Growing graphene on polycrystalline copper foils by ultra-high vacuum chemical vapor deposition

We show that monolayer graphene can be grown isothermally on polycrystalline copper foils via ultra-high vacuum chemical vapor deposition (UHV-CVD), using acetylene as a carbon precursor. The growth is self-limiting, yielding monolayer graphene with a quality comparable to that of graphene grown by atmospheric- or low-pressure chemical vapor deposition. Copper sublimation, a typical concern for UHV-CVD, is shown to be suppressed by growing graphene domains. Further, the roughness of the copper surface after growth is similar to that of copper foils after growth processes at higher pressures. A dependency of the growth kinetics on the surface orientation of the copper grains is observed and a growth model including all stages of growth is presented and discussed. Similar to observations at higher growth pressures, the graphene domains possess sigmoidal growth, however the overall growth behavior is more complicated with two subsequent growth modes. The role of hydrogen is investigated and shows that, contrary to reports for higher growth pressures, dissolved hydrogen in the copper foil plays an essential role for graphene growth whereas ambient hydrogen does not have a noticeable influence.