Nanoseminar in Chemistry and Materials

IN-PERSON EVENT, REGISTER HERE to attend

Speaker: Prof. Mark Ediger,  University of Wisconsin-Madison, US

Abstract: Glasses are generally regarded as 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. Physical vapor deposition (PVD) produces glasses with properties that cannot be achieved by other preparation routes, including high stability and controlled anisotropy. The exotic properties of PVD glasses can be explained by a surface equilibration mechanism: mobility near the free surface allows partial equilibration during deposition.

The active layers in commercial OLEDs are PVD glasses of organic semiconductors, and to connect with the device community, much of our current work involves organic semiconductors. For these systems, we have shown that highly stable glasses resist crystallization. We can control molecular orientation in both thick films, and the ~10 nm films used in OLEDS. Very recently, we have succeeded in measuring molecular orientation with sub-nm resolution at the interface between two vapor-deposited organic semiconductors. These experiments utilize ellipsometry, grazing-incidence x-ray scattering, and polarized soft x-ray reflectivity.  

Hosted by Prof. Javier Rodríguez Viejo, Thermal Properties of Nanoscale Materials Group Leader at ICN2