Electrical Engineering and Computer Sciences, University of California , Berkeley, California 94720, United States.
J Am Chem Soc. 2014 Jun 4;136(22):7853-6. doi: 10.1021/ja5033327. Epub 2014 May 20.
Air-stable doping of transition metal dichalcogenides is of fundamental importance to enable a wide range of optoelectronic and electronic devices while exploring their basic material properties. Here we demonstrate the use of benzyl viologen (BV), which has one of the highest reduction potentials of all electron-donor organic compounds, as a surface charge transfer donor for MoS2 flakes. The n-doped samples exhibit excellent stability in both ambient air and vacuum. Notably, we obtained a high electron sheet density of ~1.2 × 10(13) cm(-2), which corresponds to the degenerate doping limit for MoS2. The BV dopant molecules can be reversibly removed by immersion in toluene, providing the ability to control the carrier sheet density as well as selective removal of surface dopants on demand. By BV doping of MoS2 at the metal junctions, the contact resistances are shown to be reduced by a factor of >3. As a proof of concept, top-gated field-effect transistors were fabricated with BV-doped n(+) source/drain contacts self-aligned with respect to the top gate. The device architecture, resembling that of the conventional Si transistors, exhibited excellent switching characteristics with a subthreshold swing of ~77 mV/decade.
过渡金属二硫属化物的空气稳定掺杂对于实现各种光电和电子器件至关重要，同时也能探索其基本材料特性。在这里，我们展示了使用具有所有电子供体有机化合物中最高还原电位之一的苄基紫精 (BV) 作为 MoS2 薄片的表面电荷转移供体。n 型掺杂样品在空气和真空中均表现出优异的稳定性。值得注意的是，我们获得了约 1.2×10(13) cm(-2)的高电子面密度，这对应于 MoS2 的简并掺杂极限。BV 掺杂剂分子可以通过浸入甲苯中可逆地去除，从而提供了控制载流体面密度以及按需选择性去除表面掺杂剂的能力。通过在金属结处对 MoS2 进行 BV 掺杂，接触电阻降低了>3 倍。作为概念验证，采用与顶栅自对准的 BV 掺杂 n(+)源/漏接触制造了顶栅场效应晶体管。该器件结构类似于传统的 Si 晶体管，具有约 77 mV/decade 的亚阈值摆幅，表现出优异的开关特性。
