▎ 摘　　要

Direct formation of graphene films on dielectric substrates is investigated by the "etching-precipitation" method which converts metal-carbon mixed films to graphene films by etching metal away by Cl-2 at 600-650 degrees C. Here we report a new approach for improved control of the layer number and continuity of the graphene films. Reactive sputtering of Fe in C2H4/Ar enabled fine control of the carbon concentrations and thicknesses of the initial Fe-C films, which yielded continuous multilayer graphene films of controllable average layer numbers of similar to 10-40, low resistivity down to similar to 240 mu Omega cm, and high Raman G-band to D-band intensity ratio up to 16 directly on SiO2 substrates. We also show that the carbon concentration of the initial Fe-C films determines the film continuity and crystallinity of the graphene.