Si and N - Vacancy color centers in discrete diamond nanoparticles: Raman and fluorescence spectroscopic studies

摘要

The present study reports on an innovative method to prepare discrete diamond nanoparticles or nanodiamonds (NDs) with high structural and optical quality through top-down approach by controlled oxidation of pre-synthesized nanocrystalline diamond (NCD) film. These NDs are studied for their structural and optical properties using atomic force microscopy (AFM), Raman and fluorescence (FL) spectroscopy. While AFM analysis confirms uniform distribution of discrete NDs with different sizes varying from a few tens of nanometers to about a micron, spectroscopic investigations reveal the presence of impurity - vacancy related color centers exhibiting FL at 637 and 738 mu as a function of particle size. In addition, an intense emission originating from vacancy centers associated with N and Si (SiV-) is observed for all NDs at the temperature close to liquid nitrogen. A detailed spectral analysis is carried out on the structural defects in these NDs. The full width at half maximum of diamond Raman band (similar to 1332 cm(-1)) is found to be as narrow as 1.5 cm(-1) which reveals the superior structural quality of these NDs. Further, mapping of diamond Raman and FL spectra of SiV- confirm the uniform distribution of NDs throughout the substrate. The narrow line widths and a minimal shift in peak positions of Raman and FL spectra endorse this aspect.