Microstructural characterization of diamond films deposited on c-BN crystals

The morphology and structure of diamond films, deposited on cubic boron nit ride (c-BN) crystals by microwave-plasma-enhanced chemical vapor deposition , is studied by high-resolution scanning electron microscopy and micro-Rama n spectroscopy. The c-BN crystals, with sizes of 200 to 350 mu m and grown by a high-temperature/high-pressure technique, were embedded in a copper ho lder, and used as substrates in deposition runs of 15 min to 5 h. The nucle ation centers for diamond appear as well-shaped cuboctahedral crystallites, having diameters of approximately 100 nm. With increasing deposition time the diamond crystallites grew larger, forming islands on the c-BN faces. In some cases, epitaxial growth was observed on the (111) c-BN faces where co alesced particles gave rise to very smooth regions. A number of diamond cry stals with peculiar shapes are observed, such as a pseudo five-fold symmetr y due to multiple twinning. Moreover, both randomly distributed carbon tube s, about 100 nn in diameter and 1 mu m in length, and spherically shaped fe atures are observed in samples prepared under the typical conditions of dia mond deposition, this effect being ascribed to the influence of plasma-sput tered copper contamination. Quite unusual diamond crystals with a deep, pyr amidal-shaped hole in the middle grew on the copper substrate between the c -BN crystals. (C) 2000 Elsevier Science S.A. All rights reserved.