Formation of Q‐Carbon Nanoballs and Nanodiamonds by Pulsed Laser Annealing of Patterned Polymer Structures

Abstract 2D and 3D patterned structures of Q‐carbon nanoballs and nanodiamonds have been created by laser writing of polymers, carbonization, and pulsed laser annealing. Specifically, 2D and 3D patterns of polymeric structures have been prepared by using a direct‐laser‐writing (DLW) process involving two‐photon polymerization (2PP). These patterned structures are carbonized to create amorphous carbon structures in various 2D and 3D forms. The sp 3 /sp 2 ratio (%) of these carbonized structures ranged from 45–55%, as determined by Raman and XPS studies. These carbonized structures are turned into Q‐carbon nanoballs or nanodiamonds by controlling the undercooling during nanosecond laser melting and quenching. The laser‐annealed structures varied from crystalline graphite (onion‐like structures) to diamond to Q‐carbon with increasing undercooling. The size range (average) of nanoballs is determined to be ≈45–50 nm, and it is ≈3–5 nm for nanodiamonds. The laser‐annealed structures are characterized by Raman and XPS for their bonding characteristics and HRTEM/STEM (HAADF) for detailed structural characterization. The Raman spectrum from nanodiamonds exhibited a downshift to 1327 cm −1 as a result of phonon confinement. The Raman spectra from Q‐carbon nanoballs confirmed the characteristic double hump centered ≈1340 and 1500 cm −1 peaks.