Dresden 2020 – wissenschaftliches Programm
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HL 28.1: Hauptvortrag
Dienstag, 17. März 2020, 10:00–10:30, ZEU 222
Anisotropic packing in vapor-deposited glasses — •Mark Ediger — University of Wisconsin-Madison, USA
Glasses are generally regarded as highly disordered and the idea of controlling molecular packing in glasses is reasonably met with skepticism. However, as glasses are non-equilibrium materials, a vast array of amorphous structures are possible in principle, even for a single component system. Physical vapor deposition (PVD) allows a surprising amount of control over anisotropic molecular packing in glasses. For organic semiconductors, glasses can be prepared in which the molecules have a substantial tendency to stand-up or lie-down relative to the substrate, and molecular layering can also be achieved. The high density and anisotropic packing of PVD glasses can be explained by a mechanism that is "anti-epitaxial" as structure is templated by the top surface rather than by the underlying substrate. This mechanism implies that similar structures can be prepared by increasing substrate temperature and by decreasing deposition rate, and this has recently been experimentally verified.