The effect of a SiC cap on the growth of epitaxial graphene on SiC in ultra high vacuum

Thin and homogeneous graphenes with excellent thickness uniformity were produced on the carbon-rich surface of a SiC crystal using an ultra high vacuum technique. The sample surface was capped by another SiC substrate with a silicon-rich face to form a shallow cavity between them. During the graphene growth by high temperature annealing, silicon atoms sublimated from the capped sample were trapped inside the cavity between the two substrates. The confined vapor phase silicon maintains a relatively high partial pressure at the sample surface which significantly reduces the extremely high growth rate of epitaxial graphene to an easily controllable range. The structure and morphology of the graphene samples grown with this capping method are characterized by low energy electron diffraction and Raman spectroscopy and the results are compared with those of layers grown on an uncapped sample surface. The results show that capping yields much thinner graphene with excellent uniformity.