scholarly journals Heterogeneous to homogeneous melting transition visualized with ultrafast electron diffraction

Science ◽  
2018 ◽  
Vol 360 (6396) ◽  
pp. 1451-1455 ◽  
Author(s):  
M. Z. Mo ◽  
Z. Chen ◽  
R. K. Li ◽  
M. Dunning ◽  
B. B. L. Witte ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Laser Excitation ◽  
Ultrafast Laser ◽  
Atomic Scale ◽  
Melting Transition ◽  
Transition Dynamics ◽  
Melting Regime ◽  
Nonequilibrium States ◽  
Coupling Rate ◽  
Solid Liquid

The ultrafast laser excitation of matters leads to nonequilibrium states with complex solid-liquid phase-transition dynamics. We used electron diffraction at mega–electron volt energies to visualize the ultrafast melting of gold on the atomic scale length. For energy densities approaching the irreversible melting regime, we first observed heterogeneous melting on time scales of 100 to 1000 picoseconds, transitioning to homogeneous melting that occurs catastrophically within 10 to 20 picoseconds at higher energy densities. We showed evidence for the heterogeneous coexistence of solid and liquid. We determined the ion and electron temperature evolution and found superheated conditions. Our results constrain the electron-ion coupling rate, determine the Debye temperature, and reveal the melting sensitivity to nucleation seeds.

From Semiconductor to Metal in a Flash: Observing Ultrafast Laser-Induced Phase Transformations

1997 ◽  
Vol 481 ◽  
Author(s):  
J. P. Callan ◽  
A. M.-T. Kim ◽  
L. Huangt ◽  
E. N. Glezer ◽  
E. Mazur
Keyword(s):  
Phase Transformations ◽  
Dielectric Function ◽  
Spectral Range ◽  
Laser Excitation ◽  
Spectroscopic Technique ◽  
Ultrafast Laser ◽  
Lattice Heating ◽  
Fs Laser

ABSTRACTWe use a new broadband spectroscopic technique to measure ultrafast changes in the dielectric function of a material over the spectral range 1.5–3.5 eV following intense 70-fs laser excitation. The results reveal the nature of the phase transformations which occur in the material following excitation. We studied the response of GaAs and Si. For GaAs, there are three distinct regimes of behavior as the pump fluence is increased — lattice heating, lattice disordering, and a semiconductor-to-metal transition.

scholarly journals Nanotribological Performance Factors for Aqueous Suspensions of Oxide Nanoparticles and Their Relation to Macroscale Lubricity

Lubricants ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 49 ◽  
Author(s):  
Biplav Acharya ◽  
Tyler N. Pardue ◽  
Liangliang Su ◽  
Alex I. Smirnov ◽  
Donald W. Brenner ◽  
...  
Keyword(s):  
Initial Study ◽  
Atomic Scale ◽  
Frictional Drag ◽  
Friction Coefficients ◽  
Materials Properties ◽  
Performance Factors ◽  
Aqueous Suspensions ◽  
Series Of Experiments ◽  
Motional Resistance ◽  
Solid Liquid

Quartz crystal microbalance (QCM) measurements of nanotribological properties of statistically diverse materials combinations of nanoparticles and substrate electrodes in aqueous suspensions are reported and compared to macroscale measurements of the same materials combinations for a subset of the nanoparticle combinations. Four ceramic nanoparticles, TiO2, SiO2, Al2O3, and maghemite (γ-Fe2O3) and ten substrate materials (Au, Al, Cr, Cu, Mo, Ni, Pt, SiO2, Al2O3, and SS304) were studied. The QCM technique was employed to measure frequency and motional resistance changes upon introduction of nanoparticles into the water surrounding its liquid-facing electrode. This series of experiments expanded prior studies that were often limited to a single nanoparticle - solid liquid combination. The variations in QCM response from one nanoparticle to another are observed to be far greater than the variation from one substrate to another, indicating that the nanoparticles play a larger role than the substrates in determining the frictional drag force levels. The results were categorized according to the direction of the frequency and motional resistance changes and candidate statistical performance factors for the datasets were generated. The performance factors were employed to identify associations between the QCM atomic scale results and the macroscale friction coefficient measurements. Macroscale measurements of friction coefficients for selected systems document that reductions (increases) in motional resistance to shear, as measured by the QCM, are linked to decreases (increases) in macroscale friction coefficients. The performance factors identified in the initial study therefore appear applicable to a broader set of statistically diverse samples. The results facilitate full statistical analyses of the data for identification of candidate materials properties or materials genomes that underlie the performance of nanoparticle systems as lubricants.

scholarly journals Creation and Evaluation of Atomically Ordered Side- and Facet-Surface Structures of Three-Dimensional Silicon Nano-Architectures

2020 ◽  
Author(s):  
Azusa N. Hattori ◽  
Ken Hattori
Keyword(s):  
Electron Diffraction ◽  
Surface Science ◽  
Three Dimensional ◽  
Annealing Treatment ◽  
High Energy ◽  
Energy Electron ◽  
Atomic Scale ◽  
Methods Of Evaluation ◽  
Facet Surface ◽  
Microscopy Techniques

The realization of three-dimensional (3D)-architected nanostructures, that is, the transformation from novel two-dimensional (2D) film-based devices to 3D complex nanodevices, is of crucial importance with the progress of scaling down devices to nanometer order. However, little attention has been devoted to controlling the atomic ordering and structures of side-surfaces on 3D structures, while techniques for controlling and investigating 2D surfaces, namely, surface science, have been established only for planar 2D surfaces. We have established an original methodology that enables atomic orderings and arrangements of surfaces with arbitrary directions to be observed on 3D figured structures by developing diffraction and microscopy techniques. An original technique, namely, directly and quantitatively viewing the side- and facet-surfaces at the atomic scale by reflection high-energy electron diffraction (RHEED) and low-energy electron diffraction (LEED), can be used to determine process parameters in etching. This chapter introduces methods of evaluation by RHEED and LEED based on a reciprocal space map and methods of creating various atomically flat 111 and {100} side-surfaces of 3D Si nano-architectures and tilted 111 facet-surfaces fabricated by lithography dry and wet etching processes, followed by annealing treatment in vacuum.

scholarly journals Ruthenium under ultrafast laser excitation: Model and dataset for equation of state, conductivity, and electron-ion coupling

Data in Brief ◽  
2020 ◽  
Vol 28 ◽  
pp. 104980 ◽  
Author(s):  
Yu. Petrov ◽  
K. Migdal ◽  
N. Inogamov ◽  
V. Khokhlov ◽  
D. Ilnitsky ◽  
...  
Keyword(s):  
Equation Of State ◽  
Laser Excitation ◽  
Ultrafast Laser ◽  
Excitation Model

Atomic-Scale Planarization of Single Crystal Diamond Substrates by Ultraviolet Rays Assisted Machining

2010 ◽  
Vol 447-448 ◽  
pp. 66-70 ◽  
Author(s):  
Mutsumi Touge ◽  
Satoru Anan ◽  
Shogo Wada ◽  
Akihisa Kubota ◽  
Yoshitaka Nakanishi ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Low Energy ◽  
Energy Electron ◽  
Atomic Scale ◽  
Polished Surface ◽  
Ultraviolet Rays ◽  
Low Energy Electron Diffraction ◽  
Single Crystal Diamond ◽  
Low Energy Electron

The ultra-precision polishing assisted by the ultraviolet rays irradiation was performed to achieve the atomic-scale planarization of the single crystal diamond substrates. This polishing method is a novel and simple polishing method characterizing by a quartz disk and an ultraviolet irradiation device. The principle three crystal planes of the diamond substrate were polished by this method. The polished surfaces were evaluated by an optical interferometric profilers (Wyko), an atom force microscope (AFM) and LEED (low-energy electron diffraction). The surface roughness of the polished diamond substrates was evaluated as 0.2 ~ 0.4 nmRa in (100), (110) and (111) crystal planes. The LEED (low-energy electron diffraction) patterns indicated the almost perfect crystallographic structure without the residual processed strain beneath the polished surface. In this paper, the optimum polishing condition to achieve the atomic-scale planarization of the diamond substrates has been investigated by the evaluation of LEED patterns, Wyko and AFM images. The mechanismof the ultraviolet rays assisted polishing is discussed in detail.

Atomic-scale imaging of aligned poly-atomic molecules with recollision electron diffraction

2014 ◽  
Author(s):  
Michael G. Pullen ◽  
Benjamin Wolter ◽  
Matthias Baudisch ◽  
Michaël Hemmer ◽  
Arne Senftleben ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Atomic Scale

Investigations using wide-angle electron diffraction on pair ordering mechanisms in FeTb alloys by thermal annealing

1994 ◽  
Vol 52 ◽  
pp. 660-661
Author(s):  
M. Tewes ◽  
J. Zweck ◽  
H. Hoffmann
Keyword(s):  
Electron Diffraction ◽  
Short Range ◽  
Local Density ◽  
Coordination Shell ◽  
Density Fluctuations ◽  
Distribution Functions ◽  
Atomic Scale ◽  
Short Range Ordering ◽  
Isotropic Structure ◽  
Pair Distribution Functions

In our recent work we have shown that electron diffraction is a suitable and precise method to observe short range ordering in various amorphous FeTb alloys by calculating pair distribution functions (PDFs) from these data by means of a fourier inversion. A PDF g(r) is an autocorrelation function of the specimen’s density fluctuations: g(r) = 4πr(ϱ(r) - ϱo) with ϱ(r): autocorrelation of the local density in a distance r, and ϱo macroscopic density of the specimen. The spatial resolution that can be achieved is better than 0.02 nm, and the fine structure of the first coordination shell of the short range order has been described quantitatively with an isotropic structure model. The deviation between calculated and measured PDFs has been about 2%.However, the origin of the uniaxial perpendicular anisotropy in rare earth / transition metal amorphous alloys like FeTb is in general attributed to small anisotropic concentration fluctuations on an atomic scale as introduced in pair ordering, band orientation or stress induced anisotropy models.

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