Accessing electron-phonon interactions of two-dimensional metal organic frameworks by ultrabroadband terahertz spectroscopy based on the spintronic trilayer emitter
The recent discovery of high-mobility band-like charge transport in two-dimensional semiconducting Metal Organic Frameworks (2D-MOFs), represents a breakthrough that paves the way for developing novel highly tailorable optoelectronic devices. However, for harvesting the benefits of these materials, it is still required a deeper understanding on the interplay between MOF structure and chemical composition with electronic structure, conductivity, doping and charge carrier mobility. Among the current methods used to characterize charge transport in MOFs, Time-Resolved Terahertz (THz) Spectroscopy (TRTS) stands out, owing to the fact that it is a non-contact technique, with sub-ps resolution, and capable of disentangling the conductivity, doping and mobility of a given sample in the AC limit. Despite powerful, current TRTS setups do have a limitation connected with a small frequency bandwidth of state-of-the-art THz probes (typically limited to 0.2-2 THz). In this project, I will introduce a novel THz Spintronic Trilayer Emitter (STE), holding a bandwidth that is ~15 times broader than that of traditional THz sources, for investigating charge transport in the recently discovered semiconducting MOFs. The STE ultrabroadband frequency window, linked to an ultrashort pulse time duration, will allow for the first time characterizing phonons and their interplay with free carriers (which limit sample´s mobility) as a function of sample chemistry and structure. This powerful approach will ultimately lead to unequivocally establishing connections between structure and charge transport properties in these promising and technologically relevant materials.