Peculiarities of the Impact of a Helium Ion Beam on an Intercalated Graphite Film

Intercalated graphite is a promising carbon material for use as field-emission media, since carbon nanostructures can be synthesized in them using simple experiments. However, there is insufficient data in publications on the influence of ion exposure on the physical properties of intercalated graphite. The work studies the surface morphology and structure of composite films based on intercalated graphite obtained by processing graphite powder and Fe, Ni, Y₂O₃, and Cr impurities in an oxidizing solution of nitric and sulfuric acids. The changes in the films that occur under the influence of helium-ion bombardment are shown. It is established that the obtained films contain two modifications of graphite with different interplanar distances: hexagonal P 63mc (0.247 nm) and metastable rhombohedral R-3m (0.246 nm). It is demonstrated that the X-ray photoelectron spectra of the C 1s level correspond to crystalline carbon with different degrees of hydrogenation of the chemical structure. It is revealed that the films are characterized by the absence of an ordered surface-relief structure and consist of randomly oriented aggregates of particles. The formation of graphite flakes of various shapes and thicknesses of approximately several tens of nanometers is detected. A slight change in the surface morphology of the samples activated by helium plasma is noted. It is determined that graphite-like sp² clusters are more resistant to ion irradiation than sp³ clusters. It is shown that during the process of bombardment of the film with helium ions, the rearrangement of sp³ clusters into more stable chemical structures C–O, C–O–C and C=O occurs. The average size of the sp² clusters is ~5 nm.