Tunneling Spectroscopy of Two-Dimensional Materials Based on Via Contacts
arXiv:2203.07394 · doi:10.1021/acs.nanolett.2c03081
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 (BN). We use the via-based tunneling method to study the single-particle density of states of two different two-dimensional (2D) materials, NbSe and graphene. In NbSe devices, we characterize the barrier strength and interface disorder for barrier thicknesses of 0, 1 and 2 layers of BN and study the dependence on tunnel-contact area down to nm. For 0-layer 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 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.
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