The growth of diamond crystals by chemical vapor deposition (CVD) has been intensively pursued for more than two decades.  Only in the past few years has homoepitaxial growth (diamond on diamond) proven possible for the preparation of thin films.  However, the use of diamond substrates renders this method impractical for large scale applications.

We have developed a chemical vapor deposition (CVD) process to grow large (3 mm diameter) single crystals of diamond on thin epitaxial metal films. Iridium (melting point 2450 oC) is a good lattice match to diamond and is highly resistant to carbide formation.

We first grow epitaxial (001) Ir films (typically 300 nm thick) on terraced SrTiO3, LaAlO3, or Al2O3 substrates by electron beam evaporation at high deposition temperatures. Diamond nucleation on Ir is initiated by low-energy positive ion bombardment in a methane/hydrogen microwave plasma-enhanced CVD chamber.  Following this key step, dense diamond nuclei cover the entire substrate.

After a few minutes of growth, the crystallites are sufficiently dense and well oriented that their [110] lateral facets coalesce, creating a single crystal diamond film.  Detailed x-ray analysis, electron back-scattering diffraction, and Raman scattering confirm a single crystal diamond structure and sp3 bonding.  The diamond plates can be detached from the substrate.  They are transparent at a thickness of 35 µm.

research: diamond

Phone:517-355-9708

Fax: 517-432-5501

Email: golding@pa.msu.edu

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Growth of diamond crystals by

heteroepitaxy

Single crystal of diamond grown by CVD heteroepitaxy.  The sample measures 1.3 mm by 0.4 mm and is 0.04 mm thick.  The top surface is a (001) crystallographic face; the lateral surfaces are formed by cleaving and lie along two orthogonal (110) directions.  The cleavage faces are (111) surfaces, just as for natural diamond.

Epitaxial film of iridium grown by electron beam evaporation on strontium titanate. This is a map of the Ir surface topography made by an atomic force scanning microscope.  The film shows atomic height terraces on the (100) surface.  The vertical scale, or roughness, is only 20 nm.  Diamond is grown on this iridium surface, for which the lattice parameter mismatch is 7.5%.

To learn more…

Epitaxial Iridium Growth on Strontium Titanate, Z. Dai, A. Li, C. Bednarski, L.I. McCann, and B. Golding, Proc. Mat. Res. Soc 684, P11.35. (2001).

Support…

Thanks to the NSF Center for Sensor Materials

Connie Bednarski, Zhongning Dai, and An-Ping Li