posted on 2021-11-02, 15:15authored byCheng Tang, Lei Zhang, Dimuthu Wijethunge, Kostya Ken Ostrikov, Aijun Du
Two-dimensional
(2D) ferroelectric In2Se3 with rarely discovered
out-of-plane polarization has great potentials
in advanced electronic and electromechanical applications. Considering
that point defects are ineluctable in practical applications and may
greatly influence the electronic properties, we systematically investigate
the stability, induced conductive type, and electric polarization
of defects in 2D In2Se3 (D-In2Se3) monolayers and In2Se3-graphene heterobilayers
through first principles calculations. Among the 40 kinds of considered
vacancies, the decentralized vacancy possesses relatively high stability.
In addition, the difficulty in migration of these vacancies leads
to the localized electronic effect. The n- and p-doped conditions
are, respectively, achieved by single In and surface Se vacancies
in the D-In2Se3 monolayers. Their out-of-plane
polarity can also be regulated by the types and concentrations of
vacancies due to the induced charge redistribution. More interestingly,
different from the perfect In2Se3–graphene
heterobilayer, where only n-type graphene can be achieved, the existence
of surface Se vacancies in the D-In2Se3 layer
can toggle the conductive type of the graphene layer between p- and
n-doped conditions by reversing its electric polarization, suggesting
the applications in the electric-controlled p–n junction. This
work establishes the theoretical foundation for the influence of intrinsic
vacancies on electronic and ferroelectric properties in the D-In2Se3 monolayer and heterobilayer, providing the
application guides on 2D ferroelectrics by defect engineering.