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 400W, 2.45GHz 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 100Torr for 15–45min. 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.