Molecular Transistors with Perpendicular Gate Field Architecture: A Strong Gate Field Effect

In this work we study the transport properties of molecular transistors with bridges based on 1,4-benzene-dithiol (BDT) and 2-nitro-1,4-benzene-dithiol (nitro-BDT) using ab initio electron propagator calculations that include electron correlations. In the proposed architecture of a transistor, the gate electric field is chosen to be perpendicular to the plane of a benzene ring. For the transistor with a BDT molecular bridge, strong negative differential resistance is found. This behavior does not exist in the traditional architecture where the gate field is parallel to the benzene ring plane. We find that the peak in the IV curves strongly depends on gate voltage. Our results show that the position of the peak shifts toward lower values of source-drain voltage with the gate voltage. A molecular transistor based on the nitro-BDT molecular bridge also reveals a strong negative differential resistance behavior. We find well-pronounced maxima and minima for both positive and negative values of source-drain voltages as well as gate electric fields. In addition, we find that the larger the positive values of a gate field, the narrower the peak (the peak/valley ratio is equal to 20). For larger values of the gate field, the peak location is closer to the origin (∼0.1 eV). These two features are important for applications. The explanations of these phenomena are given in terms of molecular orbitals.