Structural units of the grain boundaries in ultrananocrystalline diamond thin films with different grain sizes were investigated using Raman spectroscopy. Characteristic peaks of well-defined molecular structural building blocks were detected in the near-infrared excited Raman spectra of these materials by limiting the excitation volume to the size of the crystallites using an optical microscope and surface enhanced Raman spectroscopy. The analysis of the spectra provided evidence for the presence of aromatic hydrocarbons and different sp3 CHx groups in grain boundaries of these materials.

Grain Boundary Fine Structure of Ultrananocrystalline Diamond Thin Films Measured by Raman Scattering. M.Veres, S.Tóth, M.Koós: Applied Physics Letters, 2007, 91[3], 031913