  To reduce Schottky-barrier-induced contact and access resistance, and the
impact of charged impurity and phonon scattering on mobility in devices based
on 2D transition metal dichalcogenides (TMDs), considerable effort has been put
into exploring various doping techniques and dielectric engineering using
$high-\kappa$ oxides, respectively. The goal of this work is to demonstrate a
$high-\kappa$ dielectric that serves as an effective n-type charge transfer
dopant on monolayer (ML) molybdenum disulfide ($MoS_{2}$). Utilizing amorphous
titanium suboxide (ATO) as the '$high-\kappa$ dopant', we achieved a contact
resistance of ~ $180$ ${\Omega}.{\mu}m$ which is the lowest reported value for
ML $MoS_{2}$. An ON current as high as $240$ ${\mu}A/{\mu}m$ and field effect
mobility as high as $83$ $cm^2/V-s$ were realized using this doping technique.
Moreover, intrinsic mobility as high as $102$ $cm^2/V-s$ at $300$ $K$ and $501$
$cm^2/V-s$ at $77$ $K$ were achieved after ATO encapsulation which are among
the highest mobility values reported on ML $MoS_{2}$. We also analyzed the
doping effect of ATO films on ML $MoS_{2}$, a phenomenon which is absent when
stoichiometric $TiO_{2}$ is used, using ab initio density functional theory
(DFT) calculations which shows excellent agreement with our experimental
findings. Based on the interfacial-oxygen-vacancy mediated doping as seen in
the case of $high-\kappa$ ATO - ML $MoS_{2}$, we propose a mechanism for the
mobility enhancement effect observed in TMD-based devices after encapsulation
in a $high-\kappa$ dielectric environment.
