Surface-enhanced Raman spectroscopy for characterization of nanodiamond seeded substrates and ultrananocrystalline diamond at the early-stage of plasma CVD growth process

Nanodiamond seeds on substrates and ultrananocrystalline diamond (UNCD) at the early-stage of CVD have been characterized by surface-enhanced Raman spectroscopy (SERS). Anodic aluminum oxide (AAO) films encapsulated with two-dimensional arrays of silver nanoparticles are used as the substrates. UNCD is grown by 400 W, 2.45 GHz microwave plasma CVD using detonation nanodiamond as seeds in a gas mixture of 1% methane diluted by 99% argon at the substrate temperature of 400°C and gas pressure of 100 Torr for 15-45 min. Light illumination on Ag nanoparticles induces strong plasmonic coupled local electromagnetic fields for enhancing Raman scattering signals from nanodiamond seeds and UNCD films on AAO substrates at the early-stage of CVD. With electrodeposited silver nanoparticles photoluminescence signal is suppressed for revealing weak Raman signals. Fabrication of the Ag/AAO SERS substrates and the SERS spectra for nanodiamond seeded AAO substrates and ultra-thin UNCD at the early-stage of CVD growth are discussed.