaics

The time-resolved photoluminescence (TRPL) technique and its ability to characterize recombination in bulk photovoltaic semiconductor materials are reviewed. Results from a variety of materials and a few recent studies are summarized and compared.

Date: January 1, 2005

Creator: Metzger, W. K.; Ahrenkiel, R. K.; Dippo, P.; Geisz, J.; Wanlass, M. W. & Kurtz, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Isotopically controlled semiconductors

The following article is an edited transcript based on the Turnbull Lecture given by Eugene E. Haller at the 2005 Materials Research Society Fall Meeting in Boston on November 29, 2005. The David Turnbull Lectureship is awarded to recognize the career of a scientist who has made outstanding contributions to understanding materials phenomena and properties through research, writing, and lecturing, as exemplified by the life work of David Turnbull. Haller was named the 2005 David Turnbull Lecture… more

Date: June 19, 2006

Creator: Haller, Eugene E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Spectroscopic properties of colloidal indium phosphide quantum wires

Colloidal InP quantum wires are grown by the solution-liquid-solid (SLS) method, and passivated with the traditional quantum dots surfactants 1-hexadecylamine and tri-n-octylphosphine oxide. The size dependence of the band gaps in the wires are determined from the absorption spectra, and compared to other experimental results for InP quantum dots and wires, and to the predictions of theory. The photoluminescence behavior of the wires is also investigated. Efforts to enhance photoluminescence ef… more

Date: July 11, 2008

Creator: Wang, Lin-Wang; Wang, Fudong; Yu, Heng; Li, Jingbo; Hang, Qingling; Zemlyanov, Dmitry et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Effect of hydrostatic pressure on degradation of CdTe/CdMgTeheterostructures grown by molecular beam epitaxy on GaAs substrates

We have shown that external hydrostatic pressure leads to the creation of structural defects, mainly in the vicinity of the II-VI/GaAs interface in the CdTe/Cd{sub 1-x}Mg{sub x}Te heterostructures grown by the molecular beam epitaxy method on GaAs substrates. These defects propagating across the epilayer cause permanent damage to the samples from the point of view of their electrical properties. In contrast, photoluminescence spectra are only weakly influenced by pressure. Our results shed ligh… more

Date: April 18, 2001

Creator: Wasik, D.; Baj, M.; Siwiec-Matuszyk, J.; Gronkowski, J.; Jasinski, J. & Karczewski, G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The picosecond dynamics of electron-hole pairs in graded and homogeneous CdS{sub x}Se{sub 1-x} semiconductors

Wavelength and composition dependence of the time-resolved luminescence were examined. Effects of macroscopic composition gradient and microscopic alloy disorder on e{sup {minus}}-h{sup +} pair dynamics were probed. Materials with both increasing and decreasing S content with distance from the surface were examined, where 0{le} {times} {le}1 over the full range. In these graded materials, the band gap energy also varies with position. The graded semiconductor luminescence shows strong wavelengt… more

Date: May 1, 1995

Creator: Hane, J.K.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Aggregation quenching in thin films of meh-ppv studied by near-field scanning optical microscopy and spectroscopy

Aggregates in thin films of conjugated polymers form excimer states and significantly reduce the photo- and electroluminescence efficiency in devices produced from these materials. We have studied the aggregate formation in thin films of MEH-PPV by near-field scanning optical microscopy and spectroscopy. Local photoluminescence spectroscopy and photo-bleaching experiments have been used to show that thin films of MEH-PPV are homogeneously aggregated and do not form aggregated domains.

Date: April 11, 2000

Creator: Huser, T & Yan, M

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Al2O3 Scale Development on Iron Aluminides

The structure and phase of the Al{sub 2}O{sub 3} scale that forms on an Fe{sub 3}Al-based alloy (Fe-28Al-5Cr) (at %) was investigated by transmission electron microscopy (TEM) and photoluminescence spectroscopy (PL). Oxidation was performed at 900 C and 1000 C for up to 190 min. TEM revealed that single-layer scales were formed after short oxidation times. Electron diffraction was used to show that the scales are composed of nanoscale crystallites of the {theta}, {gamma}, and {alpha} phases of … more

Date: November 10, 2005

Creator: Zhang, Xiao-Feng; Thaidigsmann, Katja; Ager, Joel & Hou, Peggy Y.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Near-field photoluminescence spectroscopy of localized states in InGaAsN alloys.

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Date: December 11, 2001

Creator: Mintairov, A. M.; Blagnov, P. A.; Kosel, T.; Merz, J. L.; Ustinov, V. M.; Vlasov, A. S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Effects of annealing on self-assembled InAs quantum dots and wetting layer in GaAs matrix

Post-growth thermal annealing effects on InAs/GaAs quantum dots (QDs) near Stransky-Krastanow transformation were investigated. Self-assembled QDs of average size of about 10 nm were grown by metal-organic vapor phase epitaxy. The photoluminescence (PL) due to emission from QDs as well as two peaks due to emission from the strained InAs wetting layer (WL) were observed in as-grown samples. Bimodal structure of the WL PL was attributed to WL regions of different thickness. There was almost no di… more

Date: April 18, 2001

Creator: Jasinski, J.; Babinski, A.; Bozek, R.; Szepielow, A. & Baranowski, J. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Magnetic Field Induced Charged Exciton Studies in a GaAs/Al(0.3)Ga(0.7)As Single Heterojunction

The magnetophotoluminescence (MPL) behavior of a GaAs/Al<sub>0.3</sub>Ga<sub>0.7</sub>As single heterojunction has been investigated to 60T. We observed negatively charged singlet and triplet exciton states that are formed at high magnetic fields beyond the {nu}=l quantum Hall state. The variation of the charged exciton binding energies are in good agreement with theoretical predictions. The MPL transition intensities for these states showed intensity variations (maxima and minima) at the {nu}=… more

Date: May 25, 1999

Creator: Kim, Yongmin; Munteanu, F. M.; Perry, C. H.; Reno, J. L.; Rickel, D. G. & Simmons, J. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Back Contact Effects on the Electro-Optical Properties of CdTe/CdS Solar Cells

Studies of junction photoluminescence (PL) in CdTe/CdS solar cells reveal that back-contact application produces a dramatic qualitative change in the junction picosecond-PL spectrum. Prior to contact application, the spectrum has two peaks at energies of 1.501 eV and 1.457 eV, corresponding to recombination in regions of CdTeS alloy with 2% and 12% sulfur content, respectively. After contact application, the spectrum consists of a single broad peak at 1.48 eV. Previous studies have shown that t… more

Date: October 15, 1998

Creator: Levi, D. H.; Albin, D. S.; Gessert, T. A. (National Renewable Energy Laboratory) & Woods, L. M. (Department of Electrical Engineering, Colorado State University, Ft. Collins, CO)

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Photoluminescence studies of modulation doped coupled double quantum wells in magnetic fields

We have studied the photoluminescence spectra of a series of mudulation doped couple double quantum well structures in parallel and perpendicular magnetic fields to 62 tesla at 4K and 77K, for B{parallel}a, the spectra display distinct Landau level transitions which show anti-crossing with the e1-hh1 exciton. At high fields, the lowest conduction band-valence exciton approaches the extrapolated 0- 0 Landau level. About 25 Tesla, there is valence band mixing of the e1-lh1, e1-hh2, e1-hh1 transit… more

Date: September 1, 1996

Creator: Kim, Y.; Perry, C. H.; Simmons, J. A.; Klem, J. F.; Jones, E. D. & Rickel, D. G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Vacuum-Based Time-Resolved Photoluminescence Measurement System Provides New Capability (Fact Sheet)

New measurement capability measures semiconductor minority-carrier lifetimes in conditions that simulate thin-film photovoltaic manufacturing environments. National Renewable Energy Laboratory (NREL) scientists have developed a new capability for measuring time-resolved photoluminescence (TRPL) in controlled environments, including under high vacuum and at elevated temperatures. This system enables the simulation of conditions in a thin-film photovoltaic (PV) manufacturing line. NREL's work in … more

Date: November 1, 2011

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Transmission Electron Microscopy Study of InN Nanorods

InN nanorods were grown on a, c-, and r-plane of sapphire and also on Si (111) and GaN (0001) by non-catalytic, template-free hydride metal-organic vapor phase epitaxy and studied by transmission electron microscopy, electron energy loss (EELS) and photoluminescence (PL) at room temperature. These nanocrystals have different shapes and different faceting depending on the substrate used and their crystallographic orientation. EELS measurements have confirmed the high purity of these crystals. Th… more

Date: July 13, 2006

Creator: Liliental-Weber, Z.; Li, X.; Kryliouk, Olga; Park, H.J.; Mangum,J. & Anderson, T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Atomic Structure of Pyramidal Defects in GaN:Mg; Influence ofAnnealing

The atomic structure of the characteristic defects (Mg-rich hexagonal pyramids) in p-doped bulk and MOCVD GaN:Mg thin films grown with Ga polarity was determined at atomic resolution by direct reconstruction of the scattered electron wave in a transmission electron microscope. Small cavities were present inside the defects, confirmed also with positron annihilation. The inside walls of the cavities were covered by GaN of reverse polarity compared to the matrix. Defects in bulk GaN:Mg were almos… more

Date: October 3, 2005

Creator: Liliental-Weber, Z.; Tomaszewicz, T.; Zakharov, D.; O'Keefe, M.; Hautakangas, S.; Saarinen, K. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

"High Quantum Efficiency of Band-Edge Emission from ZnO Nanowires"

External quantum efficiency (EQE) of photoluminescence as high as 20 percent from isolated ZnO nanowires were measured at room temperature. The EQE was found to be highly dependent on photoexcitation density, which underscores the importance of uniform optical excitation during the EQE measurement. An integrating sphere coupled to a microscopic imaging system was used in this work, which enabled the EQE measurement on isolated ZnO nanowires. The EQE values obtained here are significantly higher… more

Date: December 1, 2010

Creator: Gargas, Daniel; Gao, Hanwei; Wang, Hungta & Peidong, Yang

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Ultraviolet photosulfidation of III-V compound semiconductors for electronic passivation

A new vacuum-compatible passivation technique for III-V compound semiconductors has been developed. Sulfur passivation of GaAs(100) is produced by ultraviolet photolytic deposition of a sulfide species from vapor phase elemental sulfur. Photoluminescence studies of the photosulfided GaAs reveal a degree of passivation greater than or equal to that produced by conventional (NH{sub 4}{sub 2}S) solution treatment. X-ray Photoelectron Spectroscopy has shown that the sulfur resides on the surface as… more

Date: October 1, 1993

Creator: Zavadil, K. R.; Ashby, C. I. H.; Howard, A. J. & Hammons, B. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Comparison of quantum confinement effects between quantum wires and dots

Dimensionality is an important factor to govern the electronic structures of semiconductor nanocrystals. The quantum confinement energies in one-dimensional quantum wires and zero-dimensional quantum dots are quite different. Using large-scale first-principles calculations, we systematically study the electronic structures of semiconductor (including group IV, III-V, and II-VI) surface-passivated quantum wires and dots. The band-gap energies of quantum wires and dots have the same scaling with … more

Date: March 30, 2004

Creator: Li, Jingbo & Wang, Lin-Wang

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Novel Metal-Sulfur-Based Air-Stable Passivation of GaAs with Very Low Surface State Densities

A new air-stable electronic surface passivation for GaAs and other III-V compound semiconductors that employs sulfur and a suitable metal ion, e.g., Zn, and that is robust towards plasma dielectric deposition has been developed. Initial improvements in photoluminescence are twice that of S-only treatments and have been preserved for >11 months with SiO{sub x}N{sub y} dielectric encapsulation. Photoluminescence and X-ray photoelectron spectroscopies indicate that the passivation consists of t… more

Date: August 9, 1999

Creator: Ashby, Carol I.H.; Baca, Albert G.; Chang, P.-C; Hafich, M.J.; Hammons, B.E. & Zavadil, Kevin R.

Item Type: Article

Partner: UNT Libraries Government Documents Department