Contact resistance reduction in MoS2 FETs using ultra-thin TiO2 interfacial layers

High contact resistance (R_C) at metal-Molybdenum disulfide (MoS₂) interface obscures the intrinsic transport properties of MoS₂ [1] and limits its potential as a channel material for future CMOS technology. In this work, we report reduction in the effective Schottky barrier height (SBH) and contact resistance at the metal-MoS₂ interface using an ultra-thin TiO₂ interfacial layer (IL) resulting in higher (upto 11X) field-effect mobility. Our results show, not only a reduction (upto 10X) but also a nearly constant (~40 meV) SBH irrespective of the metal work function, unlike Ge/Si where TiO₂ unpins the Fermi-level [2]. XPS and UPS measurements suggest that low RC and constant effective SBH can be attributed to charge transfer at the TiO₂-MoS₂ interface such that the MoS₂ layer near the interface is doped n-type. Additional improvement in MoS₂ FET performance is demonstrated by using TiO₂ as a dielectric on top of the MoS₂ channel.