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Carbon ions of MeV energy were implanted into sapphire to fluences of 1×1017 or 2×1017 cm-2 and thermally annealed in forming gas (4% H in Ar) for 1 h. Secondary ion mass spectroscopy results obtained from the lower dose implant showed retention of implanted carbon and accumulation of H near the end of range in the C implanted and annealed sample. Three distinct regions were identified by transmission electron microscopy of the implanted region in the higher dose implant. First, in the near surface region, was a low damage region (L1) composed of crystalline sapphire and a high density of plateletlike defects. Underneath this was a thin, highly damaged and amorphized region (L2) near the end of range in which a mixture of i-carbon and nanodiamond phases are present. Finally, there was a pristine, undamaged sapphire region (L3) beyond the end of range. In the annealed sample some evidence of the presence of diamond nanoclusters was found deep within the implanted layer near the projected range of the C ions. These results are compared with our previous work on carbon implanted quartz in which nanodiamond phases were formed only a few tens of nanometers from the surface, a considerable distance from the projected range of the ions, suggesting that significant out diffusion of the implanted carbon had occurred. [ABSTRACT FROM AUTHOR]

Combined high-resolution transmission electron microscopy, selected-area electron diffraction and parallel electron-energy-loss spectroscopy are used to characterize nanophases of carbon found embedded in fused quartz. These appear after implantation of 1 MeV carbon ions, followed by annealing in argon, oxygen and forming gas for 1 h at 1100°C. For argon, virtually all the carbon diffuses out of the substrate with no observable carbon clusters for all doses studied. After annealing in oxygen, a crystalline CO[sub x] phase is identified at the end of range, following a dose of 5 x 10[sup 17] carbon ions cm[sup -2]. Three nanocrystalline carbon phases, including diamond, appear after annealing in forming gas; these form a layer 170 nm beneath the fused quartz surface for all ion doses. The average size of these clusters and the corresponding phases depend on the ion dose; the smallest clusters of 5-7 nm diameter crystallize as fcc Fd3[sup -]m diamond following a dose of 0.5 x 10[sup 17] carbon ions cm[sup -2], whereas clusters of 8-13 nm diameter, for a higher dose of 2 x 10[sup 17] carbon ions cm[sup -2], have a Fm 3[sup -]m modified phase of diamond known as n-diamond. The largest clusters (diameter, 15-40 nm) for a dose of 5 x 10[sup 17] carbon ions cm[sup -2], have the cubic P 2[sub 1]3 (or P4[sub 2]32) structure known as i-carbon. These buried layered diamond-related materials may have applications for field emission devices. [ABSTRACT FROM AUTHOR]

Combined high-resolution transmission electron microscopy, selected area electron diffraction and parallel electron energy loss spectroscopy are used to characterise carbon nano-phases found embedded in fused quartz. These appear after implantation of 1 MeV carbon ions, followed by annealing in argon, oxygen and forming gas for 1 hour at 1100°C. For Ar, virtually all of the carbon diffuses out of the substrate with no observable carbon clusters for all doses studied. After annealing in oxygen, a crystalline COx phase is identified at the end of range, following a dose of 5 × 10[sup 17] C/cm². Three nano-crystalline carbon phases, including diamond, appear after annealing in forming gas: these form a layer 170 nm beneath the fused quartz surface for all ion doses. The average size of these clusters and the corresponding phases depend on the ion dose; the smallest size of 5-7 nm diameter crystallise as fcc Fd&3macr;m diamond following a close of 0.5 × 10[sup 17] C/cm², whereas clusters of 8-13 nm diameter, for a higher close of 2 × 10[sup 17] C/cm², have a Fm&3macr;m modified phase of diamond known as n-diamond. The largest clusters, diameter 15-40 nm, for a close of 5 × 10[sup 17] C/cm², have the cubic P2[sub 1]3 (or P4[sub 2]32) structure known as i-carbon. These buried layered diamond and diamond-related materials may have applications for field emission and optical waveguide type devices. [ABSTRACT FROM AUTHOR]