Transmission electron microscopy study of carbon nanophases produced by ion beam implantation

The formation of carbon nanocrystals, produced by ion implantation of carbon ions into fused SiO2 substrates, followed by 1 h thermal annealing at 1000 °C, in an Ar + 5% H atmosphere has been studied. Combined high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) have been employed for structural characterization of carbon nanophases embedded in the quartz substrate. The dependence of grain size and sample morphology of the carbon nanophases on implantation dose was studied. The carbon nanocrystals formed by the implantation for a dose of 1 × 1016 C/cm2 at 320 keV have been identified as a mixture of c-diamond nanophase and a modified diamond nanophase known as n-diamond. For a higher implantation dose, 5 × 1016 C/cm2, besides n-diamond, another solid carbon nanophase was observed, with a structure known as i-carbon. Following the highest implantation dose 1 × 1017 C/cm2 the sample contained the i-carbon nanophase only. A least-square refinement of SAED patterns was employed for the calculation of unit-cell parameters of identified carbon nanophases.