Spaepen conducts research in the following areas:
> Amorphous materials (metals, semiconductors, polymers): structure, formation, stability, mechanical properties, atomic transport (viscosity, diffusivity, structural relaxation, crystallization)
> Polytetrahedral structure of liquids and quasicrystals
> Thin films and multilayers: preparation, stability, mechanical properties. General effects of size scale on mechanical properties
> Properties of interfaces: crystal/melt, amorphous/crystalline semiconductor, grain boundaries, grain growth, interface tension, interface stress.
> Colloidal systems as analog computers for the study of defects and deformation of crystals and glasses (with D. Weitz)
> Determination of Avogadro's number with an accuracy or better than 10 ppb. Collaboration with metrology laboratories worldwide that are using the silicon single crystal approach. Developing methods to certify the perfection of the silicon to 10 ppb