Quantifying nanoscale order in amorphous materials via scattering covariance in fluctuation electron microscopy

Tian T. Li, Kristof Darmawikarta, John R. Abelson

Research output: Contribution to journalArticle

Abstract

Fluctuation Transmission Electron Microscopy (FTEM) has a unique ability to probe topological order on the 1-3nm length scale in diffraction amorphous materials. However, extracting a quantitative description of the order has been challenging. We report that the FTEM covariance, computed at two non-degenerate Bragg reflections, is able to distinguish different regimes of size vs. volume fraction of order. The covariance analysis is general and does not require a material-specific atomistic model. We use a Monte-Carlo approach to compute different regimes of covariance, based on the probability of exciting multiple Bragg reflections when a STEM nanobeam interacts with a volume containing ordered regions in an amorphous matrix. We perform experimental analysis on several sputtered amorphous thin films including a-Si, nitrogen-alloyed GeTe and Ge2Sb2Te5. The samples contain a wide variety of ordered states. Comparison of experimental data with the covariance simulation reveals different regimes of nanoscale topological order.

Original languageEnglish (US)
Pages (from-to)95-100
Number of pages6
JournalUltramicroscopy
Volume133
DOIs
StatePublished - Oct 1 2013

Keywords

  • Fluctuation Transmission Electron Microscopy
  • Nanoscale order
  • Scattering
  • Statistics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Instrumentation

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