Metallic contact induced van der Waals gap in a MoS FET

• Published in: Nanoscale 2019-10, Vol.11 (39), p.18246-18254
• Main Authors: Kim, Changsik, Lee, Kwang Young, Moon, Inyong, Issarapanacheewin, Sudarat, Yoo, Won Jong
• Format: Article
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c9nr04567h

Electrical metal contacts formed with 2D materials strongly affect device performance. Here, we used scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS) to characterize the interfacial structure formed and physical damage induced between MoS 2 and the most commonly used metals, Ti, Cr, Au, and Pd. We further correlated the electrical performance with physical defects observed at the 2D interfacial structure. The contact resistances were higher in the order of Ti, Au, Pd, and Cr contacts, but all 4-point probe mobilities measured with metals in contact with identical quadrilayer MoS 2 were ∼65 cm 2 V −1 s −1 , confirming the reliability of the devices. According to the STEM and EDS analyses, the Ti contact gave rise to a van der Waals gap between the clean quadrilayer MoS 2 and the Ti contact. By contrast, Cr migrated into MoS 2 while Mo and S counter-migrated into the SiO 2 substrate. Au and Pd formed glassy layers that resulted in the migration of Mo and S into the Au and Pd electrodes. These interfacial structures between MoS 2 and contact metals strongly correlated with the electrical performance of 2D MoS 2 FETs, providing practical guidelines to form van der Waals contacts. The electronic performance of 2D nano-devices is strongly dependent on the interface structure formed with electrically contacting metals.