The Rate of Charge Tunneling through Self-Assembled Monolayers Is Insensitive to Many Functional Group Substitutions

We show the preparation and electrical characterization of junctions of the structure AgTS/S(CH2)4CONH(CH2)2R//Ga2O3/EGaIn including a range of common aliphatic, aromatic, and heteroaromatic organic tail groups

Hyo Jae Yoon

2012

Scholarcy highlights

  • Targets for shaping the tunneling barriers of molecular junctions have included electron– donor–bridge–acceptor molecules, molecular quantum dot systems, aromatic molecules, and complex organic molecules with multiple functional groups
  • We demonstrate that the rate of charge transport across these self-assembled monolayers is surprisingly insensitive to changes in the structure of the organic molecules of which they are composed
  • This paper characterizes the rates of charge transport by tunneling across a series of molecules— arrayed in SAMs—containing a common head group and body4CONH(CH2)2-) and structurally varied tail groups; these molecules are assembled in junctions of the structure AgTS/SAM//Ga2O3/EGaIn
  • Over a range of common aliphatic, aromatic, and heteroaromatic organic tail groups, changing the structure of R does not significantly influence the rate of tunneling
  • The span of the rates of tunneling current was less than a factor of ~5 over the entire series. This very small response of charge transport to the structure of R suggests that rates of tunneling through SAMs are largely insensitive to differences in the electronic structures of R
  • This study has five useful features: i) It improves intuition concerning the types of molecular structures that influence the rate of charge transport across thin, insulating organic films. ii) It outlines a method to improve the accuracy and reliability of measurement of J(V) that intersperses calibration standards among measurements of new compounds. iii) It provides an extensive set of comparable data against which to test theories of charge tunneling in organic matter. iv) It will restrain the enthusiasm of speculation about the range of exotic electronic effects that may be achieved by engineering the structures of organic tunneling barriers. v) It, in combination with other studies, will suggest directions for research involving functional groups having electronic structures that will, influence rates of tunneling

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