Synthesis mechanism and 'orthodoxy' test based field emission analysis of hybrid and pristine graphene nanowalls deposited on thin Kovar wires

Graphene nanowalls (GNWs) also known as carbon nanowalls (CNWs) and GNWs-carbon nanofibers (CNFs) hybrid nanostrucrures are grown on metallic wires using a two-step microwave plasma enhanced chemical vapour deposition (MW-PECVD) process. Here, plasma is generated in two steps (first at lower pressure and then at higher operating pressure) to avoid arcing on the metallic wire during the growth. Combination of Raman and transmission electron microscopy studies revealed presence of herringbone CNFs in the hybrid nanostructures that are grown with -100 V bias compared to pristine GNWs that are grown without any bias. A new approach for field emission (FE) analysis is created by combining FN equation with 'orthodoxy test' in a modified approach to avoid spurious results. Here, hybrid nanostructures exhibited higher current and more repeatable field emission characteristics over 4 cycles of operation. Post FE investigations indicate that while pristine GNWs underwent many deformities and structural changes, hybrid structures remain almost unscathed. These investigations point out that a novel synthesis mechanism can be used to grow GNW based hybrid nanostructures for different applications like X-ray sources which involves FE at the core.