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Metal nanocluster-based quantum dot sensors for imaging of electrostatic potentials of surfaces and nanostructures
Excellent Research Support Program of UoC (FORUM)

The invention of scanning probe microscopy (SPM) opened the nanoscale world for direct interaction. The following three decades of instrumental and methodological developments turned SPM into a versatile tool for imaging, spectroscopy and manipulation of atomic matter. The recent explosion of interest in quantum-coherent phenomena and their applications to quantum computing creates a unique opportunity for SPM to evolve into a quantum sensing and imaging technique [1]. Our project aims to equip a tuning fork-based non-contact atomic force microscope (NC-AFM) with a metal nanocluster quantum dot (QD) suitable for nanoscale imaging of the electrostatic surface potential. Previously, we demonstrated the principal capabilities of this imaging approach, which we named scanning quantum dot microscopy (SQDM), using a one-molecule QD [2-3]. However, we also found that the fragility of the molecular QD seriously limits the range of SQDM applications. Therefore we intend to use metal clusters as new, robust QD sensors for SQDM. Our planned fabrication procedure begins with the controlled growth of nanometre-sized metal clusters under ultra-high vacuum (UHV) conditions on iridium (Ir[111]) surface covered with a single graphene (Gr) [4] or hexagonal boron nitride (hBN) [5] layer. In the final fabrication step, we will place one or several clusters directly at the apex of the NC-AFM tip by controllably picking them up from the surface.


[1] de Graaf, S. E., Un, S., Shard, A. G., & Lindström, T. (2022). Chemical and structural identification of material defects in superconducting quantum circuits. Materials for Quantum Technology, 2, 032001.

[2] Wagner, C., Green, M. F. B., Leinen, P., Deilmann, T., Krüger, P., Rohlfing, M., Temirov, R., & Tautz, F. S. (2015). Scanning Quantum Dot Microscopy. Physical Review Letters, 115, 026101.

[3] Wagner, C., Green, M. F. B., Maiworm, M., Leinen, P., Esat, T., Ferri, N., Friedrich, N., Findeisen, R., Tkatchenko, A., Temirov, R., & Tautz, F. S. (2019). Quantitative imaging of electric surface potentials with single-atom sensitivity. Nature Materials, 18, 853.

[4] NDiaye, A. T., Bleikamp, S., Feibelman, P. J., & Michely, T. (2006). Two-dimensional Ir cluster lattice on a graphene moiré on Ir(111). Physical Review Letters, 97, 1

[5] Will, M., Atodiresei, N., Caciuc, V., Valerius, P., Herbig, C., & Michely, T. (2018). A Monolayer of Hexagonal Boron Nitride on Ir(111) as a Template for Cluster Superlattices. ACS Nano, 12, 6871.