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Title: In situ observation of fast surface dynamics during the vapor-deposition of a stable organic glass
By measuring the increments of dielectric capacitance (Δ C ) and dissipation (Δtan  δ ) during physical vapor deposition of a 110 nm film of a molecular glass former, we provide direct evidence of the mobile surface layer that is made responsible for the extraordinary properties of vapor deposited glasses. Depositing at a rate of 0.1 nm s −1 onto a substrate at T dep = 75 K = 0.82 T g , we observe a 2.5 nm thick surface layer with an average relaxation time of 0.1 s, while the glass growing underneath has a high kinetic stability. The level of Δtan  δ continues to decrease for thousands of seconds after terminating the deposition process, indicating a slow aging-like increase in packing density near the surface. At very low deposition temperatures, 32 and 42 K, the surface layer thicknesses and mobilities are reduced, as are the kinetic stabilities.  more » « less
Award ID(s):
1854930
PAR ID:
10248482
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
Soft Matter
Volume:
16
Issue:
48
ISSN:
1744-683X
Page Range / eLocation ID:
10860 to 10864
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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