Bias induced transition from an ohmic to a non-ohmic interface in supramolecular tunneling junctions with Ga2O3/EGaIn top electrodes

K.S. Wimbush, R.M. Fratila, D.D. Wang, D.C. Qi, C. Liang, L. Yuan, N. Yakovlev, K.P. Loh, D.N. Reinhoudt, A.H. Velders, C.A. Nijhuis

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23 Citations (Scopus)

Abstract

This study describes that the current rectification ratio, R h equivalent to vertical bar J vertical bar(+2.0 V)/vertical bar J vertical bar(+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 similar 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.
Original languageEnglish
Pages (from-to)11246-11258
JournalNanoscale
Volume6
Issue number19
DOIs
Publication statusPublished - 2014

Keywords

  • self-assembled monolayers
  • host-guest interactions
  • single-molecule conductance
  • energy-level alignment
  • light-emitting-diodes
  • charge-transport
  • electrical-properties
  • liquid-metal
  • contacts
  • rectification

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    Wimbush, K. S., Fratila, R. M., Wang, D. D., Qi, D. C., Liang, C., Yuan, L., ... Nijhuis, C. A. (2014). Bias induced transition from an ohmic to a non-ohmic interface in supramolecular tunneling junctions with Ga2O3/EGaIn top electrodes. Nanoscale, 6(19), 11246-11258. https://doi.org/10.1039/c4nr02933j