Growth of c-diamond, n-diamond and i-carbon nanophases 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 characterize nanophases of carbon found embedded in fused quartz. These appear after implantation of 1 MeV carbon ions, followed by annealing in argon, oxygenand forming gas for lh 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, acrystalline COxphase is identified at the end of range, following a dose of 5 × 1017 carbon ions cm−2. Three nanocrystalline carbon phases, including diamond, appear after annealing in forming gas; these formalayer 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 diametercrystallize as fcc Fd3m diamond following a dose of 0.5 × 1017 carbon ions cm−2, whereas clusters of 8–13 nm diameter, for a higher dose of 2 × 1017 carbon ionscm−2, have a Fm3mmodified phase of diamond known as n-diamond. The largest clusters (diameter, 15–40nm) for a dose of 5 × 10 17 carbon ions cm−2, have thecubic P213 (or P4232) structure known as i-carbon. These buried layered diamond-related materials may have applications for field emission devices.