Metal ion mixing in diamond

We have carried out some investigations of the mixing of thin metal films into diamond by energetic metal ion bombardment. Free-standing diamond films were made by microwave plasma-assisted CVD, onto which films of Nb or Ta, approximately 100-Å thick, were deposited using a filtered vacuum arc plasma technique. The metalized diamond was then bombarded with a Ta and Nb ion-beam, respectively, at an energy of 150 keV and to an applied dose of ∼7×1016 ions/cm2. The Nb and Ta depth profiles were measured by 2 MeV He+ Rutherford backscattering spectrometry. Intense intermixing was produced between the original metal overlay, the diamond matrix, and the implanted atoms; and the concentration depth profiles were found to be well-described by the predictions of the TRIM code. Here, we outline the techniques used for diamond synthesis and the preparation of free-standing films, the vacuum arc plasma deposition of Nb and Ta thin films, and the Ta and Nb ion implantations; and we describe our observations of the ion-mixed films formed in this way.