scholarly journals Femtosecond Time-Resolved Electron Diffraction: Applications for Laser Melting and Ablation

2015 ◽  
Vol 43 (3) ◽  
pp. 149
Author(s):  
Masaki HADA
Keyword(s):  
Electron Diffraction ◽  
Laser Melting ◽  
Time Resolved

Electron Channeling Patterns

1977 ◽  
Vol 35 ◽  
pp. 12-13
Author(s):  
David C. Joy
Keyword(s):  
Electron Diffraction ◽  
Incidence Angle ◽  
Photographic Plate ◽  
Diffraction Effect ◽  
Angle Of Incidence ◽  
Bulk Single Crystal ◽  
Time Resolved ◽  
Electron Channeling ◽  
Spatially Resolved ◽  
Large Bulk

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).

scholarly journals Femtosecond time-resolved MeV electron diffraction

2015 ◽  
Vol 17 (6) ◽  
pp. 063004 ◽  
Author(s):  
Pengfei Zhu ◽  
Y Zhu ◽  
Y Hidaka ◽  
L Wu ◽  
J Cao ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Time Resolved

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.

Performance of an Indium-sealed S-band RF Photoelectron Gun for Time-resolved Electron Diffraction Experiments

2019 ◽  
Vol 74 (1) ◽  
pp. 24-29 ◽  
Author(s):  
Hyun Woo Kim ◽  
Kyu-Ha Jang ◽  
In Hyung Baek ◽  
Kitae Lee ◽  
Young Uk Jeong ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Time Resolved ◽  
Photoelectron Gun

scholarly journals Towards understanding triiodide photochemistry in the solid state by femtosecond electron diffraction

2019 ◽  
Vol 205 ◽  
pp. 09007
Author(s):  
Rui Xian ◽  
Stuart A. Hayes ◽  
Gaston Corthey ◽  
Carole A. Morrison ◽  
Alexander Marx ◽  
...  
Keyword(s):  
Solid State ◽  
Electron Diffraction ◽  
Large Amplitude ◽  
Atomic Level ◽  
Coherent Motion ◽  
Reaction Products ◽  
Time Resolved ◽  
Femtosecond Electron Diffraction

The photochemistry of the triiodide anion has been investigated by femtosecond electron diffraction. The time-resolved signal indicates the presence of reaction products and large-amplitude coherent motion produced by participating species. To reconstruct the atomic detail of the reaction and identify the major contributors to the detected signal, we outline the approach for atomic-level reconstruction.

Phonon confinement effects in ultrathin epitaxial bismuth films on silicon studied by time-resolved electron diffraction

2009 ◽  
Vol 80 (2) ◽  
Author(s):  
B. Krenzer ◽  
A. Hanisch-Blicharski ◽  
P. Schneider ◽  
Th. Payer ◽  
S. Möllenbeck ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Phonon Confinement ◽  
Confinement Effects ◽  
Time Resolved ◽  
Bismuth Films

Congruent Melting Temperatures of Si-As Alloys Measured During Pulsed-Laser Melting and Rapid Solidification

1992 ◽  
Vol 279 ◽  
Author(s):  
J. A. Kittl ◽  
R. Reitano ◽  
M. J. Aziz ◽  
D. P. Brunco ◽  
M. O. Thompson
Keyword(s):  
Partition Coefficient ◽  
Temperature Measurement ◽  
Rutherford Backscattering Spectrometry ◽  
Pulsed Laser ◽  
Heat Of Fusion ◽  
Interface Temperature ◽  
Congruent Melting ◽  
Laser Melting ◽  
Time Resolved ◽  
Melting Temperatures

ABSTRACTThe solidification of Si-As alloys induced by pulsed laser melting was studied at regrowth velocities where the partition coefficient is close to unity. The congruent melting temperatures, TO, of Si-As alloys were determined using a temperature measurement technique developed for this work, and were confirmed with TOmeasurements using three other methods. The time-resolved temperature measurement uses a thin-film platinum thermistor, below and electrically isolated from the Si-As alloy layer, to directly measure the temperature during solidification. This, combined with measurements of transient conductance of the Si-As alloy, time-resolved reflectivity and Rutherford Backscattering Spectrometry, permitted the determination of the solid-liquid interface temperature, velocity and partition coefficient, the latent heat of fusion and TO for Si - 4.5 at. % As and Si - 9 at. % As alloys.

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