The existence of an initial amorphous layer and a turbostratic boron nitride transition layer is one of the main hindrance to heteroepitaxial growth of cubic boron nitride on silicon susbtrate. In this paper, we systematically studied the effect of substrate pretreatment on the amorphous layer composition of cBN films prepared by plasma enhanced CVD, and found that the possible causes for the amorphous layer formation are the native silicon oxide, the oxygen remaining in the vacuum chamber, high energy ion bombardment, and the formation of silicon nitride at high substrate temperature. By 1200 K heating of silicon susbtrate in H2 atmosphere and by controlling the deposition temperature at below 900 K, the crystallinity of silicon susbtrate surface could be retained and the amorphous initial layer removed. Moreover, when the substrate bias is near the puttering effect dominated region, only pure turbostratic boron nitride film could be deposited. By reducing the time span of the substrate bias in puttering effect dominated region during the time dependent biasing technique, the turbostratic boron nitrde transition layer could be partitally eliminated. Nucleation of cubic boron nitride directly on silicon substrate was confirmed by high-resolution transmission electron microscopy. Our results may open up a possible route to cubic boron nitrde eptaxial growth on silicon substrate and lead to the potential high-temperature electronic applications of cubic boron nitride thin films.
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