Heteroepitaxy of diamond on c-BN: Growth mechanisms and defect characterization
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Long Wang and Pirouz Pirouz Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7217
Walter R. L. Lambrecht Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7217 (Received 13 October 1993; accepted 8 March 1994)
Diamond films grown on {100}, {111} boron-terminated, and nitrogen-terminated facets of cubic boron nitride (c-BN) single crystals were characterized by Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The evolution of morphology and microstructure of the diamond films at different stages during the growth process were followed by SEM investigation. The results indicate that diamond growth proceeds by nucleation of oriented three-dimensional islands followed by their coalescence. Cross-sectional TEM specimens were prepared from thick (over 10 yarn) continuous diamond films grown on {111} boron-terminated surfaces. Selected-area diffraction and high resolution TEM images show that the diamond film has a parallel orientation relationship with respect to the substrate. Characteristic defects, common to diamond films obtained by chemical vapor deposition on other substrates, are also discussed.
I. INTRODUCTION The unique properties of diamond1 make applications in extreme conditions possible where other materials are inadequate.2'3 Some of the interesting applications of diamond are related to its semiconducting properties. In order to use diamond to fabricate high temperature, high power, and fast electronic devices, large area singlecrystal diamond layers are needed.4'5 Since low pressure synthesis of diamond 6 ' 8 using atomic hydrogen to inhibit graphitic deposits and to achieve high growth rates9"12 was demonstrated, different approaches have been used to grow single-crystal diamond films. In one technique, well-faceted octahedral diamond crystallites are seeded in an array of pyramidal pits etched into a (100) oriented silicon wafer.13 Subsequent deposition of diamond on this seeded substrate produces large area films of highly oriented diamond particles; the film contains low-angle grain boundaries with approximately 0.2° tilt angles. Another idea combines homoepitaxial growth on an array of oriented diamond crystals placed together, and subsequent removal of the thin single-crystal diamond film from the surface using ion implantation as a liftoff process.14 In this way, a large diamond template could in theory be fabricated and used to fabricate a new larger diamond template and so on. J. Mater. Res., Vol. 9, No. 7, Jul 1994
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Ideally, the most convenient way is heteroepitaxial growth of diamond on easily available, large singlecrystal substrates. So far, evidence of heteroepitaxial growth of diamond on Si,15"17 Ni,18-19 Cu,20 c-BN,21-26 SiC,27'28 and BeO 29 has been obtained. The best result achieved so far is a highly oriented diamond film, with low-angle grain boundaries, obtained using a SiC buffer layer on a 2 i
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