  Scalable methods for improving the performance and stability of a
field-effect transistor (FET) based on two-dimensional materials are crucial
for its real applications. A scalable method of encapsulating the exfoliated
MoS$ _{2} $ on SiO$ _{2} $/Si substrate by hexamethyldisilazane (HMDS) is
explored here for reducing the influence of interface traps and ambient
contaminants. This leads to twenty-five times reduction in trap density, three
times decrease in subthreshold swing, three times increase in the peak
field-effect mobility and a drastic reduction in hysteresis. This performance
remains nearly the same after several weeks of ambient exposure of the device.
This is attributed to the superhydrophobic nature of HMDS and the SiO$_2$
surface hydrophobization by the formation of covalent bonds between the methyl
groups of HMDS and silanol groups of SiO$_{2}$.
