Novel two-dimensional square-structured diatomic group-IV materials: the first-principles prediction

This work presents a study of novel two-dimensional (2D) square-structured diatomic group-IV materials through density functional theory calculations. Our optimized structures have a planar structure. Moreover, we evaluate the structural stabilities and electronic properties of six square-structured 2D-diatomic XY (X, Y = C, Si, Ge, Sn) materials. In comparison, we also evaluate the honeycomb structure of those materials. The Birch-Murnaghan equation of states (BM-EOS) curves and cohesive energy evaluations indicate that the square-structured SnGe and SnSi materials are highly stable. Interestingly, most of the square-structured materials are dynamically stable based on phonon dispersion evaluation, except SnC material. More importantly, most of the square-structured materials have a narrower bandgap energy which implies better electronic properties. In particular, square-structured SnGe shows an ultra-wide bandgap of 4.02 eV which is prospective for future electronics. Furthermore, we believe that the stable square structures will be observed in the experiment and will be beneficial for future device applications.