Sun Hantao, Jiang Zhuoling, Xin Na, Guo Xuefeng, Hou Shimin, Liao Jianhui
Centre for Nanoscale Science and Technology, Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing, 100871, China.
Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
Chemphyschem. 2018 Sep 5;19(17):2258-2265. doi: 10.1002/cphc.201800220. Epub 2018 Jun 20.
We present a robust approach to fabricate stable single-molecule junctions at room temperature using single-layer graphene as nanoelectrodes. Molecular scale nano-gaps in graphene were generated using an optimized fast-speed feedback-controlled electroburning process. This process shortened the time for creating a single nano-gap to be less than one minute while keeping a yield higher than 97 %. To precisely control the gap position and minimize the effects of edge defects and the quantum confinement, extra-narrow grooves were pre-patterned in the graphene structures with oxygen plasma etching. Molecular junctions were formed by bridging the nano-gaps with amino-functionalized hexaphenyl molecules by taking advantage of chemical reactions between the amino groups at the two ends of the molecules and the carboxyl groups at the edges of graphene electrodes. Electronic transport measurements and transition voltage spectroscopy analysis verified the formation of single-molecule devices. First-principles quantum transport calculations show that the highest occupied molecular orbital of hexaphenyl is closer to the Fermi level of the graphene electrodes and thus the devices exhibit a hole-type transport characteristics. Some of these molecular devices remained stable up to four weeks, highlighting the potential of graphene nano-electrodes in the fabrication of stable single-molecule devices at room temperature.
我们展示了一种稳健的方法，即使用单层石墨烯作为纳米电极在室温下制造稳定的单分子结。通过优化的快速反馈控制电烧蚀工艺在石墨烯中产生分子尺度的纳米间隙。该工艺将创建单个纳米间隙的时间缩短至不到一分钟，同时保持产率高于97%。为了精确控制间隙位置并最小化边缘缺陷和量子限制的影响，利用氧等离子体蚀刻在石墨烯结构中预先图案化了超窄沟槽。通过利用分子两端的氨基与石墨烯电极边缘的羧基之间的化学反应，用氨基功能化的六苯基分子桥接纳米间隙来形成分子结。电子输运测量和跃迁电压光谱分析证实了单分子器件的形成。第一性原理量子输运计算表明，六苯基的最高占据分子轨道更接近石墨烯电极的费米能级，因此这些器件表现出空穴型输运特性。其中一些分子器件在长达四周的时间内保持稳定，突出了石墨烯纳米电极在室温下制造稳定单分子器件方面的潜力。
