title: Effect of molecular binding to a semiconductor on metal/molecule/semiconductor junction behavior.
abstract: Diodes made by (indirectly) evaporating Au on a monolayer of molecules that are adsorbed chemically onto GaAs, via either disulfide or dicarboxylate groups, show roughly linear but opposite dependence of their effective barrier height on the dipole moment of the molecules. We explain this by Au-molecule (electrical) interactions not only with the exposed end groups of the molecule but also with its binding groups. We arrive at this conclusion by characterizing the interface by in situ UPS-XPS, ex situ XPS, TOF-SIMS, and Kelvin probe measurements, by scanning microscopy of the surfaces, and by current-voltage measurements of the devices. While there is a very limited interaction of Au with the dicarboxylic binding groups, there is a much stronger interaction with the disulfide groups. We suggest that these very different interactions lead to different (growth) morphologies of the evaporated gold layer, resulting in opposite effects of the molecular dipole on the junction barrier height.
authors.affiliation: Department of Materials and Interfaces and Chemical Support Services, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Hossam
authors.initials: H
authors.lastname: Haick
authors.forename: Jamal
authors.initials: J
authors.lastname: Ghabboun
authors.forename: Olivia
authors.initials: O
authors.lastname: Niitsoo
authors.forename: Hagai
authors.initials: H
authors.lastname: Cohen
authors.forename: David
authors.initials: D
authors.lastname: Cahen
authors.forename: Ayelet
authors.initials: A
authors.lastname: Vilan
authors.forename: Jaehyung
authors.initials: J
authors.lastname: Hwang
authors.forename: Alan
authors.initials: A
authors.lastname: Wan
authors.forename: Fabrice
authors.initials: F
authors.lastname: Amy
authors.forename: Antoine
authors.initials: A
authors.lastname: Kahn