Polarization-Driven Asymmetric Electronic Response of Monolayer Graphene to Polymer Zwitterions Probed from Both Sides
Polarization-Driven Asymmetric Electronic Response of Monolayer Graphene to Polymer Zwitterions Probed from Both Sides
复制标题
单层石墨烯对聚合物两性离子的偏振驱动不对称电子响应从两侧探测
DOI：
10.1021/acsami.1c13505
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发表时间：
2021
影响因子：
9.5
通讯作者：
Barnes, Michael D.
中科院分区：
文献类型：
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作者：
Hight-Huf, Nicholas;Nagar, Yehiel;Levi, Adi;Pagaduan, James Nicolas;Datar, Avdhoot;Katsumata, Reika;Emrick, Todd;Ramasubramaniam, Ashwin;Naveh, Doron;Barnes, Michael D.
我们研究了两性离子聚合物的石墨烯表面掺杂的性质，以及使用新的样品几何形状的弱面内和强面间屏蔽的影响，该几何形状允许直接进入石墨烯/聚合物界面的石墨烯或聚合物侧。同时使用开尔文探针和静电力显微镜，我们观察到一个显着的上移费米能级在石墨烯的260毫电子伏，主要是由极化率的变化，而不是纯粹的电荷转移与有机覆盖层。这一物理图像得到了密度泛函理论（DFT）计算的支持，该计算描述了石墨烯中电荷的重新分布，以响应吸附的两性离子部分的偶极子，类似于局部DC斯塔克效应。通过采用倒置的几何形状观察到吸附的偶极子的强金属样屏蔽，DFT确定的效果产生于限制在靠近两性电偶极子的石墨烯侧的电荷的强烈不对称再分布。传输测量证实了n型掺杂对载流子迁移率没有显著影响，从而证明了在将联合收割机石墨烯与光刻图案化聚合物组合的器件中获得期望的电子性质的途径。
We investigated the nature of graphene surface doping by zwitterionic polymers and the implications of weak in-plane and strong through-plane screening using a novel sample geometry that allows direct access to either the graphene or the polymer side of a graphene/polymer interface. Using both Kelvin probe and electrostatic force microscopies, we observed a significant upshift in the Fermi level in graphene of ∼260 meV that was dominated by a change in polarizability rather than pure charge transfer with the organic overlayer. This physical picture is supported by density functional theory (DFT) calculations, which describe a redistribution of charge in graphene in response to the dipoles of the adsorbed zwitterionic moieties, analogous to a local DC Stark effect. Strong metallic-like screening of the adsorbed dipoles was observed by employing an inverted geometry, an effect identified by DFT to arise from a strongly asymmetric redistribution of charge confined to the side of graphene proximal to the zwitterion dipoles. Transport measurements confirm n-type doping with no significant impact on carrier mobility, thus demonstrating a route to desirable electronic properties in devices that combine graphene with lithographically patterned polymers.