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

High contact resistance (R
_C
) at metal-Molybdenum disulfide (MoS
₂
) interface obscures the intrinsic transport properties of MoS
₂
[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-MoS
₂
interface using an ultra-thin TiO
₂
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 TiO
₂
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 TiO
₂
-MoS
₂
interface such that the MoS
₂
layer near the interface is doped n-type. Additional improvement in MoS
₂
FET performance is demonstrated by using TiO
₂
as a dielectric on top of the MoS
₂
channel.