We are an interdisciplinary team using advanced electron and ion beam microscopes to image and manipulate matter down to the atomic scale, embracing advanced spectroscopic techniques to delve deeper into the chemical and electronic properties of our materials.
Electron microscopes are traditionally employed for imaging, whereas ion microscopes are generally used for material shaping by sputtering. We turn the tables on these conventions, since there are unique benefits to be gained from interchanging (and combining) these approaches. For example, we use state-of-the-art transmission electron microscopy (TEM) to both image materials at atomic resolution and also to delicately arrange atoms into particular configurations. Analogously, we explore the use of focused ion beam (FIB) microscopes to image materials in new ways, as well as to modify materials due to ion irradiation effects.
We are committed to applying the techniques we develop to advance fundamental understanding of material properties and to build prototype devices for emerging applications.
High-resolution TEM image showing triangular nanopores in monolayer hexagonal boron nitride fabricated using a combined ion and electron irradiation technique.
Image credit: Dana Byrne, UC Berkeley.
Byrne DO, Ciston J, Allen FI. Probing Defectivity Beneath the Hydrocarbon Blanket in 2D hBN Using TEM-EELS. Microscopy and Microanalysis. 2024: ozae064. doi:10.1093/mam/ozae064
(Left) Helium ion micrograph of butterfly wing scale with gallium-ion-milled cross-section to investigate thickness of lamina.
(Right) Higher magnification view showing lamina (L), ridges (R), and crossribs (r). The thickness of the lamina determines the color of the butterfly wing scale (structural color effect).
Image credits: Rachel Thayer and Frances Allen (UC Berkeley).
Thayer RC, Allen FI, Patel NH. Structural color in Junonia butterflies evolves by tuning scale lamina thickness. Elife. 2020;9. doi:10.7554/eLife.52187
(Top) Nanopillar with tip radius <10nm fabricated by focused helium ion beam-induced deposition from a tungsten precursor onto a specialized AFM microcantiveler.
(Bottom) Single frame from a movie of DNA in liquid scanned using such a custom AFM tip.
Image credits: Frances Allen and Bibiana Onoa (UC Berkeley).
Allen FI, De Teresa JM, Onoa B. Focused Helium Ion and Electron Beam-Induced Deposition of Organometallic Tips for Dynamic Atomic Force Microscopy of Biomolecules in Liquid. ACS Appl Mater Interfaces. 2024;16: 4439–4448. doi:10.1021/acsami.3c16407
