AFM Characterization of Hexagonal Boron Nitride Dielectrics

Van der Waals heterostructures often rely on electrostatic gating to tune the carrier density in the two-dimensional material of interest. In many cases, large gate voltages are necessary to significantly shift the Fermi level or to apply large displacement fields, which requires ultra-high quality gate dielectrics. In this presentation, we report on using a conductive Atomic Force Microscope (AFM) tip to characterize defects in hexagonal boron nitride (hBN), the primary gate dielectric in van der Waals heterostructures. We initially characterize the hBN flakes by measuring the voltage that must be applied to the AFM tip to break down the hBN dielectric at the point below the tip. Following this procedure, we test whether the breakdown voltage can be improved by electrostatically moving defects using voltage applied to the AFM tip. We present the results of our characterization and defect manipulation to improve hBN dielectric breakdown.