Figure 3.

Metastable quantized growth of triangular nanopores. (a) For each quantized triangular pore size, an image shows the atomic configuration of the pore and the resultant pore area. Nitrogen and boron atoms are depicted in blue and gold respectively. The spacing between neighboring boron and nitrogen atoms, a_o, is 1.45 Å. (b–i) A time series showing the quantized growth of a triangular nanopore in h-BN from a few-atom vacancy to approximately 8 nm² under a beam current of 6 A/cm². (b) mono to few-atom vacancy formed in bottom h-BN sheet, circled in yellow. (c–i) Metastable quantized growth of nanopore. Shuttering the electron beam irradiation causes the pore growth to cease. Images are taken at roughly 2 minute intervals. (j) A plot of pore area versus dose for the images shown in (a–h). The inset shows a similar growth of pore area versus dose for the nanopore shown in Fig. 2(f) and a neighboring vacancy of similar size in the second layer under a beam current of 3 A/cm². Unlike the pore that spans the full thickness of the h-BN, the vacancy that sits on top of another layer of h-BN does not grow at an appreciable rate.