Field electron emission from diamond-like carbon films deposited using RF inductively coupled CH4-plasma source

Diamond-like carbon (DLC) films 4-400 nm thick were deposited on conductive n-Si and metal substrates using direct ion beam deposition from an RF inductively coupled CH4-plasma (ICP) source. The held electron emission of the films was examined as a function of deposition conditions and post-deposition surface modification by Ni ultrathin coatings. Electrical properties of the films were studied as well. A specially designed high vacuum scanning tunnelling-field emission microscope was employed for simultaneous mapping of the topography, work function and local held electron emission intensity. Stable, low voltage emission was observed after the emission electric field/current activation process. The activation mechanism was probably the formation of conductive channels in the films to supply electrons for emission from low work function surface areas. Deposition of ultrathin metal coatings on the DLC films reduced both the effective barrier height and the held emission threshold. The DLC films surface coated with ultrathin Ni films resulted in electron emission at fields as low as 20-25 V mu m(-1). It was shown that DLC films with thicknesses in the range 5-15 nm demonstrated efficient field emission long-term stability. The results are interpreted based on the reduced electrical resistivity of nanometer scale thick films, and deviation of resistivity over the surface. (C) 1998 Published by Elsevier Science S.A.