Room Temperature Excitonic Absorption in Small Cds Crystallites

1989 ◽  
Vol 164 ◽  
Author(s):  
D.K. Rai ◽  
Binod Kumar
Keyword(s):  
Crystallite Size ◽  
Room Temperature ◽  
Laser Intensity ◽  
Optical Nonlinearities ◽  
Transmitted Intensity ◽  
Crystallite Growth ◽  
Exciton Absorption ◽  
Excitonic Absorption ◽  
Absorption Features ◽  
Cds Crystallites

AbstractThe absorption characteristics of commercial CdS-containing yellow glass which shows constant transmitted intensity over a range of incident CW laser intensity have been studied at room temperature. Although the thick specimen (t>0.6 mm) shows only a broad step-like feature near λ>460 nm, a thin (t-0.09 mm) specimen shows two absorption features which can be interpreted as the first two quantum-confined exciton absorption features corresponding to a crystallite size of -45 Å. The absorption spectrum of a sample (t∼O.6 mm) heated for 15 min. at 700°C shows two new absorption features at 450 nm and 380 nm, which correspond to a much smaller crystallite size of -25 Å. This reduction in size is not inconsistent with estimates made from a well-known model for crystallite growth. Some consequences of these changes in the absorption features on the optical nonlinearities of the glass will be discussed.

Room‐temperature excitonic optical nonlinearities of molecular beam epitaxially grown ZnSe thin films

1988 ◽  
Vol 52 (3) ◽  
pp. 182-184 ◽  
Author(s):  
N. Peyghambarian ◽  
S. H. Park ◽  
S. W. Koch ◽  
A. Jeffery ◽  
J. E. Potts ◽  
...  
Keyword(s):  
Thin Films ◽  
Room Temperature ◽  
Molecular Beam ◽  
Optical Nonlinearities ◽  
Znse Thin Films

Room-temperature optical nonlinearities of electronic origin in ZnSe

1990 ◽  
Vol 7 (5) ◽  
pp. 868 ◽  
Author(s):  
W. Ji ◽  
J. R. Milward ◽  
A. K. Kar ◽  
B. S. Wherrett ◽  
C. R. Pidgeon
Keyword(s):  
Room Temperature ◽  
Optical Nonlinearities

X-Ray Diffraction Analysis on Crystallite Development of Nanostructured Aluminium

2006 ◽  
Vol 118 ◽  
pp. 53-58
Author(s):  
Elisabeth Meijer ◽  
Nicholas Armstrong ◽  
Wing Yiu Yeung
Keyword(s):  
Crystallite Size ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Equal Channel Angular Extrusion ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Integral Breadth ◽  
X Ray ◽  
Heat Treated ◽  
Diffraction Peaks

This study is to investigate the crystallite development in nanostructured aluminium using x-ray line broadening analysis. Nanostructured aluminium was produced by equal channel angular extrusion at room temperature to a total deformation strain of ~17. Samples of the extruded metal were then heat treated at temperatures up to 300oC. High order diffraction peaks were obtained using Mo radiation and the integral breadth was determined. It was found that as the annealing temperature increased, the integral breadth of the peak reflections decreased. By establishing the modified Williamson-Hall plots (integral breadth vs contract factor) after instrumental correction, it was determined that the crystallite size of the metal was maintained ~80 nm at 100oC. As the annealing temperature increased to 200oC, the crystallite size increased to ~118 nm. With increasing annealing temperature, the hardness of the metal decreased from ~60 HV to ~45 HV.

Molecular Beam Epitaxy of Znl-x Cdx Se/ZnSe Heterostructures And Their Optical Properties

1991 ◽  
Vol 228 ◽  
Author(s):  
H. Luo ◽  
N. Samarth ◽  
J. K. Furdyna ◽  
H. Jeon ◽  
J. Ding ◽  
...  
Keyword(s):  
Optical Properties ◽  
Molecular Beam Epitaxy ◽  
Quantum Wells ◽  
Room Temperature ◽  
Molecular Beam ◽  
Stimulated Emission ◽  
Optically Pumped ◽  
Absorption Coefficients ◽  
Excitonic Absorption ◽  
Lasing Mechanism

ABSTRACTSuperlattices and quantum wells of Znl-xCdxSe/ZnSe, and heterostructures based on ZnSe/CdSe digital alloys have been grown by molecular beam epitaxy (MBE). Their optical properties were studied with particular emphasis on excitonic absorption and photopumped stimulated emission. Excitonic absorption is easily observable up to 400 K, and is characterized by extremely large absorption coefficients (α = 2×105cm−1). Optically pumped lasing action is obtained at room temperature with a typical threshold intensity of 100 kW/cm2. The lasing mechanism in these II-VI quantum wells appears to be quite different from that in the better studied III-V materials: in our case, the onset of stimulated emission occurs before the saturation of the excitonic absorption, and the stimulated emission occurs at an energy lower than that of the excitonic absorption.

scholarly journals Influence of sintering temperature and pressure on crystallite size and lattice defect structure in nanocrystalline SiC

2007 ◽  
Vol 22 (5) ◽  
pp. 1314-1321 ◽  
Author(s):  
J. Gubicza ◽  
S. Nauyoks ◽  
L. Balogh ◽  
J. Labar ◽  
T.W. Zerda ◽  
...  
Keyword(s):  
Crystallite Size ◽  
Defect Structure ◽  
Sintering Temperature ◽  
Profile Analysis ◽  
Lattice Defect ◽  
Line Profile Analysis ◽  
Crystallite Growth ◽  
X Ray ◽  
Transmission Electron ◽  
Temperature And Pressure

Microstructure of sintered nanocrystalline SiC is studied by x-ray line profile analysis and transmission electron microscopy. The lattice defect structure and the crystallite size are determined as a function of pressure between 2 and 5.5 GPa for different sintering temperatures in the range from 1400 to 1800 °C. At a constant sintering temperature, the increase of pressure promotes crystallite growth. At 1800 °C when the pressure reaches 8 GPa, the increase of the crystallite size is impeded. The grain growth during sintering is accompanied by a decrease in the population of planar faults and an increase in the density of dislocations. A critical crystallite size above which dislocations are more abundant than planar defects is suggested.

Optical nonlinearities at transient quenching of EL2 defect at room temperature

1999 ◽  
Vol 170 (1-3) ◽  
pp. 149-160 ◽  
Author(s):  
M. Sūdžius ◽  
A. Bastys ◽  
K. Jarašiūnas
Keyword(s):  
Room Temperature ◽  
Optical Nonlinearities

Thermal Annealing Behavior of Si-DLC Ibad Coatings

1996 ◽  
Vol 438 ◽  
Author(s):  
C. G. Fountzoulas ◽  
J. D. Demaree ◽  
L. C. Sengupta ◽  
J. K. Hirvonen
Keyword(s):  
Room Temperature ◽  
Ion Beam ◽  
Silicon Substrates ◽  
Carbon Coatings ◽  
Dlc Coatings ◽  
Annealing Behavior ◽  
Ion Beam Assisted Deposition ◽  
Disk Friction ◽  
Knoop Microhardness ◽  
Absorption Features

AbstractAmorphous, 700 nm thick, diamond-like carbon coatings containing silicon (Si-DLC), farmed by Ar+ ion beam assisted deposition (IBAD) on silicon substrates, were annealed in air at temperatures ranging from room temperature to 600°C for 30 minutes. RBS analysis showed that the composition of the films remained the same up to 200°C, but at higher temperatures the Si-DLC coatings began to oxidize at the outer surface of the coating, forming a surface layer of SiO2. After in-air annealing at 600°C the coating had been completely converted to SiO2, with no trace of carbon seen by RBS. FTIR spectra of the unannealed coatings showed a very broad mode typical of Si-DLC bonding as well as some absorption features associated with Si and SiO2. Above 200°C the transmission mode shifted to higher frequencies which may be caused by the growth of SiO2 and the decrease of the Si-DLC film thickness. The room temperature ball-on-disk friction coefficient of the coating against a 1/2′′ diameter 440 C steel ball at 1 N load ranged from 0.2 for the original coating up to 0.5 after a 100° anneal and returned to 0.2 after annealing at 200–400°C and fell to 0.12 after a 500°C exposure. The average Knoop microhardness (uncorrected for substrate effects) was 10 GPa (1,000 KHN) for coatings annealed at temperatures as high as 400°C. All coatings up to 500 °C passed the qualitative “Scotch Tape” test.

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