scholarly journals Система локализованных экситонов на кислородных комплексах в CdS

2021 ◽  
Vol 55 (11) ◽  
pp. 1068
Author(s):  
Н.К. Морозова ◽  
И.Н. Мирошникова
Keyword(s):  
Stacking Faults ◽  
Growth Conditions ◽  
Optical Data ◽  
Excitation Density ◽  
Oxygen Solubility ◽  
High Excitation ◽  
Edge Emission ◽  
Exciton Region ◽  
Spectrum Band ◽  
Localized Excitons

Intense CdS luminescence in the blue and green spectral regions is widely used in all areas of optoelectronics. In this spectrum band are working on lasers CdS. This paper presents the results of a study of the exciton region of the CdS spectrum based on the theory of anti-intersecting bands (bands anticrossing theory - BAC) with the involvement of broader initial data for the analysis of optical properties. Depending on the growth conditions of CdS, the presence and change in the oxygen concentration, as well as the equilibrium of intrinsic point defects, which determines the change in the composition of the crystals. The concept of the nonuniform distribution of isoelectronic centers in the bulk of CdS due to their predominant segregation on compensating stacking faults is introduced. Cathodoluminescence (CL) spectra were studied using various recording methods, excitation intensity and temperature, as well as pulsed CL at high excitation intensities. In a scanning electron microscope from local registration and a high excitation density, the emission of the edge luminescence components of CdS was detected at 300 K To analyze the optical data, we used the capabilities of the method for constructing band models based on the BAC theory, which. collects extensive and multilateral information about specific samples. A model of a CdS O multizone with stacking faults is presented, which determines the spectrum of edge emission. An explanation of the nature of the green edge emission of cadmium sulfide as excitons localized on oxygen-containing complexes in SF layers has been obtained for the first time. It was found that the system of levels of localized excitons at stacking faults does not change either with temperature up to 300 K, or with a change in the oxygen solubility in the crystal to the limiting one. It is shown that the presence of isoelectronic oxygen centers appear itself in the electro-physical properties of crystals. Recommendations are given for the diagnostics of crystals suitable for the creation of luminescent systems or lasers that are stable in operation.

Crystalline perfection of chemical vapor deposited diamond films

1990 ◽  
Vol 5 (8) ◽  
pp. 1591-1594 ◽  
Author(s):  
A. V. Hetherington ◽  
C. J. H. Wort ◽  
P. Southworth
Keyword(s):  
Grain Boundaries ◽  
Microwave Plasma ◽  
Diamond Films ◽  
Stacking Faults ◽  
Chemical Vapor ◽  
Cvd Diamond ◽  
Growth Conditions ◽  
Crystalline Perfection ◽  
Planar Defects ◽  
Chemical Vapor Deposited

The crystalline perfection of microwave plasma assisted chemical vapor deposited (MPACVD) diamond films grown under various conditions has been examined by TEM. Most CVD diamond films thus far reported contain a high density of defects, predominantly twins and stacking faults on {111} planes. We show that under appropriate growth conditions, these planar defects are eliminated from the center of the crystallites, and occur only at grain boundaries where the growing crystallites meet.

scholarly journals Temperature dependence of ultrasharp luminescence lines in AlyIn1−yAs/AlxGa1−xAs self-assembled quantum dots

1996 ◽  
Vol 74 (S1) ◽  
pp. 216-219 ◽  
Author(s):  
S. Raymond ◽  
S. Fafard ◽  
S. Charbonneau
Keyword(s):  
Quantum Dots ◽  
Ground State ◽  
State Transition ◽  
Thermionic Emission ◽  
Excitation Density ◽  
High Excitation ◽  
Temperature Dependent ◽  
Time Resolved ◽  
Self Assembled ◽  
Intensity Evolution

Ensembles of~600 AlyIn1−yAs/AlxGa1−xAs self-assembled quantum dots (QDs) are investigated using photoluminescence (PL) and time-resolved PL in the visible. At very low excitation intensities, the PL spectrum shows multiple ultranarrow luminescence lines (FWHM ~200 μeV), which are attributed to the ground-state transition of a few dots (4 or less). The temperature and intensity evolution of these sharp lines is then monitored. The temperature-dependent measurements show that the line width and lifetime of the narrow lines remain constant up to the onset of thermionic, emission. Intensity-dependent measurements show that for high excitation density the collective background, emitted by the ensemble of QDs, is enhanced relative to the amplitude of individual ultranarrow lines.

Dynamics of laser-pumped Nd3+ laser media at high excitation density

1991 ◽  
Vol 48-49 ◽  
pp. 857-862 ◽  
Author(s):  
J.H. Schloss ◽  
L.L. Chase ◽  
L.K. Smith
Keyword(s):  
Excitation Density ◽  
High Excitation ◽  
Laser Media

On the Nanostructure of SiC

2010 ◽  
Vol 12 ◽  
pp. 99-104
Author(s):  
Maya Marinova ◽  
Efstathios K. Polychroniadis
Keyword(s):  
Silicon Carbide ◽  
Liquid Phase ◽  
Structural Properties ◽  
Liquid Phase Epitaxy ◽  
Stacking Faults ◽  
Growth Conditions ◽  
Small Energy ◽  
Long Period ◽  
Stacking Order

The present work deals with the structural properties of silicon carbide in nanoscale dimensions. The examined crystals were 6H-SiC grown by Liquid Phase Epitaxy. The study was concentrated on the stacking faults and any other differences from the “correct” stacking order of the Si-C bilayers for this polytype. Three main types of stacking faults were observed: (i) Cubic lamellae with thickness of four and two Si-C bilayers, always occurring in reverse stacking with respect to each other and separated by at least one unit cell of 6H-SiC; (ii) “twinned” 6H-SiC lamellae separated by a two-bilayer thick cubic inclusion. As a result the sequence in the “twinned” 6H-SiC changes from (3+3-) to (3-3+). (iii) Lamellae showing fringes, the interrelated distance of which suggests inclusion with sequence (22). Further, a high variety of sequences was found, leading to the appearance of rare long period polytypes or individual lamellae having their “own” stacking inside the 6H-SiC matrix. These nanostructured faults which deteriorate the quality of the grown material indicate also their “sensitivity” to any small or even infinitesimal change of the growth conditions, due to the very small energy among them.

The temperature dependence of the edge emission of GaSe single crystals at high excitation levels

1974 ◽  
Vol 11 (3) ◽  
pp. 274-276 ◽  
Author(s):  
R. Baltramiejūnas ◽  
G. Guseinov ◽  
V. Narkevičius ◽  
V. Niunka ◽  
J. Vaitkus ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Single Crystals ◽  
High Excitation ◽  
Edge Emission

Arsenic Incorporation in Gallium Nitride grown by Metalorganic Chemical Vapor Deposition using Dimethylhydrazine and Tertiarybutylarsenic

2000 ◽  
Vol 622 ◽  
Author(s):  
S. Kellermann ◽  
K. M. Yu ◽  
E. E. Haller ◽  
E. D. Bourret-Courchesne
Keyword(s):  
Vapor Deposition ◽  
Metalorganic Chemical Vapor Deposition ◽  
Doping Concentration ◽  
Stacking Faults ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Flow Ratio ◽  
As Doping ◽  
Mocvd Growth ◽  
Arsenic Incorporation

ABSTRACTMOCVD growth of As-doped GaN using dimethylhydrazine, triethylgallium and tertiarybutylarsenic has been investigated. A maximum doping concentration of 4.0 × 1019cm−3 at growth temperatures between 600°C and 800°C was obtained. At 1000°C the As doping level dropped below the SIMS detection limit of ∼1.0 × 1017cm−3. The As incorporation depended only weakly on variations of the V/III molar flow ratio between 11 and 61. Raising the As/V molar flow ratio from 0.01 to 0.06 increased the As concentration which then decreased by further increase to 0.11. Different morphologies of the layers were found depending on the growth conditions. A surfactant-like behavior of As was observed leading to smooth GaN films grown on top of the As-doped GaN layer. Two characteristic luminescence peaks at 3.31 eV and 3.425 eV were found for samples doped with As below 900°C. These spectral features are believed to originate at extended lateral defects - presumably stacking faults.

scholarly journals X-ray investigation of polytype distribution in InAs nanowires during MBE growth

2014 ◽  
Vol 70 (a1) ◽  
pp. C748-C748
Author(s):  
Ullrich Pietsch ◽  
Andreas Biermanns ◽  
Emmanouil Dimakis ◽  
Lutz Geelhaar ◽  
Anton Davydok ◽  
...  
Keyword(s):  
Time Evolution ◽  
Stacking Faults ◽  
Growth Conditions ◽  
Growth Mode ◽  
Ex Situ ◽  
Growth Time ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates ◽  
Liquid Indium

The monolithic integration of III-V semiconductors with Si is the ideal way to combine the superior optoelectronic properties of the compound semiconductors with the mature Si technology. This integration can be realized by growing epitaxially dislocation-free III-V NWs on Si substrates either in the vapor-liquid-solid (VLS) or in the vapor-solid (VS) mode associated with the presence or absence, respectively, of group-III liquid droplets on the NW tips [1]. In this work, we investigate the correlation between the growth mode and the forming polytypes in InAs NWs grown on Si(111). The growth was performed in the molecular beam epitaxy chamber of beamline 11XU at Spring8 [2], while the structural dynamics was probed by in situ x-ray diffraction. Specifically, the time evolution of the formation of wurtzite (WZ) and zincblende (ZB) polytypes was monitored during the NW growth. Despite the As-rich growth conditions, a spontaneous build-up of liquid In on Si was found to be present in the nucleation phase, where the InAs nuclei mainly grow in the WZ phase with low number of stacking faults. Shortly after the nucleation, the liquid In is consumed by the excessive As, and the growth continues in the VS mode with an increasing density of stacking faults forming in the NW crystal. The time evolution of the liquid Indium signal (Fig. (a)) correlates well with the time evolution of wurzite growth rate (Fig (b)). The latter saturates at a time where the liquid indium disappers, i.e. where the VLS changes into the VS mode, whereas the zinc-blende polytypes grow almost continuous in both VLS and VS growth mode. The dynamics of stacking faults density was determined quantitatively by ex-situ X-ray diffraction measuring thestacking fault induced increase of the peak width of wurtzite reflections at InAs nanowire samples of different length ; i.e. growth time [3].

Sign in / Sign up

Export Citation Format

Share Document