Nanostructured surfaces

Structural Evolution of Nickel Atoms by Carbon Implantation

O. Morozov, S. Utenkov, V. Seliukova
NSC-Kharkov Institute of Physics and Technology, 61108, Kharkov, Ukraine
E-mail: morozov@kipt.kharkov.ua

Electron-diffraction and electron-microscopic studies have been made into structural transformations in nickel films exposed to different doses of C+ ions.
At first, with increasing concentration of carbon atoms, a diffuse spreading of diffraction rings of the initial face centered cubic (FCC) structure of nickel and the appearance of additional blurred diffuse ring zones are observed. A further increase in the implanted carbon dose is accompanied by reduction in the intensity of the diffraction rings of the FCC structure, and also, by the appearance and growing intensity of the diffraction rings of the HCP structure. On reaching the stoichiometric ratio Ni/C=3/1, the diffractograms exhibit only the rings of the HCP structure with the lattice parameters a=0.266 nm and c=0.433 nm. Note that the diffractograms show the reflections of the metal-nickel sublattice only.
The smoothness of the Ni fcc structure transition to the hcp-phase, as the implanted carbon dose increases, and the completion of the transition only after reaching the stoichiometric ratio Ni/C=3/1 may bear witness to the chemical nature of the observed structural transition with nickel carbide Ni3C formation. However, recognizing that the composite atoms do not form chemical compounds, it may be concluded that the implanted carbon atoms form the hexagonal structure from carbon atoms in the environment of nickel atoms and contribute to the rearrangement of nickel atoms to forming the hcp structure. That is, with an increase in the carbon atom concentration there occurs the graphene plane formation from carbon atoms in the environment of nickel atoms and, simultaneously, nickel atoms rearrange themselves by the law of carbon atoms with the formation of similar hexagonal planes, displayed in the electron-diffraction pattern as the process of hexagonal structure formation with the lattice parameter a=0.266 nm. In other words, the formation of a multilayer system takes place, consisting from successively arranged layers: one from carbon atoms, and the other – from nickel atoms. The presence of significant structure transformations is evidenced by (occurrence of) wide ring diffusion regions observed in the electron-diffraction patterns. 
This suggests an important conclusion that the implantation atoms (carbon atoms in this context) play the predominant role in the formation of the composite structure in the system composed of atoms, which do not form chemical compounds.