scholarly journals Diamagnetic shift of the A free exciton in CuGaSe2 single crystals

2010 ◽  
Vol 97 (16) ◽  
pp. 162101 ◽  
Author(s):  
F. Luckert ◽  
M. V. Yakushev ◽  
C. Faugeras ◽  
A. V. Karotki ◽  
A. V. Mudryi ◽  
...  
Keyword(s):  
Single Crystals ◽  
Free Exciton ◽  
Diamagnetic Shift

Anthracene fluorescence at low temperatures. I. Purified single crystals

1972 ◽  
Vol 25 (7) ◽  
pp. 1411 ◽  
Author(s):  
LE Lyons ◽  
LJ Warren
Keyword(s):  
Low Temperature ◽  
Single Crystals ◽  
Fluorescence Spectrum ◽  
Low Temperatures ◽  
Free Exciton ◽  
Deformation Bands ◽  
Exciton Emission ◽  
Polarized Emission ◽  
Impurity Bands ◽  
Phonon Structure

The low-temperature fluorescence spectrum of purified vapour-grown anthracene single crystals is presented and the free-exciton emission distinguished from a number of defect or impurity bands present even in the purest crystals. In assigning the observed bands the symmetry of the active vibrations and the origin of background fluorescence and deformation bands are discussed. The phonon structure in the region of the fluorescence origin was found to be almost completely b-polarized. Emission of electronic origin (25103 cm-1) was too weak to be observed. Polarization ratios of the principal vibronio bands at 5.6 K are given.

The Effects Of Substitutional Alkaline Metals In Zinc Vacancy Of Zincselenide Single Crystals Grown By The Sublimation Method

1996 ◽  
Vol 442 ◽  
Author(s):  
Kenji Yoshino ◽  
Kouji Maeda ◽  
Atsuhiko Fukuyama ◽  
Yoshito Akashi ◽  
Kiyohisa Imada ◽  
...  
Keyword(s):  
Single Crystals ◽  
Free Exciton ◽  
Energy Shift ◽  
Acceptor Pair ◽  
Deep Acceptor ◽  
Impurity Atoms ◽  
Peak Energy ◽  
Sublimation Method ◽  
Donor Acceptor ◽  
Metal Doped

AbstractThe photoluminescence measurements of alkaline metal doped zincselenide (ZnSe) single crystals were carried out to investigate how the impurity atoms substitute the intrinsic vacancy. Sample are grown by the sublimation method and the Li and Na with the concentrations of 0.1, 0.25 and 0.5 mol% were incorporated simultaneously. In the PL spectra with lower impurity concentrations, bound exciton lines of deep acceptor and donor-acceptor pair (DAP) bands were clearly observed accompanied by a weak free exciton line. Although the bound exciton lines becomes smaller with increasing the impurity concentration, the DAP band remains strong and its peak energy shift to lower energy side with the concentration. The decrease of the bound exciton lines is drastic for Li-doped sample than Na-doped sample. This indicates that Li atoms more easily occupy the Zn vacancies than Na.

Photoluminescence Of Zincselenide Single Crystals Annealed In Zinc Or Selenium Atmosphere

1994 ◽  
Vol 348 ◽  
Author(s):  
Kenji Yoshino ◽  
Yasushi Matsushima ◽  
Hiroyoshi Kinoshita ◽  
Makoto Hiramatsu
Keyword(s):  
Single Crystals ◽  
Grown Crystal ◽  
Free Exciton ◽  
Bandgap Energy ◽  
Reflection Spectroscopy ◽  
Exciton Line ◽  
Annealing Effects ◽  
Sublimation Method ◽  
Pl Spectrum

ABSTRACTZincselenide single crystals grown by the sublimation method are annealed in Zn or Se atmosphere. The annealing effects are examined by means of photoluminescence (PL) and reflection spectroscopy at 4.2 K. In the PL spectrum for the as-grown crystal, bound exciton lines (I2, I1) are observed. For the Zn-annealed crystal, the free exciton line is clearly observed. For the Se-annealed crystal, peak positions of all lines shift to the higher energies and all lines become sharp, compared with the spectra for the as-grown crystal. It is concluded that Sc-vacancies affect the bandgap energy more than Zn-vacancies do.

scholarly journals Excitons in PL spectra of Cu(In, Ga)Se-=SUB=-2-=/SUB=- single crystal -=SUP=-*-=/SUP=-

2019 ◽  
Vol 61 (5) ◽  
pp. 1002
Author(s):  
E. Skidchenko ◽  
M.V. Yakushev ◽  
L. Spasevski ◽  
P.R. Edwards ◽  
M.A. Sulimov ◽  
...  
Keyword(s):  
Single Crystals ◽  
Free Exciton ◽  
Excitation Intensity ◽  
Structural Quality ◽  
Near Band Edge ◽  
Bridgman Technique ◽  
Pl Spectra ◽  
Vertical Bridgman ◽  
Ga Content

AbstractA photoluminescence (PL) study of Cu(In,Ga)Se_2 (CIGSe) single crystals, (grown by the vertical Bridgman technique) with the [Ga]/[Ga + In] ratio of 7 and 12% and the [Cu]/[In + Ga] ratio greater than unity, as measured by energy dispersive spectroscopy, is presented. Analysis of the excitation intensity and temperature dependence of the PL spectra suggested the excitonic nature of the observed near-band-edge emissions peaks. Free and bound excitons in CIGSe single crystals with both 7 and 12% Ga content are clearly observed, analyzed and identified. An activation energy of 19 meV is determined for the free exciton in the PL spectra of the sample with 12% Ga. The presence of the excitons demonstrated a high structural quality of the material.

Low-temperature luminescence in organic-inorganic lead iodide perovskite single crystals

2021 ◽  
Author(s):  
Irina Vladimirovna Zhevstovskikh ◽  
Nikita Averkiev ◽  
Maksim Sarychev ◽  
Olga Semenova ◽  
Oleg Tereshchenko
Keyword(s):  
Single Crystals ◽  
Thermal Evolution ◽  
Free Exciton ◽  
Orthorhombic Phase ◽  
Lead Iodide ◽  
Acceptor Pair ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Pl Emission ◽  
Methylammonium Lead Iodide

Abstract We present temperature and laser-power dependent photoluminescence (PL) study of methylammonium lead iodide (CH3NH3PbI3) single crystals in the orthorhombic phase. At temperatures below 140 K, we revealed the multi-component PL emission. In addition to a free exciton with an energy of 1.65 eV, we found emission bands with peaks approximately equal to 1.6 eV, 1.52 eV, and 1.48 eV. Analysis of the thermal evolution of the intensities, peak positions, and linewidths of all the PL bands allowed one to determine their origin. We attributed the PL peak with the energy of 1.6 eV to a bound exciton, while the free exciton-bound exciton splitting energy is 50-60 meV. The PL emission with an energy of 1.52 eV can be explained by the donor-acceptor pair (DAP) recombination, where donor and acceptor defects have a depth of about 12 meV and 120 meV, respectively. MA (CH3NH3) interstitials (MA+i ) and lead vacancies (V2-Pb) are the most suitable for the DAP transition to occur in CH3NH3PbI3 crystals. The 1.48 eV PL emission is consistent with the recombination of self-trapped excitons, and interstitial iodine is likely to be an active trap source. We found the variation of the self-trapped depth from 15 meV (at T<80 K) to 53 meV (at T>80 K) with increasing the temperature. Although the multi-component PL emission in CH3NH3PbI3 single crystals appears at low temperatures, defects and excitonic traps that cause this emission can affect the photophysics of hybrid perovskites at higher temperatures.

scholarly journals Photoluminescence study on GaN homoepitaxial layers grown by molecular beam epitaxy

1996 ◽  
Vol 1 ◽  
Author(s):  
H. Teisseyre ◽  
G. Nowak ◽  
M. Leszczynski ◽  
I. Grzegory ◽  
M. Bockowski ◽  
...  
Keyword(s):  
High Resolution ◽  
Molecular Beam Epitaxy ◽  
Energy Range ◽  
Single Crystals ◽  
Molecular Beam ◽  
Free Exciton ◽  
X Ray Diffraction ◽  
Photoluminescence Study ◽  
X Ray ◽  
Homoepitaxial Layers

GaN epitaxial layers on GaN single crystals were grown using molecular beam epitaxy with an NH3 source. The deposited layers were examined by high resolution x-ray diffraction and photoluminescence (PL) spectroscopy. We observed strong and extremely narrow (half-widths of 0.5 meV) lines related to the bound excitons. In the higher energy range we observed three strong lines. Two of them are commonly attributed to free exciton transitions A (3.4785 eV) and B (3.483 eV). Their energetic positions are characteristic of strain-free GaN material.

The Microstructure of Shock-Synthesized Diamond

1967 ◽  
Vol 25 ◽  
pp. 324-325
Author(s):  
Lucien F. Trueb
Keyword(s):  
Single Crystals ◽  
Preferred Orientation ◽  
High Magnification ◽  
Texture Pattern ◽  
Shock Process ◽  
New Type ◽  
Diffraction Diagram

A new type of synthetic industrial diamond formed by an explosive shock process has been recently developed by the Du Pont Company. This material consists of a mixture of two basically different forms, as shown in Figure 1: relatively flat and compact aggregates of acicular crystallites, and single crystals in the form of irregular polyhedra with straight edges.Figure 2 is a high magnification micrograph typical for the fibrous aggregates; it shows that they are composed of bundles of crystallites 0.05-0.3 μ long and 0.02 μ. wide. The selected area diffraction diagram (insert in Figure 2) consists of a weak polycrystalline ring pattern and a strong texture pattern with arc reflections. The latter results from crystals having preferred orientation, which shows that in a given particle most fibrils have a similar orientation.

A New Defect in Polyethylene Single Crystals

1973 ◽  
Vol 31 ◽  
pp. 70-71
Author(s):  
E. L. Thomas ◽  
S. L. Sass
Keyword(s):  
Single Crystals ◽  
Screw Dislocation ◽  
Small Distance ◽  
Dipole Model ◽  
Dislocation Dipole ◽  
Chain Folding ◽  
Black And White ◽  
Polymer Crystal ◽  
Different Types

In polyethylene single crystals pairs of black and white lines spaced 700-3,000Å apart, parallel to the [100] and [010] directions, have been identified as microsector boundaries. A microsector is formed when the plane of chain folding changes over a small distance within a polymer crystal. In order for the different types of folds to accommodate at the boundary between the 2 fold domains, a staggering along the chain direction and a rotation of the chains in the plane of the boundary occurs. The black-white contrast from a microsector boundary can be explained in terms of these chain rotations. We demonstrate that microsectors can terminate within the crystal and interpret the observed terminal strain contrast in terms of a screw dislocation dipole model.

Preferential Sputtering of Ni3Al Single Crystals Studied Using Atom-Probe Field-Ion Microscopy and XPS

1981 ◽  
Vol 39 ◽  
pp. 16-17
Author(s):  
M.P. Thomas ◽  
A.R. Waugh ◽  
M.J. Southon ◽  
Brian Ralph
Keyword(s):  
Single Crystals ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
Depth Profiling ◽  
Analytical Techniques ◽  
Atom Probe ◽  
Probe Field ◽  
Preferential Sputtering ◽  
Argon Ion Bombardment ◽  
Argon Ion

It is well known that ion-induced sputtering from numerous multicomponent targets results in marked changes in surface composition (1). Preferential removal of one component results in surface enrichment in the less easily removed species. In this investigation, a time-of-flight atom-probe field-ion microscope A.P. together with X-ray photoelectron spectroscopy XPS have been used to monitor alterations in surface composition of Ni3Al single crystals under argon ion bombardment. The A.P. has been chosen for this investigation because of its ability using field evaporation to depth profile through a sputtered surface without the need for further ion sputtering. Incident ion energy and ion dose have been selected to reflect conditions widely used in surface analytical techniques for cleaning and depth-profiling of samples, typically 3keV and 1018 - 1020 ion m-2.

Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

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