Growth of c-diamond, n-diamond and i-carbon nanophases in carbon-ion-implanted fused quartz

Abstract

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 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, a crystalline CO _x phase 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 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 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 ions cm⁻², have a Fm3m modified 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 the cubic P2₁3 (or P4₂32) structure known as i-carbon. These buried layered diamond-related materials may have applications for field emission devices.