Tip-enhanced Raman spectroscopy studies of nanodiamonds and carbon onions

Nanodiamond powder was annealed at temperatures ranging between 700 and 1700 °C and deposited by electrophoretic deposition on steel substrates. Far-field Raman spectroscopy and tip-enhanced Raman spectroscopy were used to investigate structural changes after the transformation from nanodiamonds to carbon onions as a function of the annealing temperature. Enhancement of the Raman signal was observed for all samples irrespective of the hybridization state. The largest enhancement on the order of 105 was found for non-annealed nanodiamonds. Far-field Raman spectroscopy and tip-enhanced Raman spectroscopy showed similar results as a function of the annealing temperature for peak position and width of the D- and G-peaks, intensity ratio ID/IG, and area integrated intensity ratio AD/AG. [Display omitted]