  In recent times, two dimensional (2D) ZnO has attracted a great attention in
the field of nano-research due to its extraordinary electronic, thermal and
optical properties. In this paper, we have explored the effects of halogen
impurity doping such as F, Cl, and Br atoms on the electronic properties of 2D
ZnO using first principles calculation. The pristine 2D ZnO exhibits a
semiconducting behavior with a direct bandgap of 1.67 eV on the {\Gamma} point.
However, when impurities such as F, Cl, or Br atoms are introduced, the 2D ZnO
shows semi-metallic behavior with almost zero bandgap. It is perceived that,
owing to the introduction of F impurity, the zero bandgap is exhibited at the K
point of the electronic band structure. However, in the case of Cl and Br
impurities, the nearly zero bandgap is observed elsewhere rather than on the K
point. Moreover, due to the introduction of impurity atoms, the Fermi level
also shifted towards the conduction band (CB) suggesting an increase of the
carrier concentration in the density of states (DOS) results. These findings
might be very much beneficial when doping effect, especially halogen impurity
doping is considered to modulate the electronic properties of 2D ZnO in the
near future.
