22 September

Ground state charge transfer phenomena for controlling energy levels of semiconductor heterojunctions

Thursday 22 September 2022, 03:00pm

ICN2 Seminar Room, Campus UAB, Bellaterra, Barcelona

Nanoseminar in Physics

SpeakerProf. Norbert Koch, Institut für Physik, Humboldt-Universität zu Berlin, Germany / Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany

Abstract: The realization of electronic and optoelectronic devices with superior functionality and efficiency relies on the ability to tailor the electronic energy levels of the utilized materials and their heterojunctions. The key prerequisite for this is a comprehensive understanding of the materials’ intrinsic properties and their physicochemical interactions at interfacial interactions. For many inorganic and organic semiconductors pertinent knowledge has been acquired, and several opportunities to tune the energy level alignment at inorganic/organic semiconductor junctions are available. After a brief reminder of a few specifics of the two materials classes, modern approaches for energy level tuning are explained, and their capability to span a tuning-range of presently up to 3 eV is exemplified.

Another attractive material class, particularly for reaching the ultimate miniaturization of devices, are two-dimensional semiconductors in the monolayer limit, such as transition metal dichalcogenides (TMDCs). Studying their intrinsic electronic properties on insulating substrates with photoelectron spectroscopy is a major challenge, which has meanwhile been mastered. This enabled disentangling the fundamental substrate-dependent ground state charge transfer phenomena between TMDCs and molecular electron acceptors towards doping. These will be discussed, as well as a recently found pronounced temperature-dependence of charge transfer in a three-component van der Waals heterostructure.

Introductory talk: "Nanocalorimetry and AFM as unique tools for a direct and visual evidence of dynamic heterogeneity in thin film organic glasses” by Dr. Cristian Rodríguez-Tinoco, UAB Senior Researcher at Group of Thermal Properties of Nanoscale Materials - GTNaM. 

After the seminar, a coffee service will be available at the room for attendees.