Nano-crystals of c-diamond, n-diamond and i-carbon grown in carbon-ion implanted fused quartz

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 1017 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 Fdm diamond following a dose of 0.5 1017 C/cm2, whereas clusters of 8-13 nm diameter, for a higher dose of 2 1017 C/cm2, have a Fmm modified phase of diamond known as n-diamond. The largest clusters, diameter 15-40 nm, for a dose of 5 1017 C/cm2, have the cubic P213 (or P4232) structure known as i-carbon. These buried layered diamond and diamond-related materials may have applications for field emission and optical waveguide type devices.