Nanoscale sculpting of hBN with an electron beam and characterization via PL microscopy and ionic transport

Rachael N. Keneipp
University of Pennsylvania, Philadelphia, Pennsylvania, USA _______________________________________

Creating sub- to few-nanometer defects and nanopores in hexagonal boron nitride (hBN) opens opportunities for engineering quantum emitters and for nanofluidic and sensing applications. Using the electron beam in the aberration-corrected scanning transmission electron microscope, we demonstrate modification, thinning, and drilling of features in few-
layer hBN membranes (~ 5-to-20-nm-thick). The atomic composition is monitored with electron energy loss spectroscopy, which also facilitates drift correction. We report effects of electron-beam energy and exposure times on defect size and structure. While previous studies focused on beam energies ? 80 keV to avoid material damage, we show that drilling is
favorable at a higher beam energy of 200 keV. The drilling rate at 200 keV is about 10 times larger than at 80 keV (~ 1.2 vs. 0.1 nm/min), and smaller pores are achievable with minimized damage to the surrounding material. Thinned hBN nanoscale features demonstrate enhanced emission via photoluminescence spectroscopy. For sub-nm hBN pores, ionic transport measurements confirm the complete opening of the 2D hBN pores made through the AC-STEM drilling.

Email: rkeneipp@sas.upenn.edu