Diffraction Properties of a Continuous Random Network Cluster

AbstractUsing fluctuation microscopy, we show that ion-implanted amorphous silicon has more medium-range order than is expected from the continuous random network model. From our previous work on evaporated and sputtered amorphous silicon, we conclude that the structure is paracrystalline, i.e. it possesses crystalline-like order which decays with distance from any point. The observation might pose an explanation for the large heat of relaxation that is evolved by ion-implanted amorphous semiconductors.

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Visualization of tetrahedral disordering in amorphous germanium through local atomic motifs

Journal of Applied Crystallography ◽

10.1107/s1600576718012967 ◽

2018 ◽

Vol 51 (6) ◽

pp. 1544-1550

Author(s):

Aly Rahemtulla ◽

Bruno Tomberli ◽

Stefan Kycia

Keyword(s):

Random Network ◽

Network Models ◽

Refined Model ◽

Amorphous Germanium ◽

Crystalline Materials ◽

X Ray ◽

Alignment Procedure ◽

X Ray Scattering ◽

Structural Details ◽

Continuous Random Network

The atomic arrangements in amorphous solids, unlike those in crystalline materials, remain elusive. The details of atom ordering are under debate even in simplistic random network models. This work presents further advancements in the local atomic motif (LAM) method, first through the introduction of an optimized alignment procedure providing a clearer image of the angular ordering of atoms in a model. Secondly, by applying stereographic projections with LAMs, the angular ordering within coordination shells can be quantified and investigated. To showcase the new capabilities, the LAM method is applied to amorphous germanium, the archetype of covalent amorphous systems. The method is shown to dissect structural details of amorphous germanium (a-Ge) from the continuous random network (CRN) model and a reverse Monte Carlo (RMC) refined model fitted to high-resolution X-ray scattering measurements. The LAMs reveal well defined dihedral ordering in the second shell. The degree of dihedral ordering is observed to be coupled to bond length distances in the CRN model. This coupling is clearly not present within the RMC refined model. The LAMs reveal inclusions of third-shell atoms occupying interstitial positions in the second shell in both models.

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Fluctuation Microscopy in the STEM

Microscopy and Microanalysis ◽

10.1017/s1431927600027203 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 226-227

Author(s):

P. M. Voyles ◽

D. A. Muller

Keyword(s):

Random Network ◽

Dark Field ◽

Distribution Functions ◽

Disordered Materials ◽

Microscopy Technique ◽

Medium Range ◽

Fluctuation Microscopy ◽

Image Position ◽

Continuous Random Network ◽

Vector Magnitude

Fluctuation microscopy is an electron microscopy technique sensitive to medium-range order (MRO) in disordered materials. It has been applied to study amorphous germanium and silicon, leading to the conclusion that these materials exhibit more MRO than the conventional continuous random network model for their structure.As originally proposed by Treacy and Gibson, fluctuation microscopy utilizes mesoscopicresolution (1.5 nm) hollow-cone dark field (HCDF) imaging in a TEM. The normalized variance of such images,is a measure of the magnitude of fluctuations in the diffracted intensity from mesoscopic volumes of the sample and is sensitive to MRO via the three- and four-body atom distribution functions. Studying V as a function of the diffraction vector magnitude k gives information about the degree of MRO and the internal structure of ordered regions. V as a function of the inverse resolution Q gives information about the characteristic MRO length scale.

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Electron and phonon states in an ideal continuous random network model ofa−SiO2glass

Physical Review B ◽

10.1103/physrevb.59.3540 ◽

1999 ◽

Vol 59 (5) ◽

pp. 3540-3550 ◽

Cited By ~ 29

Author(s):

Ming-Zhu Huang ◽

Lizhi Ouyang ◽

W. Y. Ching

Keyword(s):

Network Model ◽

Random Network ◽

Continuous Random Network

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Relaxed continuous random network models (II)

Journal of Non-Crystalline Solids ◽

10.1016/0022-3093(75)90122-2 ◽

1975 ◽

Vol 17 (3) ◽

pp. 299-318 ◽

Cited By ~ 18

Author(s):

J.F. Graczyk ◽

P. Chaudhari

Keyword(s):

Random Network ◽

Network Models ◽

Continuous Random Network

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Relaxed continuous random network models

Journal of Non-Crystalline Solids ◽

10.1016/0022-3093(74)90049-0 ◽

1974 ◽

Vol 15 (2) ◽

pp. 199-214 ◽

Cited By ~ 183

Author(s):

P Steinhardt ◽

R Alben ◽

D Weaire

Keyword(s):

Random Network ◽

Network Models ◽

Continuous Random Network

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Observation of a Continuous Random Network Structure in GexSe100–x Glasses: Results from High-Resolution 77Se MATPASS/CPMG NMR Spectroscopy

The Journal of Physical Chemistry B ◽

10.1021/jp311320t ◽

2013 ◽

Vol 117 (3) ◽

pp. 949-954 ◽

Cited By ~ 31

Author(s):

Derrick C. Kaseman ◽

Ivan Hung ◽

Zhehong Gan ◽

Sabyasachi Sen

Keyword(s):

Nmr Spectroscopy ◽

High Resolution ◽

Network Structure ◽

Random Network ◽

Continuous Random Network

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Structural properties of liquid aluminosilicate with varying Al2O3/SiO2 ratios: Insight from analysis and visualization of molecular dynamics data

Modern Physics Letters B ◽

10.1142/s0217984917500361 ◽

2017 ◽

Vol 31 (05) ◽

pp. 1750036 ◽

Cited By ~ 4

Author(s):

N. V. Yen ◽

M. T. Lan ◽

L. T. Vinh ◽

N. V. Hong

Keyword(s):

Molecular Dynamics ◽

Random Network ◽

Md Simulations ◽

Degree Of Polymerization ◽

Distribution Functions ◽

Molar Ratio ◽

Nonbridging Oxygen ◽

Structural Units ◽

Self Diffusion ◽

Continuous Random Network

Molecular dynamics (MD) simulations and visualizations were explored to investigate the changes in structure of liquid aluminosilicates. The models were constructed for four compositions with varying Al2O3/SiO2 ratio. The local structure and network topology was analyzed through the pair of radial distribution functions, bond angle, bond length and coordination number distributions. The results showed that the structure of aluminosilicates mainly consists of the basic structural units TO[Formula: see text] (T is Al or Si; y = 3, 4, 5). Two adjacent units TO[Formula: see text] are linked to each other through common oxygen atoms and form continuous random network of basic structural units TO[Formula: see text]. The bond statistics (corner-, edge- and face- sharing) between two adjacent TO[Formula: see text] units are investigated in detail. The self-diffusion coefficients for three atomic types are affected by the degree of polymerization (DOP) of network characterized by the proportions of nonbridging oxygen (NBO) and Q[Formula: see text] species in the system. It was found that Q4 and Q3 tetrahedral species (tetrahedron with four and three bridging oxygens, respectively) decreases, while Q0 (with four nonbridging oxygen) increase with increasing Al2O3/SiO2 molar ratio, suggesting that a less polymerized network was formed. The structural and dynamical heterogeneities, micro-phase separation and liquid–liquid phase transition are also discussed in this work.

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