Evolutionary structure prediction of two-dimensional IrB₁₄: A promising gas sensor material

Two-dimensional (2D) boron structures, in which boron atoms arrange in a 2D manner, have attracted great attention for their potential applications in nanoelectronic devices. To improve the stability of 2D boron and find new functionalities, we predict a series of sandwich-shaped 2D structures of IrB_x (8 ≤ x ≤ 16) through employing an ab initio evolutionary structure search. It is demonstrated that the stability of 2D boron sheets is greatly improved with the introduction of Ir atoms. Among various compositions, it turns out that 2D IrB₁₄ is thermodynamically more stable than a mixture of the known IrB₉ compound and α-boron. Moreover, we have studied the gas sensitivity of 2D-IrB₁₄ to the adsorption of CO and CO₂ molecules. It has been found that CO gas molecules bind chemically to boron atoms, whereas CO₂ molecules do not. Upon CO adsorption, there is a charge transfer from surface atoms to CO molecules. Hence, acceptor states are formed above the Fermi energy, indicating that IrB₁₄ is a promising novel 2D gas sensor material.