Diaphite: diamond-graphene hybrid nanostructures grown in CH4/H2/N2 chemistry 

Abstract

Here, we demonstrate the deposition of Diaphitic domains (diamond-graphene composite nanostructure) in a hydrogen (H2)-rich plasma gas chemistry. The distinct structural characteristics formed within ultra-nanocrystalline diamond (UNCD) films, with varying nitrogen (N2) concentrations in the gas mixture from 5% to 20%, were examined using a combination of electron microscopy and diffraction methods. Atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements indicated the formation of an average diamond grain size of ∼ 5 nm. High-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) revealed the presence of five-fold, six-fold and twelve-fold symmetry features, along with a forbidden {200} crystallographic reflection associated with the Diaphite structure in the UNCD films. These hybrid features, which combine elements of both diamond and graphene, were observed in both 5% and 10% N2-doped UNCD films and are the result of the interface between sp3 and sp2 domains, where sp3 grains are covalently bonded with sp2 grains.The emergence of these unconventional features in artificially grown diamonds is linked to nitrogen doping and secondary nucleation initiated by H2, leading to non-equilibrium growth conditions that potentially induce polymorphism in the diamond.Our discoveries offer insights into the creation of structural defects that are correlated with N2 doping in a plasma mixture of CH4/H2, thus enabling the development of novel nanodiamond structures through regulated doping.