Prediction of single-layer antimony oxyselenide (Sb₂O₂Se₂): metal-to-semiconductor transition via hydrogenation

Abstract

In this study, the structural, electronic, vibrational, and mechanical properties of single-layer
Antimony Oxyselenide (Sb 2 O 2 Se 2 ) and its hydrogenated structure (Sb 2 O 2 Se 2 H 2 ) are investigated
by performing density functional theory-based first principles calculations. Geometry optimizations
reveal that single-layer Sb 2 O 2 Se 2 crystallizes in tetragonal structure which is shown to possess
dynamical stability by means of phonon band dispersions. In addition, the mechanical stability of
the predicted single layer is satisfied via the linear-elastic parameters. Electronically, it is revealed
that single-layer Sb 2 O 2 Se 2 exhibits metallic behavior whose highest occupied states are found to
arise from the surface Se atoms, may be an indication for tuning the electronic features via surface
functionalization. For the surface modification of Sb 2 O 2 Se 2 , top of each Se atom is saturated with
a H atom and fully hydrogenated single-layer Sb 2 O 2 Se 2 H 2 is shown to be an in-plane anisotropic
structure. In addition, it is found that the existence of tilted H atoms on the surface can be detected
via Scanning Tunneling Microscopy (STM) images. Phonon band dispersion calculations indicate the
dynamical stability of Sb 2 O 2 Se 2 H 2 . Mechanically stable Sb 2 O 2 Se 2 H 2 is found to possess anisotropic
linear-elastic behavior, which is much softer than its pristine structure. Moreover, electronically a
metallic-to-semiconducting transition is shown to occur as the unoccupied Se-orbitals are saturated
via H atoms. Our work offers insights into prediction of a novel single-layer material, namely
Sb 2 O 2 Se 2 , and reports the chemically-driven semiconducting behavior via hydrogenation, which may
lead to the use of hydrogenated structure in solar cell, photoelectrode, or photocatalyst applications.