Doping-induced negative differential conductance enhancement in single-molecule junction

Abstract It is very attractive to design molecular junctions with high negative differential conductance (NDC) behaviors, especially in lower bias regime. An effective strategy is developed to dramatically enhance the NDC behavior of single-molecule device based on the non-equilibrium Green's function (NEGF) method and ab initio calculations. The numerical results show that the π-σ-π type molecule, which consists of two identical thiolated arylethynylene connected by a non-conjugated segment (denoted as M0), possesses interesting NDC behavior at lower bias regime. Applying addition reactions doping H or halogen atoms (F, Cl or Br) on the triple bonds of M0 molecule, the NDC values of the molecular systems are dramatically enhanced to about one order and even to about 30 times in magnitude. More significantly, the occurring bias of the NDC behavior is further lowered when M0 molecule takes addition reaction with Cl 2 or Br 2 molecule. Our study shows that, doping with different atoms result in different electrode-molecule interactions, which further modulates the energies and the distributions of the conduction states of molecular junctions differently, and consequently influences on the transmission spectra as well as the NDC behaviors of molecular systems. A suitable amount of electrons and less electronegativity for the doping atom possessing induce more delocalized HOMO and HOMO-1 with larger electrode-molecule interactions as well as higher orbital energy, which consequently results in higher NDC behaviors at lower bias voltage.