The research group of B. Hackens focuses on understanding electron transport in nanodevices and nanomaterials at the local scale, mainly using scanning probe techniques. Nanodevices are mainly fabricated from high mobility 2D carrier systems hosted in semiconductor heterostructures, or in 2D crystals, including graphene. Different themes are investigated related to transport properties of nanodevices, and in particular coherent and ballistic transport, quantized conductance, quantum Hall effect, with a particular focus on imaging and tuning electron transport in the different regimes. We also collaborate with a spin-off company from UCLouvain, VOCSens, to develop new strategies for gas sensing based on nanomaterials.
Imaging electron transport down to cryogenic temperature
We develop techniques based on scanning gate microscopy (SGM), in home-made setups operating down to 30 mK. In SGM, the tip of an atomic force microscope is used to induce a moving electrostatic perturbation within an electronic device, and one simultaneously maps the changes in device conductance. From SGM conductance maps, one can infer valuable information on charge transport at the local scale, or in other words, understand "how electrons behave down there". Interpretation of the SGM conductance maps often relies on comparison with simulations results often provided by the group of Jean-Christophe Charlier (IMCN/MODL)
Two-dimensional crystals: synthesis, van der Waals heterostructures, twistronics
For device fabrication, we either rely on different international collaborators, or fabricate devices ourselves in WINFAB, the 1000 m² UCLouvain-based platform dedicated to micro and nanofabrication. Fabrication techniques range from graphene and 2D crystal synthesis/exfoliation and stacking (dry or wet transfer), to nanometer-scale patterning using electron-beam lithography, and electrical contact definition. Particular emphasis is given to twisted heterostructures of different 2D crystals, where moiré superperiods yield correlated electron transport signatures at low temperature.
Gas sensing based on nanomaterials
Nanomaterials and 2D crystals offer new opportunities in the field of gas sensing : they are mainly constituted by surfaces, which constitute the active part of the device in such sensors. The strategy that we develop mainly focuses chemiresistors. We aim at understanding transport phenomena down to the local (nanometer) scale in such devices, and identify the relevant parameters influencing the sensors' sensitivity and reproducibility. This work is performed in collaboration with VOCSens, a UCLouvain spin-off company, as well as with the group of Sophie Hermans (IMCN/MOST) for chemical functionalization of the nanomaterials.