Surface properties of nanodiamond films deposited by electrophoresis on Si(100)

The surface properties of diamond nanoparticles (40-50 Angstrom in diameter) have been investigated by X-ray photoelectron spectroscopy (XPS), UV photoelectron spectroscopy (UPS) and Raman spectroscopy. The diamond nanoparticles have been deposited on flat Si(100) substrates by electrophoresis/dielectrophoresis. The as-deposited films are strongly oxidized and present a 1-2% nitrogen content. After treatment at 850 degrees C in H-2 plasma for 60 min, the oxygen is removed, and the position of the C 1s core-level peak indicates a n-type electronic comportment of the diamond nanoparticles. Raman spectroscopy of the as-deposited film shows a sp(3) contribution at 1321 cm(-1) and a sp(2) contribution around 1620 cm(-1). The 12 cm(-1) shift of the sp(3) contribution with respect to the bulk diamond peak at 1333 cm(-1) is attributed to a phonon confinement effect due to the size of the diamond particles. The H-2 plasma treatment induces a size decrease of the nanocrystallites confirmed by Raman and scanning electron microscopy (SEM) measurements. UPS spectroscopy shows a negative electron affinity of -0.2 eV of the hydrogenated nanodiamond film. (C) 1999 Elsevier Science S.A. All rights reserved.