Rizzo Daniel J, Wu Meng, Tsai Hsin-Zon, Marangoni Tomas, Durr Rebecca A, Omrani Arash A, Liou Franklin, Bronner Christopher, Joshi Trinity, Nguyen Giang D, Rodgers Griffin F, Choi Won-Woo, Jørgensen Jakob H, Fischer Felix R, Louie Steven G, Crommie Michael F
Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.
Kavli Energy NanoSciences Institute , University of California Berkeley , Berkeley , California 94720 , United States.
Nano Lett. 2019 May 8;19(5):3221-3228. doi: 10.1021/acs.nanolett.9b00758. Epub 2019 Apr 24.
The ability to tune the band-edge energies of bottom-up graphene nanoribbons (GNRs) via edge dopants creates new opportunities for designing tailor-made GNR heterojunctions and related nanoscale electronic devices. Here we report the local electronic characterization of type II GNR heterojunctions composed of two different nitrogen edge-doping configurations (carbazole and phenanthridine) that separately exhibit electron-donating and electron-withdrawing behavior. Atomically resolved structural characterization of phenanthridine/carbazole GNR heterojunctions was performed using bond-resolved scanning tunneling microscopy and noncontact atomic force microscopy. Scanning tunneling spectroscopy and first-principles calculations reveal that carbazole and phenanthridine dopant configurations induce opposite upward and downward orbital energy shifts owing to their different electron affinities. The magnitude of the energy offsets observed in carbazole/phenanthridine heterojunctions is dependent on the length of the GNR segments comprising each heterojunction with longer segments leading to larger heterojunction energy offsets. Using a new on-site energy analysis based on Wannier functions, we find that the origin of this behavior is a charge transfer process that reshapes the electrostatic potential profile over a long distance within the GNR heterojunction.
通过边缘掺杂剂调节自下而上生长的石墨烯纳米带（GNRs）的带边能量的能力，为设计定制的GNR异质结及相关纳米级电子器件创造了新机遇。在此，我们报道了由两种不同氮边缘掺杂构型（咔唑和菲啶）组成的II型GNR异质结的局域电子特性，这两种构型分别表现出供电子和吸电子行为。使用键分辨扫描隧道显微镜和非接触原子力显微镜对菲啶/咔唑GNR异质结进行了原子分辨结构表征。扫描隧道谱和第一性原理计算表明，由于咔唑和菲啶掺杂构型具有不同的电子亲和力，它们会引起相反的向上和向下轨道能量偏移。在咔唑/菲啶异质结中观察到的能量偏移量取决于构成每个异质结的GNR段的长度，段越长，异质结能量偏移越大。通过基于Wannier函数的新的在位能量分析，我们发现这种行为的起源是一个电荷转移过程，该过程在GNR异质结内的长距离上重塑了静电势分布。
