Improved electron field emission from metal grafted graphene composites

Metal nanoparticle grafted graphene films (GFs) form a new composite for electron field emission devices. The GFs were deposited on Ni coated Si wafers by microwave plasma enhanced chemical vapour deposition. Graphene-based composites using Ti, Pd, Ag and Au were formed by thermal evaporation. The surface morphology and microstructure were probed by scanning and high resolution transmission electron microscopy. Improvement in the electron field emission and reduction in the turn on and threshold fields were observed in metal grafted GFs as compared to those from pristine films. It was found that among the grafted metals, Ti adsorption contributed more efficiently in enhancing the electron field emission properties by lowering its work function. The enhanced electron field emission characteristics were analyzed using the density functional theory calculations for metal grafted graphene ribbon. Our results indicate increased density of states near the Fermi level for metal grafted graphene ribbon which is responsible for the improvement in electron field emission. We suggest that grafting of metal nanoparticles on GFs could be exploited for the development of efficient field emitters.