Cleaning of pyrolytic hexagonal boron nitride surfaces

Hexagonal boron nitride (h-BN) has recently garnered significant interest as a substrate and dielectric for two-dimensional materials and devices based on graphene or transition metal dichalcogenides such as molybdenum disulfide (MoS₂). As substrate surface impurities and defects can negatively impact the structure and properties of two-dimensional materials, h-BN surface preparation and cleaning are a critical consideration. In this regard, we have utilized X-ray photoelectron spectroscopy to investigate the influence of several ex situ wet chemical and in situ thermal desorption cleaning procedures on pyrolytic h-BN surfaces. Of the various wet chemistries investigated, a 10 : 1 buffered HF solution was found to produce surfaces with the lowest amount of oxygen and carbon contamination. Ultraviolet/ozone oxidation was found to be the most effective ex situ treatment for reducing carbon contamination. Annealing at 1050°C in vacuum or 10^-5 Torr NH₃ was found to further reduce oxygen and carbon contamination to the XPS detection limits.