Layered heterostructures integrating two-dimensional materials such as graphene or transition metal dichalcogenides and nanometer-scale layers of inorganic materials are attracting considerable attention since a few years. Organic materials remain however poorly explored in this context, in particular for ultra-thin layers down to the single molecule level. Mixed-dimensional, hybrid heterostructures have a lot to offer in terms of interface physics in fields such as, for instance, polaritonics, excitonics or topological phases and provide new emergent behavior for electronics and optoelectronics.
In this context, vertical organic transistors are promising to outperform the usual performance indicators of horizontal organic thin-film transistors such as transconductance, cut-off frequency and high integration. Up to now, research on this type of devices has mostly focused on vertical organic field-effect transistors. Another type of transistor, the vertical permeable base transistor remains however poorly studied although graphene, as a semi-premeable membrane for electrons, could offer here an exceptional control.
Our main goal with this project is to provide a better fundamental understanding of the interface in hybrid, mixed-dimensional Van der Waals heterostructures with high electronic bandwidth. We will design, fabricate and study vertical heterostructures in the form of organic/graphene/organic stacks and the quality of the organic/graphene interface will be investigated to optimize charge injection through the graphene base. Extensive electrical characterization, from dc up to THz frequencies, and ab-initio simulations will be performed to achieve a deep understanding of these systems. The hybrid design of the proposed structures combining organic materials (organic semiconductors, graphene), metallic contacts and, ultimately, flexible substrates bear a strong potential for application in flexible electronics using the concept of vertical, permeable-base transistor.
The project in organized in three scientific workpackages. (1) We will first focus on the assembly of small molecules and polymer semiconductors with a graphene layer on a substrate. We will characterize the structural and basic electronic properties of this vertical graphene/organic semiconductor interface. (2) A detailed electrical characterization (DC + AC) will then give us access to the physics of this interface and to essential electrical parameters such as the charge transfer between the layers and charge carriers mobility, graphene doping and tunable barrier height parameters. (3) Finally, we will investigate, as a proof of concept, the electronic properties of graphene permeable-base vertical organic transistors.
Monsieur Dominique Vuillaume (Institut d'électronique, de microélectronique et de nanotechnologie)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
EMPA Eidg. Material und Prüfungsanstalt
IEMN Institut d'électronique, de microélectronique et de nanotechnologie
Help of the ANR 197,208 euros
Beginning and duration of the scientific project: January 2019 - 48 Months