Focussed Helium Ion Beam Exposure of Polymethylmethacrylate: Positive or Negative Tone Images, Polyenes, and Fluorescent Carbon Layers

Understanding chemical transformations in polymethylmethacrylate (PMMA) during helium ion beam exposure will help researchers involved in nanofabrication, materials synthesis or transformation, patterning polyenes, developing phantoms for radiation therapy, and realizing carbonaceous quantum emitters. The level of conjugation in PMMA can be controlled using a helium ion beam to realize patterns that are suitable for positive tone lithography, polyenes, dye-like fluorescent materials, and polycyclic aromatic compounds with very similar properties to carbon dots. High-resolution dose studies employing Raman scattering and atomic force microscopy (AFM) reveal the conditions under which these very different conjugated carbonaceous materials form, their spatial distribution, and dissolution characteristics in common solvents.