As-grown transition metal dichalcogenides
are usually chalcogen deficient and therefore contain a high density
of chalcogen vacancies, deep electron traps which can act as charged
scattering centers, reducing the electron mobility. However, we show
that chalcogen vacancies can be effectively passivated by oxygen,
healing the electronic structure of the material. We proposed that
this can be achieved by means of surface laser modification and demonstrate
the efficiency of this processing technique, which can enhance the
conductivity of monolayer WSe<sub>2</sub> by ∼400 times and
its photoconductivity by ∼150 times