Low-field electron emission properties from intrinsic and S-incorporated nanocrystalline carbon thin films grown by hot-filament CVD

Results are reported on the electron field emission properties of intrinsic and S-incorporated nanocrystalline carbon (n-C:S) thin films grown on molybdenum substrates by hot-filament CVD technique from methane-hydrogen (CH₄/H₂) and hydrogen sulphide-hydrogen (H₂S/H₂) gas pre mixtures respectively. The field emission properties for the S-incorporated films were investigated as a function of substrate temperature (T_s). Lowest turn-on field was observed at 4.5 V/μm for one of the sample, which was grown at 900 °C, demonstrating the effect of sulfur addition. The S-incorporation also causes microstructural and structural changes, as characterized with ex situ techniques such as SEM, AFM and Raman spectroscopy (RS). S-assisted films show smoother surfaces and finer-grained than those grown without it. The electron field emission properties of S-assisted films is also compared to the film grown without it (intrinsic) at a particular deposition temperature and the turn-on field was found to be almost half for the S-assisted film than for the non S-assisted film. The influence of growth temperature was also conducted and an inverse correlation was found with the turn-on field (E_c). These studies were performed in order attempt to "tailor-the-material" as a viable cold cathode material by introducing the defects and altering the electronic structure.