Effect of halogenation on the electronic transport properties of aromatic and alkanethiolate molecules

Quantum transport calculations are conducted using nonequilibrium Green's functional formalism to study the effect of halogenation on the electronic transport properties of aromatic S-(C6H5)(2)X and alkanethiolate S-(CH2)(11)X molecules (with X = H, F, Cl, Br, or I) sandwiched between gold electrodes. In terms of conductance, both molecules show the same dependence on the halogen terminal groups despite their different electronic nature. For example, fluorination results in a reduction of the current by almost an order of magnitude, whereas iodine substitution leads to larger current as compared to the reference system (i.e. hydrogen termination). Regarding the asymmetry in the current-voltage characteristics, halogenation reduces the rectification level for the aromatic molecule with the smallest asymmetry for iodine termination. However, in the case of alkanethiolate molecule, halogen substitution increases the current rectification except for fluorination. A physical explanation of these results is obtained from the analysis of the behavior of the density of states, transmission spectra and transmission eigenstates. These findings are of practical importance in exploring the potential of halogenation for creating functional molecular self-assemblies on metallic substrates.

Automated summary

Using non-equilibrium Green's functional formalism, quantum transport calculations were conducted to study the effect of halogenation on the electronic transport properties of aromatic and alkanethiolate molecules. The results show that different halogen terminal groups have the same influence on conductance but different effects on the asymmetry of the current-voltage characteristics. The explanation of these results can be obtained from the analysis of density of states, transmission spectra and transmission eigenstates.