Field emission studies of carbon nanostructures synthesised over Ni–Cr catalyst layer

Current research on the carbon-based nanotechnology needs progressive methods to control the shape, location and size of the nanostructures. Here, we report significant progress by synthesising the density controlled carbon nanostructures (CNSs) using acetylene and hydrogen in microwave plasma enhanced chemical vapour deposition system. Thin films of Ni–Cr (80 : 20, 60 : 40 and 50 : 50) sputtered over silicon (1 0 0) were used as catalysts. Scanning electron microscopy images of plasma annealed Ni–Cr coated silicon substrates show distributed nanoparticles of varying compositions over plasma annealed substrates. Morphologically and structurally different CNS were obtained when plasma annealed substrates were exposed to carbon vapours present in plasma. Transmission electron microscopy images suggested that the length and tip of CNS were in the range 50–100 nm and 4–6 nm, respectively. High resolution transmission electron microscopy images of the samples confirmed the presence of graphite (0 0 2) and nickel (2 0 0) planes in CNS. The field emission studies and Kelvin probe measurements of CNS grown over 80 : 20 Ni–Cr substrate show turn-on field and corresponding work function as 1.4 V µm−1 and 4.4 eV, respectively. Preliminary results show that these nanostructures could act as stable field emitters.