Stability and electronic properties of XO (X = Be, Mg, Zn, Cd) biphenylene and graphenylene networks: A first-principles study

The ultrawide bandgap semiconducting property of materials is key to the development of advanced optoelectronic nanodevices with potential applications in flexible and transparent electronics and high-power radio frequency electronics. Here, a series of nonmagnetic porous XO (X = Be, Mg, Zn, and Cd) biphenylene- and graphenylene-type structures are predicted using the first-principles calculations based on the density functional theory (DFT). DFT results proved that XO monolayers exhibit excellent energetic, mechanical, dynamic, and thermal stabilities. The Heyd–Scuseria–Ernzerhof calculations show that the XO-biphenylene and graphenylene structures exhibit narrow, wide, ultra-wide, and insulating semiconducting electronic properties. We then investigated the bandgaps dependent on the thickness of the XO layer and found that the bandgaps decrease uniformly as the number of XO-biphenylene and -graphenylene layers increases. These remarkable electronic properties of XO structures expand the potential of porous oxide materials for the development of practical optoelectronic and thermoelectric nanodevices.