UC Berkeley - Materials Science and Engineering
We are an interdisciplinary team using advanced electron and ion beam microscopes to both characterize and manipulate matter down to the atomic scale. Our work advances fundamental materials understanding and drives the development of prototype devices for the technologies of the future.
Introducing a new method to fabricate triangular nanopores in monolayer hBN
Taking a fresh approach to defect engineering in 2D hexagonal boron nitride (hBN), we first use a dose-controlled helium ion shower to create single-atom vacancies. These ‘seeds’ are then expanded into larger triangular nanopores by the preferential removal of boron atoms, either under electron irradiation in the transmission electron microscope (TEM), or by a thermal treatment in air. This strategy uniquely combines enhanced throughput with atomic-level control.
D.O. Byrne, F.I. Allen, Atomic Engineering of Triangular Nanopores in Monolayer hBN for Membrane Applications: A Decoupled Seeding and Growth Approach, ACS Applied Nano Materials 8(9):4565 (2025) doi:10.1021/acsanm.4c06998
Tuning nanopore edge termination
While nanopores in hBN are often nitrogen-terminated, we have discovered that boron-terminated pores can be created in the scanning transmission electron microscope (STEM) by rastering a 60 keV electron probe over the sample at low dose.
D.O. Byrne, S.M. Ribet, D. Kepaptsoglou, Q.M. Ramasse, C. Ophus, F.I. Allen, Fabrication and characterization of boron-terminated tetravacancies in monolayer hBN using STEM, EELS and electron ptychography, Ultramicroscopy 282:114305 (2026) doi:10.1016/j.ultramic.2025.114305
Delving deeper with electron energy-loss spectroscopy (EELS)
To probe atomic structure and chemistry in ultrathin samples even when regions are obscured by ubiquitous hydrocarbon contamination, we developed a spatially averaged TEM-EELS approach. Here, defect peaks (labeled 1–3) in the boron K-edge indicate varying degrees of B–Ox bonding in ion-irradiated hBN monolayer.
D.O. Byrne, J. Ciston, F.I. Allen, Probing defectivity beneath the hydrocarbon blanket with TEM-EELS, Microscopy and Microanalysis 30(4):650 (2024) doi:10.1093/mam/ozae064
Coming soon…
Exploring new directions in 3D nanoprinting using advanced FIB microscopes
Here we use a state-of-the-art He/Ne focused ion beam (FIB) microscope to create 3D nanostructures with unmatched precision. We demonstrate multimaterial architectures and leverage ion implantation to engineer internal voids.
F.I. Allen, New Directions in Focused Ion Beam Induced Deposition for the Nanoprinting of Functional 3D Heterostructures, Advanced Materials Technologies 11(11):e02542 (2026) doi:10.1002/admt.202502542