Graphene is one of the strongest and most electrically and thermally conductive materials in nature; therefore, incorporating even traces of graphene into other materials can significantly enhance their mechanical, electrical, and thermal properties. Such graphene-based materials can be used in many applications, including flexible displays, batteries, supercapacitors, solar panels, and mobile devices. However, developing graphene-based 2D materials is challenging. In this study, a facile single-step synthesis method for fabricating thin layers of amorphous carbon (a-C) containing planar graphene (PG) and orbicular graphitic carbon (OGC) nanostructures was developed by thermal annealing in inert atmosphere using an sp3-rich a-C thin film as a precursor. By annealing thin-film stacks of Si/NiFe/a-C, a thin layer with a hybrid a-C-PG-OGC structure was produced with OGC nanostructures forming on top of PG nanostructures and pyramidal NiSix nanocrystals extending into the Si substrate due to the diffusion of nickel during elevated-temperature annealing. Raman spectroscopy and cross-sectional transmission electron microscopy confirmed the transformation from amorphous to graphitic structure in the a-C film during thermal annealing. The obtained results demonstrate that the development of this 2D material with a hybrid a-C-PG-OGC microstructure is due to a metal-catalyzed PG nucleation mechanism and a mismatch-induced OGC growth mechanism. The present method for synthesizing graphene-containing thin-film structures paves the way toward the fabrication of complex micro-assemblies where high strength and good thermoelectric properties are of paramount importance.

The relatively high toughness, high adhesion to steel, and low internal stress of hydrogenated amorphous carbon (a-C:H) films containing Ag make them good candidate materials for various applications in sensors, tribology, and biomaterials; however, the relatively low hardness and poor tribological properties in oxidizing environments hinder their broad use. Incorporating a small amount of Si in Ag/a-C:H films may modify the film microstructure and, in turn, improve their mechanical and tribological properties. To test this hypothesis, Ag/Si/a-C:H films were synthesized by magnetron sputtering and their microstructure, composition, and mechanical/tribological properties were examined with various microanalysis techniques and mechanical testing methods. The Si content of the films was varied by controlling the rotational speed of the substrate. It is shown that the incorporation of Si in the films increases the sp 3 C, sp 3 CH, and sp 3 CH2 contents, slightly roughens the film surface, and greatly improves the mechanical and tribological properties through the formation of a SiC phase. The results of this study also show that there is a critical Si content for optimal tribological properties.