Interplay between intercalated oxygen superstructures and monolayerh-BN on Cu(100)

Abstract

The confinement effect of intercalated atoms in van der Waals heterostructures can lead to interesting interactions between the confined atoms or molecules and the overlaying two-dimensional (2D) materials. Here we report the formation of ordered Cu(100) $p(2\ifmmode\times\else\texttimes\fi{}2)$ oxygen superstructures by oxygen intercalation under the monolayer hexagonal boron nitride $(h$-BN) on Cu after annealing. By using scanning tunneling microscopy and x-ray photoelectron spectroscopy, we identify the superstructure and reveal its roles in passivating the exposed Cu surfaces, decoupling $h$-BN and Cu, and disintegrating $h$-BN monolayers. The oxygen superstructure appears as a 2D pattern on the exposed Cu surface or quasi-1D stripes of paired oxygen intercalated in the interface of $h$-BN and Cu predominantly oriented along the moir\'e modulations. The oxygen superstructure is shown to etch the overlaying $h$-BN monolayer in a thermal annealing process. After extended annealing, the $h$-BN monolayer disintegrates into nanoislands with zigzag edges. We discuss the implications of these findings on the stability and oxidation resistance of $h$-BN and relate them to challenges in process integration and 2D heterostructures.