Probing charge transport in nanocontacts on low-dimensional materials
Dr. Pantelis Bampoulis (PIN)
Abstract: The importance of metal contacts in nanodevices cannot be overstated; in essence, the ‘contact’ defines the device’s characteristics. Efficient charge injection from metal nanocontacts to low-dimensional quantum materials is crucial in realizing high-performance nanodevices. Despite its high importance, the ‘contact’ on quantum materials remains a largely unexplored topic. This is because of the lack of experimental methods for non-invasively probing the interface, and the sensitivity of these low-dimensional materials to external perturbations, such as those induced by metal contacts. On top of that, a continuous decrease in the size of electronics, Moore’s law, constitutes the need for characterization methods capable of accurately and locally examining interfaces. Scanning probe microscopies with their high accuracy and low noise levels can help tackle these challenges. Using scanning probe techniques such as conductive atomic force microscopy and four-point probe scanning tunneling microscopy, we were able to contact low-dimensional materials with metal nanoelectrodes and investigate charge transport with atomic precision. In this approach, a conductive tip acts as the metal electrode in contact with the material of interest. This allows for simultaneous recording of topography images along with current-voltage curves in different experimental settings and with various contact characteristics. As a first example, I will elaborate on the influence of surface quality in the charge transport characteristics in metal nanocontacts on two-dimensional semiconductors such as MoS2 and WS2. The second topic of this talk focuses on graphene nanoribbons on SiC, where we demonstrate a precise control of transport through contacting multiple, independent, ballistic tracks. Lastly, I will expand the discussion on one-dimensional ballistic transport to germanene nanoribbons through the realization of edge states.