One of the main driving forces of the ongoing nanotechnology revolution is the ever-improving ability to understand and control the properties of quantum matter even down to the atomic scale. Key drivers of this revolution are layered materials such as transition metal dichalcogenides (TMD). The realisation of novel TMD-based electronic devices relies heavily on understanding the relation between their structural and electrical properties at the nanoscale. Crucially, one-dimensional (1D) TMDs have been predicted to exhibit striking functionalities including metallic edge states, ferromagnetic behaviour, and mobilities that are not suppressed as compared to their 2D counterparts. Indeed, in the 1D nanoscale limit, the lateral edges of TMDs become dominant, opening novel opportunities to tune edge-induced electrical properties leading to i.e. enhanced charge carrier mobility. However, these predictions for novel phenomena in 1D TMDs lack experimental verification, due to the challenge in accessing the relevant information at the nanoscale.
This proposal will provide input towards novel quantum technologies for developing low-energy consumption tunable electronics, efficient signal processing and quantum computation. These applications are directly relevant to address important societal challenges, such as to reduce the energy demand of the computing and IT sectors.
The overall objective of the project is to unravel the interplay between structural and electrical edge-induced properties by exploiting recent breakthroughs in electron microscopy (EM) allowing simultaneous unprecedented spatial and spectral resolution. I will focus on MoS2 nanoribbons, and use electron-energy loss spectroscopy to map the electronic properties at the nanometer scale. Beyond the optimization of EM for 1D TMD characterization, I will investigate semiconducting-to metal and ferromagnetic transitions by realising controllable edge structures. Specifically, the two main goals of the project can be classified as follows:
a. Inducing novel functionalities in 1D TMDs by tuning edge structure configurations. Here the aim is to investigate how the electronic and magnetic states are modified through controllable edge structures (AC, ZZ, and their combination), chemical functionalization and vacancy-induced localized gap states.
b. Mapping the interplay between edge-induced structural, electric, and magnetic properties of 1D TMDs. The goal is to pin down the unique physical properties of the edges of 1D ZZ (AC) MoS2 nanoribbons such as metallic edge states, the tunable band gap, and the ferromagnetic order. This will be achieved by optimizing low-voltage electron energy-loss spectroscopy (EELS) measurements, including momentum-resolved EELS, to access the local band structures and dispersion relations within nanoscale volumes.
