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 sp(2)/sp(3) ratio in the unannealed sample and the sample annealed at 900 degrees C and 1500 degrees 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 degrees C are similar to those of the unannealed sample. However, the spectra of the sample annealed at 1500 degrees C are very different. Annealing at 900 degrees 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 degrees C. Copyright (C) 2010 John Wiley & Sons, Ltd.