Evidence for polarons and itinerant carriers in superconductivity from time-resolved optical measurements on YBa2Cu3O7-△

1997 ◽  
Vol 10 (4) ◽  
pp. 337-341 ◽  
Author(s):  
D. Mihailovic ◽  
C. Stevens ◽  
J. Demsar ◽  
B. Podobnik ◽  
D. C. Smith ◽  
...  
Keyword(s):  
Optical Measurements ◽  
Time Resolved

scholarly journals Instrument response function acquisition in reflectance geometry for time-resolved diffuse optical measurements

2019 ◽  
Vol 11 (1) ◽  
pp. 240 ◽  
Author(s):  
Ileana Pirovano ◽  
Rebecca Re ◽  
Alessia Candeo ◽  
Davide Contini ◽  
Alessandro Torricelli ◽  
...  
Keyword(s):  
Response Function ◽  
Optical Measurements ◽  
Time Resolved ◽  
Instrument Response Function ◽  
Instrument Response

Solidification of highly undercooled liquid silicon produced by pulsed laser melting of ion-implanted amorphous silicon: Time-resolved and microstructural studies

1987 ◽  
Vol 2 (5) ◽  
pp. 648-680 ◽  
Author(s):  
D. H. Lowndes ◽  
S. J. Pennycook ◽  
G. E. Jellison ◽  
S. P. Withrow ◽  
D. N. Mashburn
Keyword(s):  
Pulsed Laser ◽  
Optical Measurements ◽  
Undercooled Liquid ◽  
Laser Melting ◽  
Time Resolved ◽  
Fine Grained ◽  
Explosive Crystallization ◽  
Epitaxial Regrowth ◽  
Surface Melt ◽  
Melt Duration

Nanosecond resolution time-resolved visible (632.8 nm) and infrared (1152 nm) reflectivity measurements, together with structural and Z-contrast transmission electron microscope (TEM) imaging, have been used to study pulsed laser melting and subsequent solidification of thick (190–410 nm) amorphous (a) Si layers produced by ion implantation. Melting was initiated using a KrF (248 nm) excimer laser of relatively long [45 ns full width half maximum (FWHM)] pulse duration; the microstructural and time-resolved measurements cover the entire energy density (E1) range from the onset of melting (at ∼ 0.12J/cm2) up to the onset of epitaxial regrowth (at ∼ 1.1 J/cm2). At low E1 the infrared reflectivity measurements were used to determine the time of formation, the velocity, and the final depth of “explosively” propagating buried liquid layers in 410 nm thick a-Si specimens that had been uniformly implanted with Si, Ge, or Cu over their upper ∼ 300 nm. Measured velocities lie in the 8–14 m/s range, with generally higher velocities obtained for the Ge- and Cu-implanted “a-Si alloys.” The velocity measurements result in an upper limit of 17 (± 3) K on the undercooling versus velocity relationship for an undercooled solidfying liquid-crystalline Si interface. The Z-contrast scanning TEM measurements of the final buried layer depth were in excellent agreement with the optical measurements. The TEM study also shows that the “fine-grained polycrystalline Si” region produced by explosive crystallization of a-Si actually contains large numbers of disk-shaped Si flakes that can be seen only in plan view. These Si flakes have highly amorphous centers and laterally increasing crystallinity; they apparently grow primarily in the lateral direction. Flakes having this structure were found both at the surface, at low laser E1, and also deep beneath the surface, throughout the “fine-grained poly-Si” region formed by explosive crystallization, at higher E1. Our conclusion that this region is partially amorphous (the centers of flakes) differs from earlier results. The combined structural and optical measurements suggest that Si flakes nucleate at the undercooled liquid-amorphous interface and are the crystallization events that initiate explosive crystallization. Time-resolved reflectivity measurements reveal that the surface melt duration of the 410 nm thick a-Si specimens increases rapidly for 0.3E1 <0.6 J/cm2, but then remains nearly constant for E1 up to ∼ 1.0 J/cm2. For 0.3 < E1 < 0.6 J/cm2 the reflectivity exhibits a slowly decaying behavior as the near-surface pool of liquid Si fills up with growing large grains of Si. For higher E1, a flat-topped reflectivity signal is obtained and the microstructural and optical studies together show that the principal process occurring is increasingly deep melting followed by more uniform regrowth of large grains back to the surface. However, cross-section TEM shows that a thin layer of fine-grained poly-Si still is formed deep beneath the surface for E1<0.9 J/cm2, implying that explosive crystallization occurs (probably early in the laser pulse) even at these high E1 values. The onset of epitaxial regrowth at E1 = 1.1 J/cm2 is marked by a slight decrease in surface melt duration.

Time-resolved optical measurements of minority carrier recombination in a mid-wave infrared InAsSb alloy and InAs/InAsSb superlattice

2012 ◽  
Vol 101 (9) ◽  
pp. 092109 ◽  
Author(s):  
B. V. Olson ◽  
E. A. Shaner ◽  
J. K. Kim ◽  
J. F. Klem ◽  
S. D. Hawkins ◽  
...  
Keyword(s):  
Minority Carrier ◽  
Optical Measurements ◽  
Time Resolved ◽  
Carrier Recombination

Characterization of Minority-Carrier Hole Transport in Nitride-Based Light-Emitting Diodes with Optical and Electrical Time-Resolved Techniques

2004 ◽  
Vol 831 ◽  
Author(s):  
R. J. Kaplar ◽  
S. R. Kurtz ◽  
D. D. Koleske ◽  
A. A. Allerman ◽  
A. J. Fischer ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Minority Carrier ◽  
Hole Transport ◽  
Optical Measurements ◽  
Hole Density ◽  
Transport Parameters ◽  
Two Phase ◽  
Time Resolved ◽  
Light Emitting ◽  
Order Of Magnitude

ABSTRACTForward-to-reverse bias step-recovery measurements were performed on In.07Ga.93N/GaN and Al.36Ga.64N/Al.46Ga.54N quantum-well (QW) light-emitting diodes grown on sapphire. With the QW sampling the minority-carrier hole density at a single position, distinctive two-phase optical decay curves were observed. Using diffusion equation solutions to self-consistently model both the electrical and optical responses, hole transport parameters τp = 758 ± 44 ns, Lp = 588 ± 45 nm, and μp = 0.18 ± 0.02 cm2/Vs were obtained for GaN. The mobility was thermally activated with an activation energy of 52 meV, suggesting trap-modulated transport. Optical measurements of sub-bandgap peaks exhibited slow responses approaching the bulk lifetime. For Al.46Ga.54N, a longer lifetime of τp = 3.0 μs was observed, and the diffusion length was shorter, Lp ≈ 280 nm. Mobility was an order of magnitude smaller than in GaN, μp ≈ 10−2 cm2/Vs, and was insensitive to temperature, suggesting hole transport through a network of defects.

scholarly journals Carbon Nanotube Photophysics

MRS Bulletin ◽  
2004 ◽  
Vol 29 (4) ◽  
pp. 276-280 ◽  
Author(s):  
A. Jorio ◽  
R. Saito ◽  
T. Hertel ◽  
R.B. Weisman ◽  
G. Dresselhaus ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Charge Carrier ◽  
Carrier Dynamics ◽  
Optical Measurements ◽  
Future Research ◽  
Time Resolved ◽  
Van Hove Singularities ◽  
Charge Carrier Dynamics ◽  
Potential Applications ◽  
Photoluminescence Studies

AbstractIn single-walled carbon nanotubes (SWNTs), their electronic and vibrational structure as well as their charge-carrier dynamics are crucial for potential ultrasmall optical device applications. SWNT properties have now been obtained from optical absorption and time-resolved photoemission and, at the single-nanotube level, by resonance Raman scattering and photoluminescence studies. This article presents an overview of SWNT photophysics, discussing important findings for the characterization of carbon nanotube properties and directions for future research and potential applications. The unique optical properties observed in SWNTs are due to the one-dimensional confinement of electronic states, resulting in van Hove singularities in the nanotube density of states. Optical measurements of phonons, charge-carrier dynamics, and the electronic transition energy van Hove singularities are discussed.

Time-Resolved and Post-Irradiation Studies of the Interaction of High-Power Pulsed Microwave Radiation with Silicon

1986 ◽  
Vol 74 ◽  
Author(s):  
R. B. James ◽  
P. R. Bolton ◽  
R. A. Alvarez ◽  
R. E. Valiga ◽  
W. H. Christie
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Surface Region ◽  
Surface Damage ◽  
Threshold Value ◽  
Optical Measurements ◽  
Time Resolved ◽  
Near Surface ◽  
Reflected Power ◽  
Secondary Ion

AbstractWe have measured the microwave-induced damage to the near-surface region of silicon for 1.9-μs pulses at a frequency of 2.856 GHz and a pulse power of up to 7.2 MW. Rectangular samples were irradiated in a test section of WR-284 waveguide that was filled with freon to a pressure of 30 psig. Incident, transmitted and reflected powers were monitored with directional couplers and fast diodes. The results of the time-resolved optical measurements show that the onset of surface damage is accompanied by a large increase in the reflected power. Examination of the irradiated surfaces shows that the degree of damage is greatest near the edges of the samples. Using secondary ion mass spectrometry to profile the implanted As, we find that the microwave pulses can melt the near-surface region of the material for pulse powers exceeding a threshold value.

Textured crystallization of germanium telluride

1992 ◽  
Vol 50 (1) ◽  
pp. 24-25
Author(s):  
M. Libera
Keyword(s):  
Laser Annealing ◽  
Optical Storage ◽  
Film Plane ◽  
Optical Measurements ◽  
Transformation Kinetics ◽  
Time Resolved ◽  
Germanium Telluride ◽  
Crystal Matrix ◽  
States Data ◽  
Amorphous States

Phase-change optical storage uses a focused laser to locally switch a chalcogenide film between the crystalline and amorphous states. Data bits are stored as amorphous spots in a crystal matrix. They can be erased by laser annealing, but applications require fast crystallization during the erase. The crystallization kinetics are not well understood. A recent study of germanium telluride (GeTe) used time-resolved optical measurements and TEM to show that crystallization in Ge48Te52 films is dominated by the 2-D growth of crystallites in the film plane. Current work relates the complex crystallite morphology to the operative transformation kinetics.

Sagnac interferometer for time-resolved magneto-optical measurements

2022 ◽  
Vol 93 (1) ◽  
pp. 013903
Author(s):  
Hyeokjun Heo ◽  
Taeho Kim ◽  
Yungi Jeong ◽  
Hangyeol Park ◽  
Joonho Jang
Keyword(s):  
Optical Measurements ◽  
Sagnac Interferometer ◽  
Time Resolved
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