High-k dielectric oxides are supposedly ideal gate-materials for ultra-high doping in graphene and other 2D-crystals. Here, we report a temperature-dependent electronic transport study on chemical vapor deposited-graphene gated with SrTiO3 (STO) thin film substrate. At carrier densities away from charge neutrality point the temperature-dependent resistivity of our graphene samples on both STO and SiO2/Si substrates show metallic behavior with contributions from Coulomb scattering and flexural phonons attributable to the presence of characteristic quasi-periodic nano-ripple arrays. Significantly, for graphene samples on STO substrates we observe an anomalous 'slope-break' in the temperature-dependent resistivity for T550 to 100 K accompanied by a decrease in mobility above 30 K. Furthermore, we observe an unusual decrease in the gate-induced doping-rate at low temperatures, despite an increase in dielectric constant of the substrate. We believe that a complex mechanism is at play as a consequence of the structural phase transition of the underlying substrate showing an anomalous transport behavior in graphene on STO. The anomalies are discussed in the context of Coulomb as well as phonon scattering.
Bibliographical noteFunding Information:
We would like to acknowledge for financial support from NRF-CRP ‘‘Tailoring Oxide Electronics by Atomic Control’’ Grant No. NRF2008NRFCRP002-024, CRP Award No. NRF-CRP9-2011-3, NUS cross-faculty grant, FRC, BMBF, the Singapore National Research Foundation [grants NRF-RF2008-07, NRF-CRP(R-144-000-295-281), SMF-NUS Research Horizon (Phase II), NUS-Young Investor Award (R144-000-283-101), IMRE/10-1C0109, and NUS/SMF], U.S. Office of Naval Research (ONR and ONR Global), and the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Global Research Lab. 20110021972, 2011K000615, 20110017587, 20110006268, and Global Frontier Research Program 20110031629).
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