Diamond nucleation on surfaces using carbon clusters
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Thin solid films of C6o and C70 have been used as nucleating layers for the growth of diamond thin films on a variety of substrate surfaces, including metal, insulator, and semiconductors. Compared to other forms of carbon, such as graphite, amorphous carbon, soot, etc., it is found that the nucleation density on a C70 film is equivalent to that of diamond seeds themselves. On the other hand, diamond nucleation on a C6o film is less favorable. We argue from our experiments that the reason for C70 film to have such favorable nucleating properties is its chemical stability and geometry. A working model is proposed to explain the nucleation of diamond on solid C70 films. Application of this work extending to the growth of diamond on a wide range of substrates is also discussed.
I. INTRODUCTION The success in growing thin diamond films using chemical vapor deposition methods has stimulated interest in the unique properties of diamond for potentially new technological applications. As an example, diamond has the combined properties of good electrical insulation, high thermal conductivity, and low dielectric constant which make it well suited for use in device packaging and multichip module technologies. The extreme hardness and wide optical bandgap of diamond would also provide an excellent protective coating material for a variety of optical applications. The chemical inertness and hardness of diamond thin films would also find wide utilization as a protective coating against corrosion and wear in the cutting tool and metal working industries. A number of different deposition techniques have been developed to deposit diamond thin films.1"5 A fundamental problem encountered in most deposition methods is the limited understanding and controllability of diamond nucleation on non-diamond substrates. At present, the most common method to obtain substantial nucleation of diamond on non-diamond substrates is a pretreatment step. This pretreatment is regularly accomplished by simply polishing the sample with diamond grit or paste before placing it in the deposition chamber. Without some type of diamond seeding, not enough diamond crystallites nucleate on the surface of most materials in a reasonable amount of time to eventually grow and coalesce into continuous films. This pretreatment, however, is not easily adapted toward coating large or nonplanar surface areas.
^Present address: Grumman Corp., A01-26, Corp. Research Center, Bethpage, New York 11714-3580. J. Mater. Res., Vol. 9, No. 1, Jan 1994
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In this paper we provide a more comprehensive discussion on a nucleation method described in an earlier publication.6 This technique eliminates the need for surface abrasion and diamond seeding by using thin layers of fullerene films sublimated onto various non-diamond substrates. The thin fullerene layer produces a large number of nucleation sites suitable for the formation of continuous diamond films. The specificity of the type of fullerene is found to aid in elucidating t
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