A method was proposed and examined to deposit thick cubic boron nitride (cBN) -rich layer of good adhesion to silicon substrate. The method combined (i) the insertion of a thick sp(2) buffer layer, and (ii) the use of an appropriate assist ion beam energy for the growth of the cBN-rich top layer. The sp(2)-bonded boron nitride buffer layer was deposited under irradiation of ions with energies in the range of 200-360 eV The buffer layer was found to contain curled graphitic basal planes, and so was supposed to be relatively deformable, and facilitate the relaxation of stresses in the cBN-rich top layer. The ion assist introduced during the growth of the cBN-rich layer was supposed to both create and annihilate defects, and so resulted in the generation and relaxation of internal stresses. Results showed that the insertion of a 492 nm sp2 buffer layer, and the use of a beam energy of 450 eV for assisting the growth of the top layer can produce a 643-nm-thick cBN-rich top layer with satisfactory adhesion, a high cBN content of 87 vol %, a hardness of 57 GPa, and an elastic modulus of 612 GPa. (C) 2004 American Vacuum Society.