Rethinking transition voltage spectroscopy within a generic taylor expansion view

Ayelet Vilan*, David Cahen, Eli Kraisler

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Transition voltage spectroscopy (TVS) has become an accepted quantification tool for molecular transport characteristics, due to its simplicity and reproducibility. Alternatively, the Taylor expansion view, TyEx, of transport by tunneling suggests that conductance-voltage curves have approximately a generic parabolic shape, regardless of whether the tunneling model is derived from an average medium view (e.g., WKB) or from a scattering view (e.g., Landauer). Comparing TVS and TyEx approaches reveals that TVS is closely related to a bias-scaling factor, V0, which is directly derived from the third coefficient of TyEx, namely, the second derivative of the conductance with respect to bias at 0 V. This interpretation of TVS leads to simple expressions that can be compared easily across primarily different tunneling models. Because the basic curve shape is mostly generic, the quality of model fitting is not informative on the actual tunneling model. However internal correlation between the conductance near 0 V and V0 (TVS) provides genuine indication on fundamental tunneling features. Furthermore, we show that the prevailing concept that V0 is proportional to the barrier height holds only in the case of resonant tunneling, while for off-resonant or deep tunneling, V0 is proportional to the ratio of barrier height to barrier width. Finally, considering TVS as a measure of conductance nonlinearity, rather than as an indicator for energy level spectroscopy, explains the very low TVS values observed with a semiconducting (instead of metal) electrode, where transport is highly nonlinear due to the relatively small, bias-dependent density of states of the semiconducting electrode.

Original languageAmerican English
Pages (from-to)695-706
Number of pages12
JournalACS Nano
Volume7
Issue number1
DOIs
StatePublished - 22 Jan 2013
Externally publishedYes

Keywords

  • TVS
  • Taylor expansion
  • alkyl phosphonic acids
  • bias scaling
  • molecular electronics
  • silicon

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