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Directed Control of Carrier Type and Density in Ferroelecric-gated Graphene through Interface Engineering 
May 13, 2013   11:00am - 11:30am
  Video Only

Graphene/ferroelectric hybrid structures – while showing exciting performance in terms of high mobility and the accessibility of distinguishable, nonvolatile resistance states – have not yet shown their full potential: the direct control of the carrier density and type in graphene through variation of the ferroelectric polarization. This control could provide new means of manipulating electron transport in graphene through complex ferroelectric gate structures. However, hysteresis effects observed in previous studies of graphene on ferroelectric oxide thin films have been attributed to effects other than the ferroelectric polarization, presumably the charging of interface states or charge redistribution facilitated through polar molecules at the interface. Here, we present graphene/PbZr0.2Ti0.8O3 (PZT) hybrid structures that exhibit bidirectional interdependency between the graphene doping level and the ferroelectric polarization. This work was enabled by the development of a one-touch transfer process that allows for direct transfer of high-quality CVD grown graphene onto the ferroelectric film surface to ensure beneficial interfacial properties. Furthermore, complete current-voltage and ferroelectric studies of graphene-contacted ferroelectric capacitors including evidence of reversible ferroelectric polarization switching of epitaxial PZT thin films are demonstrated. Additionally, detailed current-voltage studies of ferroelectric-gated graphene transistors reveal that the manipulation of the polarization state of the ferroelectric gate oxide impacts both the carrier type and the density of carriers in the graphene if environmental factors that impact the process are controlled. Detailed pulse-width- and time-dependent measurements have been used to separate the role of ferroelectric polarization effects from extrinsic charging or charge redistribution effects at the interface. This work is key to understanding prior studies and routes to utilization of ferroelectric-gated graphene for potential devices. Two-dimensional Raman and photocurrent mapping of graphene transferred to pre-defined polydomain structures demonstrate the ability to utilize ferroelectric gate oxides for the creation of graphene devices with selectable potential steps down to the nanoscale.

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