G. Galeotti, PhD - Projects & Publications

The realization of few-layer thick nano-devices is one of the great challenges of today nanotechnology. The need for constant miniaturization has however introduced new criticality that may break the electronics = silicon equation. A possible solution could be to use graphene as an active element, since it is a natural one-layer thick material, with high electron mobility. The downside of graphene is however its zero bandgap, which limits its possible applications. This led to the study of graphene-like materials, i.e. 2D polymers with tunable properties, grown through bottom-up approaches. The goal is to use the molecule-molecule and molecule-substrate interactions to directly self-assemble the wanted structure, and to further manipulate them into extended polymer with the right architecture and tailoring possibilities. Various reactions have been used to achieve this goal, but the most successful one is the Ullmann coupling, a two-step reaction in which aryl halides forms organometallic species in the first step and π-conjugated polymers in the latter. Despite the large number of studies, there are still open questions, and the choice of the building block was found to be pivotal to obtaining extended nanostructures with the wanted properties.

Outline of the project to realize devices using 2D conjugated polymers as active components: First the right building block is selected and synthesized (a), and 1D and 2D polymers are obtained using metallic surfaces as templates (b). In a second step, the optoelectronic properties of the polymers are studied and compared with the theoretical ones (c), before moving the material onto Si substrates, where devices are realized (d).

My goal is to advance the understanding of both molecular interaction and the mechanism of the Ullmann coupling, starting from the building block up to the realization of the low-dimension polymer, addressing the problems to overcome and how to characterize the final material properties, before moving on to tackle the realization of real-life devices.

The project I've worked at the Deutsches Museum involved the direct deposition of radical species instead of intact molecules, to remove the need for reactive surfaces, and open the door to a pletora of inert and insulating surfaces. To do so we developed a Radical Deposition Source.