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    Tunneling current modulation in atomically precise graphene nanoribbon heterojunctions
    (London : Nature Publishing Group, 2021) Senkovskiy, B.; Nenashev, A.; Alavi, S.; Falke, Y.; Hell, M.; Bampoulis, P.; Rybkovskiy, D.; Usachov, D.; Fedorov, A.; Chernov, A.; Gebhard, F.; Meerholz, K.; Hertel, D.; Arita, M.; Okuda, T.; Miyamoto, K.; Shimada, K.; Fischer, F.; Michely, T.; Baranovskii, S.; Lindfors, K.; Szkopek, T.; Grüneis, A.
    Lateral heterojunctions of atomically precise graphene nanoribbons (GNRs) hold promise for applications in nanotechnology, yet their charge transport and most of the spectroscopic properties have not been investigated. Here, we synthesize a monolayer of multiple aligned heterojunctions consisting of quasi-metallic and wide-bandgap GNRs, and report characterization by scanning tunneling microscopy, angle-resolved photoemission, Raman spectroscopy, and charge transport. Comprehensive transport measurements as a function of bias and gate voltages, channel length, and temperature reveal that charge transport is dictated by tunneling through the potential barriers formed by wide-bandgap GNR segments. The current-voltage characteristics are in agreement with calculations of tunneling conductance through asymmetric barriers. We fabricate a GNR heterojunctions based sensor and demonstrate greatly improved sensitivity to adsorbates compared to graphene based sensors. This is achieved via modulation of the GNR heterojunction tunneling barriers by adsorbates.
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    Coupling a single solid-state quantum emitter to an array of resonant plasmonic antennas
    (London : Nature Publishing Group, 2018) Pfeiffer, M.; Atkinson, P.; Rastelli, A.; Schmidt, O.G.; Giessen, H.; Lippitz, M.; Lindfors, K.
    Plasmon resonant arrays or meta-surfaces shape both the incoming optical field and the local density of states for emission processes. They provide large regions of enhanced emission from emitters and greater design flexibility than single nanoantennas. This makes them of great interest for engineering optical absorption and emission. Here we study the coupling of a single quantum emitter, a self-assembled semiconductor quantum dot, to a plasmonic meta-surface. We investigate the influence of the spectral properties of the nanoantennas and the position of the emitter in the unit cell of the structure. We observe a resonant enhancement due to emitter-array coupling in the far-field regime and find a clear difference from the interaction of an emitter with a single antenna.