Hydrogen-Induced Reduction in Medium Range Order of a-Si Thin Films Observed using Fluctuation Electron Microscopy

2004 ◽  
Vol 10 (S02) ◽  
pp. 802-803
Author(s):  
Lakshmi Narayana Nittala ◽  
Sreenivas Jayaraman ◽  
Brent A Sperling ◽  
John R Abelson
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Range Order ◽  
Medium Range Order ◽  
Medium Range ◽  
Fluctuation Electron Microscopy

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Fluctuation Electron Microscopy Study of Medium-Range Packing Order in Ultrastable Indomethacin Glass Thin Films

2015 ◽  
Vol 1757 ◽  
Author(s):  
L. He ◽  
A. Gujral ◽  
M. D. Ediger ◽  
P. M. Voyles
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Beam Current ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Range Order ◽  
Total Electron ◽  
Medium Range Order ◽  
Medium Range ◽  
Fluctuation Electron Microscopy

ABSTRACTWe have used fluctuation electron microscopy (FEM) to measure the medium range order in the molecular packing of 40 nm thick indomethacin glass films. Vapor deposition of indomethacin can create glasses with extraordinary kinetic stability and high density. We find peaks in the FEM variance at diffraction vector magnitudes between 0.03 and 0.09 Å-1, corresponding to intermolecular packing distances of 1-3 nm. FEM experiments were performed with a 13 nm diameter electron probe, so these data are sensitive to medium-range order in intermolecular packing. The FEM variance from an indomethacin glass with normal stability cooled from the liquid is significantly smaller than the variance from the ultrastable glass, suggesting that ultrastable glass is more structurally heterogeneous at a 13 nm length scale. A dose of ∼7×105 e-/nm2 with a very low beam current of ∼ 2.5 pA at 200 kV was used to minimize electron beam damage to the sample, and the average electron diffraction from the sample is unchanged at total electron doses fourteen times larger than required for a FEM experiment. These preliminary results on medium-range order in molecular glasses suggest that we may be able to provide insight into the structural differences between the remarkable ultrastable thin films and ordinary glasses.

Evidence from Simulations for Orientational Medium Range Order in Fluctuation-Electron-Microscopy Observations of a-Si

2004 ◽  
Vol 10 (S02) ◽  
pp. 820-821 ◽  
Author(s):  
Sanjay V. Khare ◽  
Serge M. Nakhmanson ◽  
Paul M. Voyles ◽  
Pawel Keblinski ◽  
John R. Abelson
Keyword(s):  
Electron Microscopy ◽  
Range Order ◽  
Medium Range Order ◽  
Medium Range ◽  
Fluctuation Electron Microscopy

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Medium-Range Order in High Al-content Amorphous Alloys Measured by Fluctuation Electron Microscopy

2003 ◽  
Vol 806 ◽  
Author(s):  
W. G. Stratton ◽  
J. Hamann ◽  
J. H. Perepezko ◽  
P. M. Voyles
Keyword(s):  
Electron Microscopy ◽  
Cold Rolling ◽  
Amorphous Alloys ◽  
Melt Spinning ◽  
Amorphous State ◽  
Structural Difference ◽  
Range Order ◽  
Medium Range Order ◽  
Medium Range ◽  
Fluctuation Electron Microscopy

ABSTRACTWe have used fluctuation electron microscopy (FEM) to measure nanoscale mediumrange order in amorphous Al92Sm8. Samples of this amorphous alloy formed by rapid quenching (melt-spinning) show a high density of pure Al nanocrystals (>1020 m-3) after low temperature (< 250 °C) devitrification. In samples amorphized by deformation (cold-rolling), primary Al-crystallization does not occur. This difference in devitrification behavior suggests an underlying structural difference in the amorphous state. FEM is a quantitative microscopy technique for determining nanoscale medium-range order in amorphous materials. Our measurements show that amorphous alloys formed by melt-spinning and cold-rolling have significant structural differences, and that annealing melt-spun alloy under conditions previously shown to modify the devitrification thermodynamics also changes the medium-range structure.

Observations of structural order in ion-implanted amorphous silicon

2001 ◽  
Vol 16 (11) ◽  
pp. 3030-3033 ◽  
Author(s):  
Ju-Yin Cheng ◽  
J. M. Gibson ◽  
D. C. Jacobson
Keyword(s):  
Electron Microscopy ◽  
Amorphous Silicon ◽  
Random Network ◽  
Dark Field ◽  
Range Order ◽  
Length Scale ◽  
Medium Range Order ◽  
Medium Range ◽  
Fluctuation Electron Microscopy ◽  
Ion Implanted

Medium-range order in ion-implanted amorphous silicon has been observed using fluctuation electron microscopy. In fluctuation electron microscopy, variance of dark-field image intensity contains the information of high-order atomic correlations, primarily in medium-range order length scale (1–3 nm). Thermal annealing greatly reduces the order and leaves a random network. It appears that the free energy change previously observed on relaxation may therefore be associated with randomization of the network. In this paper, we discuss the origin of the medium-range order during implantation, which can be interpreted as a paracrystalline state, that is, a disordered network enclosing compacts of highly topologically ordered grains on the length scale of 1–3 nm with significant strain fields.

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