Study of phosphorene nanoribbon for making nanotube selective gas sensor

Phosphorene nanoribbon (PNR) is a two-dimensional crystalline substance possessing semiconductor property, which makes it a new promising gas sensor. The gas sensing performance significantly depends on the adsorption mechanism and the strength of bonding between gas molecules and phosphorene atoms. Adsorption of a gas molecule onto PNR can be investigated through different parameters, such as interatomic energy, distance between atoms, and changes in the band gap energy of PNR. In this research, first, the PNR relaxation is carried out for minimum energy of whole structure. Second, the folding and tubing of PNR are investigated for their stability and minimum energy specification. Next, we constructed a phosphorene nanotube (PNT) by connecting two folded PNR that we called it unconventional PNT (UPNT). We compared conventional cylindrical PNT (CPNT) with UPNT for their energies and electrical properties. In the final step, as gas nanosensor, the gas sensing behavior and specifications of CPNT and UPNT are investigated in the presence of several gases. Since a phosphorene nanotube generally has a stable structure, the presence of gas molecules causes deformation of crystalline of structure and change in its electronic properties. For evaluating the sensing properties of CPNT and UPNT, their I-V characteristics, density of states and energy band diagrams are calculated and compared in the absence and presence of gas molecules. The adsorption of CO, , , NH, and  gas molecules onto UPNT and CPNT are done in detail. The results show that the sensitivity of UPNT gas sensor is higher than that of CPNT for detecting special gas molecules. We further investigated the amount of charge transfer utilizing the nonequilibrium Green’s function (NEGF) formalism which is applied on crystallized atomic configuration. 

Keywords:

Density functional theory (DFT) , Gas sensor , Nonequilibrium Green’s Function (NEGF) , Phosphorene Nanoribbon (PNR) , Phosphorene Nanotube (PNT)