Using 4D STEM to probe mesoscale order in molecular glass films prepared by physical vapor deposition

Abstract

Physical vapor deposition can be used to prepare highly stable organic glass systems where the molecules show orientational and translational ordering at the nanoscale. We have used low-dose four-dimensional scanning transmission electron microscopy (4D STEM), enabled by a fast direct electron detector, to map columnar order in glassy samples of a discotic mesogen using a 2 nm probe. Both vapor deposited and liquid cooled glassy films show domains of similar orientation, but their size varies from tens to hundreds of nanometers, depending on processing. Domain sizes are consistent with surface diffusion mediated ordering during film deposition. These results demonstrate the ability of low-dose 4D STEM to characterize mesoscale structure in a molecular glass system which may be relevant to organic electronics.

References in corpus (3)

• Controlling Structure and Properties of Vapor-Deposited Glasses of Organic Semiconductors: Recent Advances and Challenges
• Using Deposition Rate and Substrate Temperature to Manipulate Liquid Crystal-like Order in a Vapor-deposited Hexagonal Columnar Glass
• Seeing Structural Evolution of Organic Molecular Nano-crystallites Using 4D Scanning Confocal Electron Diffraction

Cited by in corpus (1)

• Vapor-to-glass preparation of biaxially aligned organic semiconductors