AB-stacked bilayer graphene zigzag nanoribbons: sensors for interlayer single molecule detection

A device is proposed consisting of a bilayer zigzag graphene nanoribbon (ZGNR) in AB stacking and β edge alignment to detect the presence of simple molecules in its interlayer space. Interlayer molecule detection is accomplished through analysis of the I-V characteristics of the device. Ab initio simulation is performed by applying spin-unpolarized density functional theory (DFT) and non-equilibrium Green’s function methods (NEGF) to the proposed model system. For interlayer molecule detection with improved sensitivity, we propose as model system a couple of AB-stacked ZGNR nanoribbons which are known to present edge states and edge magnetism at zero bias. For interlayer single molecules, we try CO, CO₂, and H₂O. Interlayer molecules induce local deformations into the ZGNR structure specific to each species and get efficiently trapped in the interlayer space experiencing subtle structural distortions under applied bias. I-V characteristics are fingerprints of molecules in the interlayer space displayed through negative differential resistance (NDR) phenomena and asymmetric behavior with respect to the sign of applied bias. The appearance of NDR can be understood in terms of the Landauer-Büttiker formalism. NDR in our device may be characterized as a rather weak and sharp one with a moderate peak current density. [Figure not available: see fulltext.]