The effect of self-assembled monolayers on graphene conductivity and morphology

Graphene transport properties are limited by charge defects in SiO$_{2}$, and by large charge density due to strong interaction with SiC. To modify these effects we have treated 300 nm SiO$_{2}$ with tricholosilanes with different termination groups including pure and fluoro and amino-terminated hydrocarbons for use as substrates for mechanical exfoliation of graphene. XPS measurements verify the presence of the expected termination groups. AFM measurements reveal modified monolayer roughness and correlation lengths; for a fluorinated carbon chain the RMS roughness is 0.266 $\pm $ 0.017 nm and the correlation length is 10.2 $\pm $ 0.7 nm compared to 0.187 $\pm $ 0.011 nm and 19.8 $\pm $ 2.5 nm for SiO$_{2}$. Surface free energies of the monolayers and the SiO$_{2}$ blank have been computed from static contact angle measurements and all decrease the SiO$_{2 }$surface free energy; for the fluorinated carbon chain monolayer a decrease of 20 mJ/m$^{2}$ from SiO$_{2}$. We will discuss the ease of exfoliation, and the morphology and conductivity of graphene on these monolayers.