Hybrid graphite-like / polymer-like amorphous carbon materials by plasma synthesis

Full text: The presentation will address the means for controlled growth of polymeric and graphitic nano-inclusions in amorphous carbon (a-C) materials by microwave (MW) and radio frequency (RF) plasma fabrication processes. Polymer-like and graphite-like nano-inclusions are known as undesirable by-products occurring in carbon materials such as CVD diamond, diamond-like carbon and other materials synthesized using hydrocarbon gases as precursors. These are basic π-conjugated polymers (e.g. trans-polyacetylene, polyphenylene and polyphenylene vinylene), graphite nanoparticles and an sp¹ -hybridised nanowire inclusions. These by-products can be produced in abundance under a non-equilibrium plasma conditions and, remarkably, the inclusions award unusual and highly desirable opto-electronic properties to a-C materials. That is, properties of a-C containing polymeric and/or graphitic nanoinclusions could be modified for paramagnetic behaviour and, a-C materials fabricated under the MW excited plasma can, in addition, become absorption-free in visible (red) - near infrared (N-IR) wavelength range (600 - 1200 nm) with their refractive index tailored (e.g. with a maximum value of 1.9 at 400 nm). The a-C materials produced under the RF plasma exhibit non-stoichiometric properties of graphite-like materials with an ultra-low hydrogen content (~15 at.%), high refractive index (~2.4 in red – N-IR) and unpaired electron concentration (~1021 cm^-3) and a narrow band gap (0.4 – 0.6 eV) mimicking the properties of phenyl polymers. These findings suggest that these nano-inclusions in a-C materials could be promising in the development of bulk nanostructured 'all-carbon' opto-electronic systems. (author)