Nucleation and growth of diamond on carbon-implanted single crystal copper surfaces
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The nucleation and growth of diamond crystals on single crystal copper surfaces has been studied. Microwave plasma enhanced chemical vapor deposition (MPECVD) was used for diamond nucleation and growth. Prior to diamond nucleation, the single crystal copper surface is modified by carbon ion implantation at an elevated temperature (~820 °C). This procedure leads to the formation of a graphite film on the copper surface, resulting in an enhancement of diamond crystallite nucleation. A simple lattice model has been constructed to describe the mechanism of diamond nucleation on graphite as (lll)diamond parallel to (0001)graphite and (110)diamond parallel to (1120)graphite- This leads to a good understanding of diamond growth on carbon-implanted copper surfaces.
I. INTRODUCTION The unique properties of diamond make it one of the most desirable materials for high power electronic devices.1 However, the technology of high quality single crystal diamond film growth thus far is limited to homoepitaxy.2 One reason for this limitation is that diamond nucleation on non-diamond substrates is very difficult due to the extremely high surface energy of diamond.3 An attempt to grow epitaxial diamond film on a single crystal Ni substrate has met little success.4 The explanation is that nickel preferentially turns the carbon gas species into soot or graphitic carbon.5-6 Koizumi et al.1 reported that diamond can be grown heteroepitaxially on a single crystal c - B N substrate (lattice constant a = 3.616 A vs adiamond = 3.5671 A). However, a large single crystal of c - B N is even harder to come by than diamond itself. The largest c - B N crystal that can be synthesized so far is only 100 /mm. Copper (a = 3.6148 A) is the next best candidate for the substrate, due to its small lattice mismatch with diamond and low carbon solubility precluding the possibility of carbide formation. Like most other materials, the surface energy of copper is very small, compared with that of diamond (ycu(ioo) = 2.08 J/m 2 ; ydiamond(ioo) ~ 9.2 J/m 2 ). 3 ' 8 A very interesting initial study of using the copper crystals as substrates for diamond growth is to modify the surface energy of the copper to enhance diamond nucleation. This increase in surface energy is accomplished by a)
Present address: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, M/S 303-308, Pasadena, California 91109-8099. J. Mater. Res., Vol. 7, No. 9, Sep 1992
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carbon ion implantation prior to diamond growth. In this paper, the study of the nucleation and growth of diamond on modified surfaces of single crystal Cu(100) and C u ( l l l ) is presented, and a model to explain diamond growth on ion-implanted copper surface is proposed. II. EXPERIMENTAL Copper shot (99.999% pure) was utilized to produce the single crystal copper boule using the Bridgman technique. Sample pieces in a size of about 10 X 10 X 1 mm 3 were sliced from the boule along (100) or (111) crystal orientations. Carbon ion implant
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