| AVS 66th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology Division | Thursday Sessions |
| Session NS+2D+QS-ThM |
| Session: | Direct Atomic Fabrication by Electron and Particle Beams & Flash Session |
| Presenter: | Marek Kolmer, Oak Ridge National Laboratory |
| Authors: | M. Kolmer, Oak Ridge National Laboratory W. Ko, Oak Ridge National Laboratory A.-P. Li, Oak Ridge National Laboratory |
| Correspondent: | Click to Email |
Techniques based on multiprobe scanning tunneling microscopy (MP-STM) allow determination of charge and spin transport in variety of systems supported on surfaces of solid materials. In classical 2- and 4-probe methods STM tips are navigated by scanning electron microscope or high-resolution optical microscope typically in micrometer scales down to hundreds of nanometers. These MP-STM methods are currently regarded as universal tools for in-situ characterization of mesoscopic transport phenomena [1,2].
Such a mesoscopic experimental paradigm has recently been changed by downscaling of 2-probe STM experiments towards the atomic level [3,4]. In this case current source and drain probes are positioned in atomically defined locations with respect to the characterized nanosystems. Our experiments rely on fully STM-based tip positioning protocol with probe-to-probe separation distances reaching tens of nm [3,4]. Such probe-to-probe lateral positioning precision is combined with about pm vertical sensitivity in probe-to-system contacts. These two factors enable realization of two-probe scanning tunneling spectroscopy (2P-STS) experiments, where transport properties can be characterized by macroscopic probes kept in atomically defined tunneling conditions [4].
Here, we will apply 2P-STS methodology to probe quantum transport properties in functional systems: graphene nanoribbons (GNRs) epitaxially grown on the sidewalls of silicon carbide (SiC) mesa structures. These GNRs display ballistic transport channels with exceptionally long mean free paths and spin-polarized transport properties as proven by mesoscopic multiprobe transport experiments [5-7]. Interestingly, the nature of these ballistic channels remains an open question. We will show that 2P-STS experiments give new insight into quantum origin of the transport behaviors.
[1] Li, A.-P. et al., Adv. Funct. Mater., 23 (20), 2509-2524 (2013)
[2] Voigtländer B. et al., Rev. Sci. Instrum., 89(10), 101101 (2018)
[3] Kolmer M. et al., J. Phys.: Condens. Matter, 29(44), 444004 (2017)
[4] Kolmer M. et al., Nat.Commun., 10, 1573 (2019)
[5] Baringhaus J., Nature, 506, 349–354 (2014)
[6] Aprojanz J. et al., Nat.Commun., 9, 4426 (2018)
[7] Miettinen A.L. et al., submitted, arXiv:1903.05185 (2019)
This work was conducted at the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility.