用氟化双层石墨烯阻挡层实现二维材料的费米能级脱钉
Fermi Level Depinning in Two-Dimensional Materials Using a Fluorinated Bilayer Graphene Barrier
摘要：
强费米能级钉扎（FLP）-通常归因于界面接触处的金属诱导的间隙态-严重降低了结的肖特基势垒高度的可调谐性，并限制了2D材料在电子和光电子学中的应用。在这里，我们表明，氟化双层石墨烯（FBLG）可以用作屏障，以有效地防止FLP在金属/2D材料界面。FLBG可以通过短时间暴露（1-3分钟）于SF6等离子体来产生，SF6等离子体仅氟化具有共价C-F键的双层石墨烯的顶层，而底层保持本征，导致约75 meV的带隙开口。在金属接触和MoS 2层之间插入FBLG显著降低了低功函数金属的肖特基势垒高度（对于Ti和Cr分别为313和260 meV），而对于高功函数金属的肖特基势垒高度增加（对于Pd为160 meV），对应于改进的钉扎因子。我们的研究结果提供了一种直接的方法来产生原子级薄的双金属，不仅可以应用于金属/过渡金属二硫属化物（TMD）界面的费米能级脱钉，而且可以解决电子学和光电子学中的许多其他问题
英文摘要：
Strong Fermi level pinning (FLP) - often attributed to metal-induced gap states at the interfacial contacts - severely reduces the tunability of the Schottky barrier height of the junction and limits applications of the 2D materials in electronics and optoelectronics. Here, we show that fluorinated bilayer graphene (FBLG) can be used as a barrier to effectively prevent FLP at metal/2D materials interfaces. FLBG can be produced via short exposure (1-3 min) to SF6 plasma that fluorinates only the top layer of a bilayer graphene with covalent C-F bonding, while the bottom layer remains intrinsic, resulting in a band gap opening of about 75 meV. Inserting FBLG between the metallic contacts and a layer of MoS2 reduces the Schottky barrier height dramatically for the low-work function metals (313 and 260 meV for Ti and Cr, respectively) while it increases for the high-work function one ( 160 meV for Pd), corresponding to an improved pinning factor. Our results provide a straightforward method to generate atomically thin dielectrics with applications not only for depinning the Fermi level at metal/transition metal dichalcogenide (TMD) interfaces but also for solving many other problems in electronics and optoelectronics
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