Synthesis of highly oriented CVD diamond films by ultra short bias enhanced nucleation step

Highly oriented diamond films have been deposited on silicon substrate by the MPCVD technique (microwave plasma assisted chemical vapour deposition) using an ultra short bias enhanced nucleation process (so called USBEN). We focus our attention on two points: the homogeneity of the deposit in order to perform a precise characterisation whatever surface location (on 1 X 1 cm(2) of single silicon substrate); and the simplification of the successive steps usually performed in the BEN process. This is carried out by optimising the microwave cavity and the d.c. discharge extension and by keeping the pretreatments just necessary to obtain high nucleation density with an acceptable epitaxial ratio and a good homogeneity. This leads to a drastic reduction of the bias time of only 30 s for low bias voltage. As we obtain a highly oriented diamond film with a short bias pretreatment without preliminary carburation step, we discuss the substrate transformation under a weak bombardment duration of ions having a quite low energy. We think that the bias step probably consists to a slight modification of the substrate surface. (C) 2001 Elsevier Science B.V. All rights reserved.