Charge Carrier Transport in C/SiOC Ceramic Nanocomposites – a Monolith vs. Thin Film Comparative Study
Miniaturization has been considered a major paradigm shift in advanced manufacturing, due to its potential for higher efficiency, faster logistics, and materials reduction. Across many industries including microelectromechanical systems (MEMS) devices, products are getting smaller in size while having more embedded functionalities. One particular interest relates to the use of polymer-derived ceramics (PDC) as high-temperature stable functional materials for applications in e.g. automotive, aerospace, and energy industries. Aside from their high-temperature stability in harsh environments, PDCs possess electrical properties that can be modulated upon adjusting their chemical and phase composition as well as microstructure. The electrical conductivity of monolithic C/SiOC ceramic nanocomposites has been widely studied and exhibits high dependence on the concentration and graphitization state of the segregated sp2 hybridized nanocarbon phase. Depending on the structure and hybridization of the segregated nanocarbon, the electrical conductivity in C/SiOC nanocomposites can vary in a broad range from a strongly insulating (σ < 10-10 (Ω.cm)-1) to a semi-metallic (σ < 102 (Ω.cm)-1) behavior.
The present work assesses the correlation between the amount and order of the free nanocarbon phase in silicon oxycarbides and their charge carrier transport behavior. Thus, the samples were extensively analyzed concerning the thermal evolution of the sp2 carbon phase by means of Raman spectroscopy. Additionally, electrical conductivity and Hall measurements were performed and correlated with the structural information obtained from the Raman spectroscopic investigation. Moreover, a comparative consideration of the charge carrier transport features of monolithic vs. thin-film C/SiOC nanocomposites was performed and will be critically discussed.