Adsorption of transition-metal atoms on two-dimensional hexagonal boron nitride monolayer: A First-principles study

Abstract

Adsorption of transition-metal atoms on (3×3) two-dimensional (2D) hexagonal boron-nitride (h-BN) monolayer has been investigated using plane-wave ultrasoft pseudo potential method based on density functional theory. Main focus have been placed on modified optical and electronic properties of the BN monolayer due to presence of adsorbate atoms. We have systematically investigated the adsorption of transition-metals atoms including (Ni, Fe, Co, Mn, and Cr) and it was found that these transition-metal atoms can be chemically adsorbed on 2D h-BN monolayer and that the process of adsorption is mainly exothermic. Firstly we determined the electronic and optical properties of (3×3) 2D h-BN monolayer without any adsorbate and it was observed that the band gap is around 4.744 eV. Upon adsorption of transition atoms band gap energy is reduced (< 1 eV). During adsorption Cr and Ni adsorb on Nitrogen atom of BN while Mn, Fe and Co adsorb on boron atom of BN. Cr, Ni, Fe and Co easily adsorb on h-BN and Mn forms weak bond with BN monolayer. The absorption peak of h-BN without any adsorbate is around 6.5 × 10⁴ cm^-1, and it is reduced to 5.5 × 10⁴ cm^-1 when transition atoms are adsorbed on h-BN. In most cases transition-metal atoms adsorption process can introduce impurity states in the band gap of h-BN due to presence of valence electrons in s and d orbital, thereby band gap theory was reduced.