  Gold-assisted mechanical exfoliation currently represents a promising method
to separate ultra-large (cm-scale) transition metal dichalcogenides (TMDs)
monolayers (1L) with excellent electronic and optical properties from the
parent van der Waals (vdW) crystals. The strong interaction between $Au$ and
chalcogen atoms is the key to achieve this nearly perfect 1L exfoliation yield.
On the other hand, it may affect significantly the doping and strain of 1L TMDs
in contact with Au. In this paper, we systematically investigated the
morphology, strain, doping, and electrical properties of large area 1L
$MoS_{2}$ exfoliated on ultra-flat $Au$ films ($0.16-0.21 nm$ roughness) and
finally transferred to an insulating $Al_{2}O_{3}$ substrate. Raman mapping and
correlative analysis of the $E'$ and $A1'$ peaks positions revealed a moderate
tensile strain ($0.2\%$) and p-type doping ($n=-0.25 \times 10^{13} cm^{-2}$)
of 1L $MoS_{2}$ in contact with $Au$. Nanoscale resolution current mapping and
current-voltage (I-V) measurements by conductive atomic force microscopy
(C-AFM) showed direct tunnelling across the 1L $MoS_{2}$ on $Au$, with a broad
distribution of tunnelling barrier values (from 0.7 to 1.7 eV) consistent with
the p-type doping of $MoS_{2}$. After the final transfer of $1L-MoS_{2}$ on
$Al_{2}O_{3}/Si$, the strain was converted to compressive ($-0.25\%$).
Furthermore, an n-type doping ($n=0.5 \times 10^{13} cm^{-2}$) was deduced by
Raman mapping and confirmed by electrical measurements of an $Al_{2}O_{3}/Si$
back-gated 1L $MoS_{2}$ transistor. These results provide a deeper
understanding of the $Au$-assisted exfoliation mechanisms and can contribute to
its widespread applications for the realization of novel devices and artificial
vdW heterostructures
