Abstract
We compare experimental fluctuation electron microscopy (FEM) speckle data with electron diffraction simulations for thin amorphous carbon and silicon samples. We find that the experimental speckle intensity variance is generally more than an order of magnitude lower than kinematical scattering theory predicts for spatially coherent illumination. We hypothesize that decoherence, which randomizes the phase relationship between scattered waves, is responsible for the anomaly. Specifically, displacement decoherence can contribute strongly to speckle suppression, particularly at higher beam energies. Displacement decoherence arises when the local structure is rearranged significantly by interactions with the beam during the exposure. Such motions cause diffraction speckle to twinkle, some of it at observable time scales. We also find that the continuous random network model of amorphous silicon can explain the experimental variance data if displacement decoherence and multiple scattering is included in the modeling. This may resolve the longstanding discrepancy between X-ray and electron diffraction studies of radial distribution functions, and conclusions reached from previous FEM studies. Decoherence likely affects all quantitative electron imaging and diffraction studies. It likely contributes to the so-called Stobbs factor, where high-resolution atomic-column image intensities are anomalously lower than predicted by a similar factor to that observed here.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1455-1474 |
| Number of pages | 20 |
| Journal | Microscopy and Microanalysis |
| Volume | 21 |
| Issue number | 6 |
| DOIs | |
| State | Published - 2015 |
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Keywords
- amorphous materials
- continuous random network
- decoherence
- Fluctuation electron microscopy
- medium-range order
ASJC Scopus subject areas
- Instrumentation
Cite this
Speckle Suppression by Decoherence in Fluctuation Electron Microscopy. / Rezikyan, Aram; Jibben, Zechariah J.; Rock, Bryan A.; Zhao, Gongpu; Koeck, Franz A M; Nemanich, Robert; Treacy, Michael.
In: Microscopy and Microanalysis, Vol. 21, No. 6, 2015, p. 1455-1474.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Speckle Suppression by Decoherence in Fluctuation Electron Microscopy
AU - Rezikyan, Aram
AU - Jibben, Zechariah J.
AU - Rock, Bryan A.
AU - Zhao, Gongpu
AU - Koeck, Franz A M
AU - Nemanich, Robert
AU - Treacy, Michael
PY - 2015
Y1 - 2015
N2 - We compare experimental fluctuation electron microscopy (FEM) speckle data with electron diffraction simulations for thin amorphous carbon and silicon samples. We find that the experimental speckle intensity variance is generally more than an order of magnitude lower than kinematical scattering theory predicts for spatially coherent illumination. We hypothesize that decoherence, which randomizes the phase relationship between scattered waves, is responsible for the anomaly. Specifically, displacement decoherence can contribute strongly to speckle suppression, particularly at higher beam energies. Displacement decoherence arises when the local structure is rearranged significantly by interactions with the beam during the exposure. Such motions cause diffraction speckle to twinkle, some of it at observable time scales. We also find that the continuous random network model of amorphous silicon can explain the experimental variance data if displacement decoherence and multiple scattering is included in the modeling. This may resolve the longstanding discrepancy between X-ray and electron diffraction studies of radial distribution functions, and conclusions reached from previous FEM studies. Decoherence likely affects all quantitative electron imaging and diffraction studies. It likely contributes to the so-called Stobbs factor, where high-resolution atomic-column image intensities are anomalously lower than predicted by a similar factor to that observed here.
AB - We compare experimental fluctuation electron microscopy (FEM) speckle data with electron diffraction simulations for thin amorphous carbon and silicon samples. We find that the experimental speckle intensity variance is generally more than an order of magnitude lower than kinematical scattering theory predicts for spatially coherent illumination. We hypothesize that decoherence, which randomizes the phase relationship between scattered waves, is responsible for the anomaly. Specifically, displacement decoherence can contribute strongly to speckle suppression, particularly at higher beam energies. Displacement decoherence arises when the local structure is rearranged significantly by interactions with the beam during the exposure. Such motions cause diffraction speckle to twinkle, some of it at observable time scales. We also find that the continuous random network model of amorphous silicon can explain the experimental variance data if displacement decoherence and multiple scattering is included in the modeling. This may resolve the longstanding discrepancy between X-ray and electron diffraction studies of radial distribution functions, and conclusions reached from previous FEM studies. Decoherence likely affects all quantitative electron imaging and diffraction studies. It likely contributes to the so-called Stobbs factor, where high-resolution atomic-column image intensities are anomalously lower than predicted by a similar factor to that observed here.
KW - amorphous materials
KW - continuous random network
KW - decoherence
KW - Fluctuation electron microscopy
KW - medium-range order
UR - http://www.scopus.com/inward/record.url?scp=84994578260&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84994578260&partnerID=8YFLogxK
U2 - 10.1017/S1431927615015135
DO - 10.1017/S1431927615015135
M3 - Article
VL - 21
SP - 1455
EP - 1474
JO - Microscopy and Microanalysis
JF - Microscopy and Microanalysis
SN - 1431-9276
IS - 6
ER -