Multilayer nanocrystalline/microcrystalline diamond films studied by laserreflectance interferometry

Laser reflectance interferometry (LRI) was used as an in situ diagnostic to ol to monitor the growth rate and surface roughness far a diamond film grow n using a three-step chemical vapor deposition (CVD) process in which a mul tilayer (nanocrystalline/microcrystalline/nanocrystalline) structure was pr oduced. This multilayer structure was achieved by regulating the concentrat ion of N-2 in a H-2/CH4 microwave plasma. The observed LRI interference fri nges clearly show a decrease in surface roughness (i.e. an increase in refl ectivity) for the nanocrystalline layer grown over the rough microcrystalli ne layer, Raman spectra of single and multilayer diamond films are compared . We find that high phase purity microcrystalline diamond can nucleate on a smooth nanocrystalline diamond layer and that, in turn, a smooth nanocryst alline layer can nucleate on the relatively rough microcrystalline laver. T his results in a composite-like film whose toughness, hardness, and surface roughness properties can be tailored as desired. (C) 2000 Elsevier Science S.A. All rights reserved.