Dong Mi-Mi, Zhang Guang-Ping, Li Zong-Liang, Wang Ming-Lang, Wang Chuan-Kui, Fu Xiao-Xiao
Shandong Key Laboratory of Medical Physics and Image Processing & Shandong Provincial Engineering and Technical Center of Light Manipulations, School of Physics and Electronics, Shandong Normal University, Jinan 250358, China.
Phys Chem Chem Phys. 2020 Dec 23;22(48):28074-28085. doi: 10.1039/d0cp04450d.
Monolayer C2N is promising for next-generation electronic and optoelectronic applications due to its appropriate band gap and high carrier efficiency. However, relative studies have been held back due to the lack of high-quality electrode contacts. Here, we comprehensively study the electronic and transport properties of monolayer C2N with a series of electrode materials (Al, Ti, Ni, Cu, Ag, Pt, V2C, Cr2C and graphene) by using the nonequilibrium Green's function (NEGF) method combined with density functional theory (DFT). The monolayer C2N forms Ohmic contacts with the Ti/Cu/Ag electrode material in both armchair and zigzag directions, whereas Ohmic contact is only formed in the zigzag direction of the C2N-Al field effect transistor. However, the C2N-Ni, -Pt, -V2C, -Mo2C, -graphene contact systems form n-type Schottky contacts in either the armchair or zigzag direction owing to the relatively strong Fermi level pinning (the pinning factor S = 0.32 in the armchair direction and S = 0.26 in the zigzag direction). By insertion of BN or graphene between the C2N and Pt electrode in the armchair direction of contact systems, the Fermi level pinning can be effectively weakened due to the suppression of metal-induced gap states. Conspicuously, an Ohmic contact is realized in the C2N field effect transistors with the BN-Pt electrode, suggesting a possible approach to fabricating high-performance devices. Our study is conducive to selecting appropriate electrode materials for C2N-based field effect transistors.
单层C2N因其合适的带隙和高载流子效率，在下一代电子和光电子应用方面颇具潜力。然而，由于缺乏高质量的电极接触，相关研究受到了阻碍。在此，我们采用非平衡格林函数（NEGF）方法结合密度泛函理论（DFT），全面研究了单层C2N与一系列电极材料（Al、Ti、Ni、Cu、Ag、Pt、V2C、Cr2C和石墨烯）的电学和输运性质。单层C2N在扶手椅型和锯齿型方向上与Ti/Cu/Ag电极材料形成欧姆接触，而在C2N-Al场效应晶体管的锯齿型方向上仅形成欧姆接触。然而，由于相对较强的费米能级钉扎（扶手椅型方向的钉扎因子S = 0.32，锯齿型方向的S = 0.26），C2N-Ni、-Pt、-V2C、-Mo2C、-石墨烯接触系统在扶手椅型或锯齿型方向上均形成n型肖特基接触。通过在接触系统的扶手椅型方向上于C2N和Pt电极之间插入BN或石墨烯，由于金属诱导能隙态的抑制，费米能级钉扎可得到有效减弱。值得注意的是，在具有BN-Pt电极的C2N场效应晶体管中实现了欧姆接触，这为制造高性能器件提供了一种可能的途径。我们的研究有助于为基于C2N的场效应晶体管选择合适的电极材料。
