Surface and trapped charge characterization of epitaxial oxides for applications in graphene electronics$^{1}$

Trapped charges have been shown to play an important role in the transport properties of graphene supported on SiO$_{2}$, and surface roughness may also play a role. Alternative substrate materials, Sc$_{2}$O$_{3}$ ($\varepsilon \sim $ 14, $n\sim $ 1.9) and Gd$_{2}$O$_{3}$ ($\varepsilon \sim $ 22, $n\sim $ 2) were grown epitaxially by molecular beam epitaxy on Si(111) over a range of thicknesses from 2 nm to 100 nm. AFM measurements yield rms roughness, and correlation function analysis reveals the nature of the long range order. For Sc$_{2}$O$_{3}$, the roughness is strongly thickness dependent, with root-mean-square height 0.26 nm$^{2}$ for a 20 nm thick film and 0.55 nm$^{2}$ for a 65 nm thick film; however, the correlation exponent (2$H\sim $ 1) and correlation length ($\xi \sim $ 20 nm) are the same. The roughness characterization for the full range of thicknesses of both oxides will be presented. In addition, frequency-dependent CV measurements are underway to determine the trapped charge densities. [1] supported by a NRI supplement to the UMD-NSF-MRSEC grant {\#} DMR 0520471.