Ion irradiation-induced modifications of diamond nanorods synthesised by microwave plasma chemical vapour deposition

Abstract

Diamond nanorods (DNRs) synthesised by the high methane content in argon rich microwave plasma chemical vapour deposition (MPCVD) have been implanted with nitrogen ions. The nanorods were characterised by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The DNRs consist of single-crystalline diamond cores of 3–5 nm in diameter and several tens of nanometres in length. For purification from non-diamond contents, hydrogen plasma etching of DNRs was performed. Structural modifications of etched DNRs were studied after irradiating with 50 keV nitrogen ions under the fluence of 5 × 1014, 1 × 1015, 5 × 1015 and 1 × 1016 ions cm−2. Nitrogen-ion implantation changes the carbon–carbon bonding and structural state of the nanocrystalline diamond (NCD). Raman spectroscopy was used to study the structure before and after ion irradiation, indicating the coexistence of diamond and graphite in the samples. The results indicated the increase in graphitic and sp2-related content, at the expense of decrease in diamond crystallinity, for ion implantation dose of 5 × 1015 cm−2 and higher. The method proves valuable for the formation of hybrid nanostructures with controlled fractions of sp3–sp2 bonding.