AVS 63rd International Symposium & Exhibition
    2D Materials Focus Topic Thursday Sessions
       Session 2D+MI-ThM

Paper 2D+MI-ThM5
Electronic Transport and Localization in Nitrogen-Doped Graphene Devices Using Hyperthermal Ion Implantation

Thursday, November 10, 2016, 9:20 am, Room 103B

Session: Properties of 2D Materials including Electronic, Magnetic, Optical, Mechanical, Thermal Properties
Presenter: Adam Friedman, Naval Research Laboratory
Authors: A.L. Friedman, Naval Research Laboratory
C.D. Cress, Naval Research Laboratory
S.W. Schmucker, National Research Council postdoc working at Naval Research Laboratory
J.T. Robinson, Naval Research Laboratory
O.M.J. van 't Erve, Naval Research Laboratory
Correspondent: Click to Email
Chemical alteration of graphene facilitates doping and may add a usable transport gap. For most published studies, atomic species (e.g., fluorine or hydrogen) are chemically bonded to the surface out-of-plane, breaking the sp2 symmetry and replacing it with an sp3 bond. These methods produce functionalized graphene, rather than substitutionally-doped graphene, where the former is typically only chemically stable for days (e.g., fluorine) or weeks (e.g., hydrogen) or less, depending on environmental conditions. Hyperthermal ion implantation offers a controllable method of producing high-quality substitutionally doped graphene with nitrogen, an n-type dopant that has great potential for graphene electronics and spintronics applications where high carrier concentration, uniform doping, and minimal vacancy defect concentration is desired [1]. Here we examine the transport properties of monolayer graphene sheets as a function of implantation beam energy and dose. We observe a transition from weak (metal) to strong (insulator) localization that varies as a function of carrier concentration, and we find that the transition is suppressed near the Dirac point for higher amounts of nitrogen [2]. For nominally equivalent doses, increased N ion energy results magnetoresistance magnitude increases, reaching a value as approximately -5.5% at 5,000 Oe, which we discuss in the context of dopant concentration and defect formation. We use a model for the temperature dependence of the conductivity that takes into account both temperature activation, due to the formation of a transport gap, and Mott variable-range hopping, due to the formation of defects, to further study the electronic properties of the doped films as a function of dose and N ion energy. We find that the temperature activation component dominates the behavior, further indicating that the implanted nitrogen, rather than defects, is responsible the observed result.

[1] C.D. Cress, et al. ACS Nano 10, 3714 (2016).

[2] A.L. Friedman, et al. Phys. Rev. B, 93 161409(R) (2016).