scholarly journals Surface mobility in amorphous selenium and comparison with organic molecular glasses

2021 ◽  
Vol 154 (7) ◽  
pp. 074703
Author(s):  
Jaroslav Barták ◽  
Jirí Málek ◽  
Kushal Bagchi ◽  
M. D. Ediger ◽  
Yuhui Li ◽  
...  
Keyword(s):  
Amorphous Selenium ◽  
Molecular Glasses ◽  
Surface Mobility

scholarly journals Polyamorphism of vapor-deposited amorphous selenium in response to light

2020 ◽  
Vol 117 (39) ◽  
pp. 24076-24081 ◽  
Author(s):  
Aixi Zhang ◽  
Yi Jin ◽  
Tianyi Liu ◽  
Richard B. Stephens ◽  
Zahra Fakhraai
Keyword(s):  
White Light ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Amorphous Solid ◽  
Amorphous Selenium ◽  
Light Illumination ◽  
Surface Mobility ◽  
Stable Glasses ◽  
Enhanced Mobility ◽  
Substrate Temperatures

Enhanced surface mobility is critical in producing stable glasses during physical vapor deposition. In amorphous selenium (a-Se) both the structure and dynamics of the surface can be altered when exposed to above-bandgap light. Here we investigate the effect of light on the properties of vapor-deposited a-Se glasses at a range of substrate temperatures and deposition rates. We demonstrate that deposition both under white light illumination and in the dark results in thermally and kinetically stable glasses. Compared to glasses deposited in the dark, stable a-Se glasses formed under white light have reduced thermal stability, as measured by lower density change, but show significantly improved kinetic stability, measured as higher onset temperature for transformation. While light induces enhanced mobility that penetrates deep into the surface, resulting in lower density during vapor deposition, it also acts to form more networked structures at the surface, which results in a state that is kinetically more stable with larger optical birefringence. We demonstrate that the structure formed during deposition with light is a state that is not accessible through liquid quenching, aging, or vapor deposition in the dark, indicating the formation of a unique amorphous solid state.

Diffraction from arrays of antiphase boundaries in ordered III-V alloys

1987 ◽  
Vol 45 ◽  
pp. 312-313
Author(s):  
T. S. Kuan
Keyword(s):  
High Surface ◽  
Growth Conditions ◽  
Ternary Alloys ◽  
Local Growth ◽  
Antiphase Boundaries ◽  
Surface Mobility ◽  
Ordered Phases ◽  
Diffraction Patterns ◽  
Atomically Flat ◽  
Degree Of Order

Recent electron diffraction studies have found ordered phases in AlxGa1-xAs, GaAsxSb1-x, and InxGa1-xAs alloy systems, and these ordered phases are likely to be found in many other III-V ternary alloys as well. The presence of ordered phases in these alloys was detected in the diffraction patterns through the appearance of superstructure reflections between the Bragg peaks (Fig. 1). The ordered phase observed in the AlxGa1-xAs and InxGa1-xAs systems is of the CuAu-I type, whereas in GaAsxSb1-x this phase and a chalcopyrite type ordered phase can be present simultaneously. The degree of order in these alloys is strongly dependent on the growth conditions, and during the growth of these alloys, high surface mobility of the depositing species is essential for the onset of ordering. Thus, the growth on atomically flat (110) surfaces usually produces much stronger ordering than the growth on (100) surfaces. The degree of order is also affected by the presence of antiphase boundaries (APBs) in the ordered phase. As shown in Fig. 2(a), a perfectly ordered In0.5Ga0.5As structure grown along the <110> direction consists of alternating InAs and GaAs monolayers, but due to local growth fluctuations, two types of APBs can occur: one involves two consecutive InAs monolayers and the other involves two consecutive GaAs monolayers.

Ultra high resolution SEM at high voltage images individual fab fragments applied as molecular label to cell surface receptors

1989 ◽  
Vol 47 ◽  
pp. 70-71
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Resolution ◽  
High Energy ◽  
Metal Coating ◽  
Beam Diameter ◽  
Surface Receptors ◽  
Surface Mobility ◽  
Metal Atoms ◽  
Shadowing Effect ◽  
Imaging Mode ◽  
Deposition Techniques

Topographic ultra high resolution can now routinely be established on bulk samples in cold field emission scanning electron microscopy with a second generation of microscopes (FSEM) designed to provide 0.5 nm probe diameters. If such small probes are used for high magnification imaging, topographic contrast is so high that remarkably fine details can be imaged on 2DMSO/osmium-impregnated specimens at ribosome surfaces even without a metal coating. On TCH/osmium-impregnated specimens topographic resolution can be increased further if the SE-I imaging mode is applied. This requires that beam diameter and metal coating thickness be made smaller than the SE range of ~1 nm and background signal contributions be reduced. Subnanometer small probes can be obtained (only) at high accelerating voltages. Subnanometer thin continuous metal films can be produced under the following conditions: self-shadowing effect between metal atoms must be reduced through appropriate deposition techniques and surface mobility of metal atoms must be diminished through high energy sputtering and/or specimen cooling.

Light-induced changes in amorphous selenium films containing Sb additives

1999 ◽  
Vol 4 (0) ◽  
pp. 99-101
Author(s):  
V. I. Mikla ◽  
I. P. Mikhalko ◽  
V. V. Mikla ◽  
Yu. Yu. Nagy
Keyword(s):  
Amorphous Selenium ◽  
Selenium Films ◽  
Induced Changes

Interpretation of infrared spectra of chalcogenide glasses Se95As5 impurited by samarium

2015 ◽  
Vol 11 (1) ◽  
pp. 2914-2917
Author(s):  
Alekberov R.I ◽  
Mekhtiyeva S.I ◽  
Isayev A.I ◽  
Mammadova H.I.
Keyword(s):  
Infrared Spectra ◽  
Chalcogenide Glasses ◽  
Amorphous Selenium ◽  
Structural Elements

In work investigated with method IR of spectroscopy of amorphous selenium andsystem Se95As5 containing impurity samarium. It is certain that, in IR a spectrum of amorphous selenium due to hypervalent defects maxima with different intensity are observed in 230 and 270 cm-1.Increase of the concentration of impurity samarium in spectrum Se95As5, the maximum arises with 400cm-1frequency which, are connected with SmSe3 structural elements.

High Autonomy Lunar Surface Mobility Systems

2006 ◽  
Author(s):  
Ernesto Vallerani ◽  
Alberto Della Torre ◽  
Gian Paolo Guizzo ◽  
Igor Vukman
Keyword(s):  
Lunar Surface ◽  
Surface Mobility

Threshold and memory switching in amorphous selenium thin films

1979 ◽  
Vol 53 (1) ◽  
pp. 339-350 ◽  
Author(s):  
G. Jones ◽  
R. A. Collins
Keyword(s):  
Thin Films ◽  
Amorphous Selenium ◽  
Memory Switching

scholarly journals Erratum to: Hierarchical aging pathways and signatures of thermodynamic transition in molecular glasses

2020 ◽  
Vol 64 (1) ◽  
pp. 266-266
Author(s):  
Shiyu Liu ◽  
Yao Yu ◽  
Lin Liu ◽  
Yue Wu
Keyword(s):  
Molecular Glasses

scholarly journals Autonomy for Space Robots: Past, Present, and Future

2021 ◽  
Author(s):  
Issa A.D. Nesnas ◽  
Lorraine M. Fesq ◽  
Richard A. Volpe
Keyword(s):  
Space Exploration ◽  
System Level ◽  
Physical Interaction ◽  
Data Handling ◽  
Proximity Operations ◽  
The Past ◽  
Surface Mobility ◽  
Spacecraft Navigation ◽  
New Frontier ◽  
Near Earth Objects

Abstract Purpose of Review The purpose of this review is to highlight space autonomy advances across mission phases, capture the anticipated need for autonomy and associated rationale, assess state of the practice, and share thoughts for future advancements that could lead to a new frontier in space exploration. Recent Findings Over the past two decades, several autonomous functions and system-level capabilities have been demonstrated and used in spacecraft operations. In spite of that, spacecraft today remain largely reliant on ground in the loop to assess situations and plan next actions, using pre-scripted command sequences. Advances have been made across mission phases including spacecraft navigation; proximity operations; entry, descent, and landing; surface mobility and manipulation; and data handling. But past successful practices may not be sustainable for future exploration. The ability of ground operators to predict the outcome of their plans seriously diminishes when platforms physically interact with planetary bodies, as has been experienced in two decades of Mars surface operations. This results from uncertainties that arise due to limited knowledge, complex physical interaction with the environment, and limitations of associated models. Summary Robotics and autonomy are synergistic, wherein robotics provides flexibility, autonomy exercises it to more effectively and robustly explore unknown worlds. Such capabilities can be substantially advanced by leveraging the rapid growth in SmallSats, the relative accessibility of near-Earth objects, and the recent increase in launch opportunities.

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