Influence of halogen substitutions on rates of charge tunneling across SAM-based large-area junctions

Abstract

This paper examines the ability of structural modifications using halogen atoms (F, Cl, Br, and I) to influence tunneling rates across self-assembled monolayer (SAM)-based junctions having the structure Ag^TS/S(CH₂)_n(p-C₆H₄X)//Ga₂O₃/EGaIn, where S(CH₂)_n(p-C₆H₄X) is a SAM of benzenethiol (n = 0) or benzyl mercaptan (n = 1) terminated in a hydrogen (X = H) or a halogen (X = F, Cl, Br, or I) at the para-position. The measured tunneling current densities (J(V); A cm⁻²) indicate that replacing a terminal hydrogen with a halogen atom at the X//Ga₂O₃ interface leads to a decrease in J(V) by ∼×13 for S(p-C₆H₄X) and by ∼×50 for SCH₂(p-C₆H₄X). Values of J(V) for the series of halogenated SAMs were indistinguishable, indicating that changes in dipole moment and polarizability caused by introducing different halogen atoms at the interface between the SAM and the Ga₂O₃/EGaIn electrode do not significantly influence the rates of charge tunneling across the junctions.