Tunneling Spectroscopy of Two-Dimensional Materials Based on Via Contacts

Abstract

We introduce a novel planar tunneling architecture for van der Waals heterostructures based on via contacts, namely metallic contacts embedded into through-holes in hexagonal boron nitride ($h$BN). We use the via-based tunneling method to study the single-particle density of states of two different two-dimensional (2D) materials, NbSe${}_2$ and graphene. In NbSe${}_2$ devices, we characterize the barrier strength and interface disorder for barrier thicknesses of 0, 1 and 2 layers of $h$BN and study the dependence on tunnel-contact area down to $(44\pm 14{)}^2$ nm${}^2$. For 0-layer $h$BN devices, we demonstrate a crossover from diffusive to point contacts in the small-contact-area limit. In graphene, we show that reducing the tunnel barrier thickness and area can suppress effects due to phonon-assisted tunneling and defects in the $h$BN barrier. This via-based architecture overcomes limitations of other planar tunneling designs and produces high-quality, ultra-clean tunneling structures from a variety of 2D materials.

References in corpus (7)

• Atomically thin boron nitride: a tunnelling barrier for graphene devices
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• The phonon dispersion of graphite by inelastic x-ray scattering
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Cited by in corpus (3)

• Andreev reflection spectroscopy in strongly paired superconductors
• Tomasch Oscillations as Above-Gap Signature of Topological Superconductivity
• Building 3D superconductor-based Josephson junctions using a via transfer approach