Carbon monoxide adsorption on different sub-lattice sites of nitrogen and phosphorous doped and Co-doped germanene- a first principle study

In this work, using first principle calculation, the Carbon Monoxide (CO) adsorption on Nitrogen (N), Phosphorus (P) doped, and co-doped monolayer Germanene (Ge) is theoretically investigated for the first time. In this context, emphasis has been given to the strength, stability, and effects of CO adsorption when the dopants species are introduced at different sub-lattice sites of the Ge lattice. The strength, stability, and effects of CO adsorption on pristine/(co-)doped Ge have been quantified from adsorption energy, recovery time, and charge transfer. Next, the CO adsorption and charge transfer at different doping configurations is analyzed from the local charge distributions at the adsorption site in presence of specific dopant atoms. The influence of CO adsorption on the electronic properties of the doped Ge has been assessed from the modulations in the bandgap and effective mass after adsorptions and analyzed from the relative contributions of adsorbed CO to the density of states profile. The results indicate CO is preferentially adsorbed on the Germanium atoms and accepts electrons from the lattice in both pristine and (co-)doped Ge. The pristine and P-doped Ge demonstrates physisorption, whereas N-doped and N/P co-doped Ge demonstrates chemisorption of CO. Moreover, the relative positions of (co-)dopants at different sub-lattice of Ge notably affect the adsorption energy and charge transfer, which are highest in N doped Ge. Finally, the N/P (co-) doping results in finite energy band bap opening and effective masses at the band edges, which are distinctly modulated after CO adsorptions for different (co-)doping configurations.