TY - JOUR
T1 - Origin of Anisotropic Molecular Packing in Vapor-Deposited Alq3 Glasses
AU - Bagchi, Kushal
AU - Jackson, Nicholas E.
AU - Gujral, Ankit
AU - Huang, Chengbin
AU - Toney, Michael F.
AU - Yu, Lian
AU - De Pablo, Juan J.
AU - Ediger, M. D.
N1 - Funding Information:
The experimental work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, Award DE-SC0002161. The authors gratefully acknowledge use of facilities and instrumentation supported by NSF through the University of Wisconsin Materials Research Science and Engineering Center (DMR-1720415). N.E.J. acknowledges support from the Argonne National Laboratory Maria Goeppert Mayer Named Fellowship. We acknowledge the computing resources provided on Blues and Bebop, the high-performance computing clusters operated by the Laboratory Computing Resource Center at Argonne National Laboratory. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515. We thank David Field for helpful discussions.
Publisher Copyright:
© 2018 American Chemical Society.
Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.
PY - 2019/1/17
Y1 - 2019/1/17
N2 - Anisotropic molecular packing is a key feature that makes glasses prepared by physical vapor deposition (PVD) unique materials, warranting a mechanistic understanding of how a PVD glass attains its structure. To this end, we use X-ray scattering and ellipsometry to characterize the structure of PVD glasses of tris(8-hydroxyquinoline) aluminum (Alq3), a molecule used in organic electronics, and compare our results to simulations of its supercooled liquid. X-ray scattering reveals a tendency for molecular layering in Alq3 glasses that depends upon the substrate temperature during deposition and the deposition rate. Simulations reveal that the Alq3 supercooled liquid, like liquid metals, exhibits surface layering. We propose that the layering in Alq3 glasses observed here as well as the previously reported bulk dipole orientation are inherited from the surface structure of the supercooled liquid. This work significantly advances our understanding of the mechanism governing the formation of anisotropic structure in PVD glasses.
AB - Anisotropic molecular packing is a key feature that makes glasses prepared by physical vapor deposition (PVD) unique materials, warranting a mechanistic understanding of how a PVD glass attains its structure. To this end, we use X-ray scattering and ellipsometry to characterize the structure of PVD glasses of tris(8-hydroxyquinoline) aluminum (Alq3), a molecule used in organic electronics, and compare our results to simulations of its supercooled liquid. X-ray scattering reveals a tendency for molecular layering in Alq3 glasses that depends upon the substrate temperature during deposition and the deposition rate. Simulations reveal that the Alq3 supercooled liquid, like liquid metals, exhibits surface layering. We propose that the layering in Alq3 glasses observed here as well as the previously reported bulk dipole orientation are inherited from the surface structure of the supercooled liquid. This work significantly advances our understanding of the mechanism governing the formation of anisotropic structure in PVD glasses.
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U2 - 10.1021/acs.jpclett.8b03582
DO - 10.1021/acs.jpclett.8b03582
M3 - Article
C2 - 30582803
AN - SCOPUS:85060154571
SN - 1948-7185
VL - 10
SP - 164
EP - 170
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 2
ER -