  Spin-to-charge conversion is an essential requirement for the implementation
of spintronic devices. Recently, monolayers of semiconducting transition metal
dichalcogenides (TMDs) have attracted considerable interest for spin-to-charge
conversion due to their high spin-orbit coupling and lack of inversion symmetry
in their crystal structure. However, reports of direct measurement of
spin-to-charge conversion at TMD-based interfaces are very much limited. Here,
we report on the room temperature observation of a large spin-to-charge
conversion arising from the interface of Ni$_{80}$Fe$_{20}$ (Py) and four
distinct large area ($\sim 5\times2$~mm$^2$) monolayer (ML) TMDs namely,
MoS$_2$, MoSe$_2$, WS$_2$, and WSe$_2$. We show that both spin mixing
conductance and the Rashba efficiency parameter ($\lambda_{IREE}$) scales with
the spin-orbit coupling strength of the ML TMD layers. The $\lambda_{IREE}$
parameter is found to range between $-0.54$ and $-0.76$ nm for the four
monolayer TMDs, demonstrating a large spin-to-charge conversion. Our findings
reveal that TMD/ferromagnet interface can be used for efficient generation and
detection of spin current, opening new opportunities for novel spintronic
devices.
