Size analysis of nanoscale order in amorphous materials by variable-resolution fluctuation electron microscopy

Bogle, Stephanie N.; Nittala, Lakshmi N.; Twesten, R. D.; Voyles, Paul M.; Abelson, John R.

doi:10.1016/j.ultramic.2010.05.001

Cited by 42 publications

(46 citation statements)

References 23 publications

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“…In these experiments, qualitative differences in FEM variance were observed and attributed to fundamental physical phenomena such as differences in film deposition condition [23], the existence and thermal ripening of subcritical nuclei that precede crystallisation [29,30], and the effect of alloying on crystallisation kinetics [33]. Quantitative FEM analysis has thus far proven challenging, but with recent developments such as variable resolution FEM, information about the extent of the nanometre-scale ordering can be extracted [26,34]. Nevertheless, a number of recent studies have been successful in relating the scattering covariance and angular correlations in FEM data to structural information [13,35,36].…”

Section: Introductionmentioning

confidence: 99%

Medium range structural order in amorphous tantala spatially resolved with changes to atomic structure by thermal annealing

Hart

Bassiri

Borisenko

et al. 2016

Journal of Non-Crystalline Solids

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International audienceAmorphous tantala (a-Ta2O5) is an important technological material that has wide ranging applications in electronics, optics and the biomedical industry. It is used as the high refractive index layers in the multi-layer dielectric mirror coatings in the latest generation of gravitational wave interferometers, as well as other precision interferometers. One of the current limitations in sensitivity of gravitational wave detectors is Brownian thermal noise that arises from the tantala mirror coatings. Measurements have shown differences in mechanical loss of the mirror coatings, which is directly related to Brownian thermal noise, in response to thermal annealing. We utilise scanning electron diffraction to perform a modified version of Fluctuation Electron Microscopy (FEM) on Ion Beam Sputtered (IBS) amorphous tantala coatings, definitively showing an increase in the medium range order (MRO), as determined from the variance between the diffraction patterns in the scan, due to thermal annealing at increasing temperatures. Moreover, we employ Virtual Dark-Field Imaging (VDFi) to spatially resolve the FEM signal, enabling investigation of the persistence of the fragments responsible for the medium range order, as well as the extent of the ordering over nm length scales, and show ordered patches larger than 5 nm in the highest temperature annealed sample. These structural changes directly correlate with the observed changes in mechanical loss. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

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Section: Introductionmentioning

confidence: 99%

Medium range structural order in amorphous tantala spatially resolved with changes to atomic structure by thermal annealing

Hart

Bassiri

Borisenko

et al. 2016

Journal of Non-Crystalline Solids

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“…Several approaches have been suggested. Bogle et al [4] observed a correlation between the relative heights of the first and second variance peak, at least for Si, but this depends also on the probe size. Yi et al [16] proposed detailed fitting of peak heights and probe size, based on a reasonably sophisticated dispersed crystal model of a composite, but this appears vulnerable to details of the structure (e.g.…”

Section: ) Volume Fraction Of Ordered Regionsmentioning

confidence: 99%

“…Using the "ansatz" model proposed by Gibson et al [3], several authors have had consistent results in measuring the correlation length from the dependence of the normalized intensity variance on the probe size (also known as "variable resolution microscopy") e.g. Bogle et al [4]. There has been controversy about the volume fraction.…”

Section: Introductionmentioning

confidence: 99%

“…Gibson et al [3] proposed an "ansatz" model for the measurement of the correlation length, the validity of which has repeatedly been demonstrated experimentally and by simulation e.g. [4,13]. The ansatz model approximates the simulation of variance by assuming that the contributions arising from probe size (beam convergence) and scattering vector are decoupled -literally, a separation of variables where we declare that V (rp, k) ≡ R (rp) K (k).…”

Section: Introductionmentioning

confidence: 99%

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Fluctuation microscopy analysis of amorphous silicon models

Gibson

Treacy

2017

Ultramicroscopy

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Using computer-generated models we discuss the use of fluctuation electron microscopy (FEM) to identify the structure of amorphous silicon. We show that a combination of variable resolution FEM to measure the correlation length, with correlograph analysis to obtain the structural motif, can pin down structural correlations. We introduce the method of correlograph variance as a promising means of independently measuring the volume fraction of a paracrystalline composite. From comparisons with published data, we affirm that only a composite material of paracrystalline and continuous random network that is substantially paracrystalline could explain the existing experimental data, and point the way to more precise measurements on amorphous semiconductors. The results are of general interest for other classes of disordered materials.

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“…The most important difference is that the resolution in the nanodiffraction mode can easily be changed by modifying the diameter of the nanoprobe (the variable resolution mode), whereas the resolution in the dark-field mode is fixed by the size of the objective aperture. [16] Data obtained at multiple resolutions give explicit information about the length scale of structural order, as discussed in Section 4. Another difference is that, although the two modes of FTEM give the same shape of V(k), the nanodiffraction mode gives higher magnitude of variance.…”

Section: Nanodiffraction and Variable Resolution Modesmentioning

confidence: 99%

Fluctuation Transmission Electron Microscopy: Detecting Nanoscale Order in Disordered Structures

2010

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The structures of many disordered materials are not ideally random, but contain structural order on the scale of 1-3 nm. However, such nanoscale order, called medium-range order, cannot be detected by conventional diffraction methods in most cases. Fluctuation transmission electron microscopy (FTEM) has the capability to detect medium-range order in disordered materials based on statistical analysis of nanodiffraction patterns or dark-field images from TEM. FTEM has been successful in demonstrating the theoretically predicted development of nanoscale nuclei in amorphous chalcogenides, as well as in revealing the subtle effect of different preparation routes on the medium-range order in amorphous semiconductors and metals. The fluctuation principle can also be applied to study structural order on longer length scales in polymers and other disordered materials using X-rays or visible light. Further advances in theory and practice of FTEM will greatly increase our understanding of amorphous structures and nucleation phenomena.

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Size analysis of nanoscale order in amorphous materials by variable-resolution fluctuation electron microscopy

Cited by 42 publications

References 23 publications

Medium range structural order in amorphous tantala spatially resolved with changes to atomic structure by thermal annealing

Medium range structural order in amorphous tantala spatially resolved with changes to atomic structure by thermal annealing

Fluctuation microscopy analysis of amorphous silicon models

Fluctuation Transmission Electron Microscopy: Detecting Nanoscale Order in Disordered Structures

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