Semiconductor and Dimensional Metrology Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20878, United States.
ACS Appl Mater Interfaces. 2015 Jan 21;7(2):1180-7. doi: 10.1021/am506921y. Epub 2015 Jan 6.
In this work, we compare the electrical characteristics of MoS2 field-effect transistors (FETs) with Ag source/drain contacts with those with Ti and demonstrate that the metal-MoS2 interface is crucial to the device performance. MoS2 FETs with Ag contacts show more than 60 times higher ON-state current than those with Ti contacts. In order to better understand the mechanism of the better performance with Ag contacts, 5 nm Au/5 nm Ag (contact layer) or 5 nm Au/5 nm Ti film was deposited onto MoS2 monolayers and few layers, and the topography of metal films was characterized using scanning electron microscopy and atomic force microscopy. The surface morphology shows that, while there exist pinholes in Au/Ti film on MoS2, Au/Ag forms a smoother and denser film. Raman spectroscopy was carried out to investigate the metal-MoS2 interface. The Raman spectra from MoS2 covered with Au/Ag or Au/Ti film reveal that Ag or Ti is in direct contact with MoS2. Our findings show that the smoother and denser Au/Ag contacts lead to higher carrier transport efficiency.
在这项工作中，我们比较了具有 Ag 源/漏极接触的 MoS2 场效应晶体管 (FET) 和具有 Ti 的 FET 的电学特性，并证明了金属-MoS2 界面对于器件性能至关重要。具有 Ag 接触的 MoS2 FET 的导通电流比具有 Ti 接触的 MoS2 FET 高 60 多倍。为了更好地理解 Ag 接触具有更好性能的机制，将 5nm Au/5nm Ag（接触层）或 5nm Au/5nm Ti 薄膜沉积到 MoS2 单层和多层上，并使用扫描电子显微镜和原子力显微镜对金属薄膜的形貌进行了表征。表面形貌表明，虽然 MoS2 上的 Au/Ti 薄膜存在针孔，但 Au/Ag 形成了更平滑和更致密的薄膜。进行了拉曼光谱分析以研究金属-MoS2 界面。来自覆盖有 Au/Ag 或 Au/Ti 薄膜的 MoS2 的拉曼光谱表明 Ag 或 Ti 与 MoS2 直接接触。我们的研究结果表明，更平滑和更致密的 Au/Ag 接触导致更高的载流子输运效率。
