Surface characterization on graphitization of nanodiamond powder annealed in nitrogen ambient

A nanodiamond thin film is deposited on a single crystal silicon substrate by dip-coating technique. Surface characterization of the unannealed nanodiamond sample, and the samples annealed at various temperatures in nitrogen ambient, is conducted by XPS and Raman spectroscopy. The fitting data of the C1s core level XPS peak reveal that the sp2/sp3 ratio in the unannealed sample and the sample annealed at 900 °C and 1500 °C are 0.44, 0.55 and 6.08 respectively. All spectra including the C1s core level XPS spectrum, the plasmon energy-loss spectrum associated with C1s peak, C KVV Auger spectrum of the sample annealed at 900 °C are similar to those of the unannealed sample. However, the spectra of the sample annealed at 1500 °C are very different. Annealing at 900 °C fails to produce appreciable graphitization, and an onion-like carbon structure with a small diamond core is formed when the nanodiamond is heated to 1500 °C. Copyright © 2010 John Wiley & Sons, Ltd.