title: Bias induced transition from an ohmic to a non-ohmic interface in supramolecular tunneling junctions with Ga2O3/EGaIn top electrodes.
abstract: This study describes that the current rectification ratio, R ≡ |J|(-2.0 V)/|J|(+2.0 V) for supramolecular tunneling junctions with a top-electrode of eutectic gallium indium (EGaIn) that contains a conductive thin (0.7 nm) supporting outer oxide layer (Ga2O3), increases by up to four orders of magnitude under an applied bias of >+1.0 V up to +2.5 V; these junctions did not change their electrical characteristics when biased in the voltage range of ±1.0 V. The increase in R is caused by the presence of water and ions in the supramolecular assemblies which react with the Ga2O3/EGaIn layer and increase the thickness of the Ga2O3 layer. This increase in the oxide thickness from 0.7 nm to ∼2.0 nm changed the nature of the monolayer-top-electrode contact from an ohmic to a non-ohmic contact. These results unambiguously expose the experimental conditions that allow for a safe bias window of ±1.0 V (the range of biases studies of charge transport using this technique are normally conducted) to investigate molecular effects in molecular electronic junctions with Ga2O3/EGaIn top-electrodes where electrochemical reactions are not significant. Our findings also show that the interpretation of data in studies involving applied biases of >1.0 V may be complicated by electrochemical side reactions which can be recognized by changes of the electrical characteristics as a function voltage cycling or in current retention experiments.
authors.affiliation: Laboratory of Supramolecular Chemistry and Technology, MESA + Research Institute, University of Twente, 7500 AE Enschede, The Netherlands. aldrik.velders@wur.nl.
authors.forename: Kim S
authors.initials: KS
authors.lastname: Wimbush
authors.forename: Raluca M
authors.initials: RM
authors.lastname: Fratila
authors.forename: Dandan
authors.initials: D
authors.lastname: Wang
authors.forename: Dongchen
authors.initials: D
authors.lastname: Qi
authors.forename: Cao
authors.initials: C
authors.lastname: Liang
authors.forename: Li
authors.initials: L
authors.lastname: Yuan
authors.forename: Nikolai
authors.initials: N
authors.lastname: Yakovlev
authors.forename: Kian Ping
authors.initials: KP
authors.lastname: Loh
authors.forename: David N
authors.initials: DN
authors.lastname: Reinhoudt
authors.forename: Aldrik H
authors.initials: AH
authors.lastname: Velders
authors.forename: Christian A
authors.initials: CA
authors.lastname: Nijhuis