Ion beam synthesis of WC-SiC nanocomposite thin layers and their electron field emission properties

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A WC-SiC nanocomposite thin layer structure consisting of nano-grains of WC embedded in SiC has been fabricated on an n-type Si substrate by ion beam synthesis (IBS) using a metal vapor vacuum arc ion source. A SiC layer was first formed by high dose carbon implantation into the silicon substrate. Subsequent W implantation was preformed to form the WC-SiC nanocomposite structure that can be achieved under appropriate implantation and annealing conditions. Characterization of the implanted samples was performed using atomic force microscopy (AFM), conducting AFM, x-ray photoelectron spectroscopy, and transmission electron microscopy. Excellent field emission properties with an ultra-low turn-on field of 0.35 V/μm from such a nanocomposites structure have been achieved. While it has been demonstrated that the surface morphology effect and the local electrical inhomogeneity are two field enhancement mechanisms for IBS SiC/Si structures, they are not sufficient to account for the excellent emission properties of these WC-SiC nanocomposite layers. To explain the excellent field emission properties from these structures, a proximity field enhancement effect between closely spaced conducting grains in a dielectric medium and an internal quantum tunneling mechanism are proposed.