page_title: Boron nitride nanosheet
section_title: Mechanical cleavage
hierarchical_section_title: Boron nitride nanosheet / Synthesis / Mechanical cleavage
caption_attribution_description: TEM image of few-layer BN, with the selected-area electron diffraction pattern (inset) indicating a layered BN structure. Scale bar, 50 nm.
context_page_description: Boron nitride nanosheet is a two-dimensional crystalline form of the hexagonal boron nitride, which has a thickness of one to few atomic layers. It is similar in geometry to its all-carbon analog graphene, but has very different chemical and electronic properties – contrary to the black and highly conducting graphene, BN nanosheets are electrical insulators with a band gap of ~5.9 eV, and therefore appear white in color.
  Uniform monoatomic BN nanosheets can be deposited by catalytic decomposition of borazine at a temperature ~1100 °C in a chemical vapor deposition setup, over substrate areas up to about 10 cm². Owing to their hexagonal atomic structure, small lattice mismatch with graphene, and high uniformity they are used as substrates for graphene-based devices.
context_section_description: Mechanical cleaving methods of boron nitride use shear forces to break the weak van der Waals interactions between the BN layers. Cleaved nanosheets have low defect densities and retain the lateral size of the original substrate. Inspired by its use in the isolation of graphene, micromechanical cleavage, also known as the Scotch-tape method, has been used to consistently isolate few-layer and monolayer boron nitride nanosheets by subsequent exfoliation of the starting material with adhesive tape. The disadvantage of this technique is that it is not scalable for large-scale production.
  Boron nitride sheets can be also exfoliated by ball milling, where shear forces are applied on the face of bulk boron nitride by rolling balls. This technique yields large quantities of low-quality material with poor control over its properties.
caption: A typical electron micrograph of BN nanosheets prepared by ball milling (scale bar 50 nm).[8]
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