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Characterizing Individual Defects in a Bulk Insulator

(Top) STM topographic image of a clean graphene/BN area (Bottom) dI/dV map acquired simultaneously with topo image exhibits new features including bright dots, a dark dot and a ring.

Scientific Achievement
Demonstrated a new method that can be applied to study individual defects in a widely used bulk insulating material, hexagonal boron nitride (h-BN), by employing scanning tunneling microscopy (STM).

Significance and Impact
Understanding defect behavior is crucial for determining material properties. This provides a new technique for visualizing the electronic properties of individual defects in insulators.

Research Details

  • STM cannot typically be used to study insulators
  • In this experiment h-BN was capped with a single sheet of graphene, which permitted visualization of charge defects in the underlying h-BN crystal. STM extracts details of a defect’s electronic properties by directly detecting how electrons in graphene respond to defect in underlying bulk insulator
  • Discovered that it is possible to manipulate charge states of individual BN defects by applying voltage pulses with STM tip

D Wong, J Velasco Jr, L Ju, J Lee, S Kahn, H-Z Tsai, C Germany, T Taniguchi, K Watanabe, A Zettl, F Wang, M Crommie; Nature Nanotech (2015)