Tuning the transport properties of graphene films grown by CVD on SiC(0001): Effect ofin situhydrogenation and annealing

The structural, optical, and transport properties of graphene grown by chemical vapor deposition (CVD) of propane under hydrogen on the Si face of SiC substrates have been investigated. We show that little changes in temperature during the growth can trigger the passivation of the SiC surface by hydrogen. Depending on the growth condition, hole or electron doping can be achieved, down to a few ${10}^{11}$ cm${}^{\ensuremath{-}2}$. When the growth temperature is high ($T\ensuremath{\approx}1500--1550{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}$C), we obtain electron-doped graphene monolayers lying on a buffer layer. When the growth temperature is slightly lowered ($T\ensuremath{\approx}1450--1500{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}$C), hole-doped graphene layers are obtained, lying on a hydrogen-passivated SiC surface, as confirmed by the enhancement of the mobility (of the order of 4500 cm${}^{2}/$Vs) and the persistence of weak localization almost up to room temperature (250 K). The high homogeneity of this graphene allows the observation of the half-integer quantum Hall effect, typical of graphene, at the centimeter scale in the best cases. The influence of the SiC steps on the transport properties is discussed.