Isolated molecular dopants in pentacene observed by scanning tunneling microscopy

Sieu D. Ha, Antoine Kahn

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31 Scopus citations

Abstract

Doping is essential to the control of electronic structure and conductivity of semiconductor materials. Whereas doping of inorganic semiconductors is well established, doping of organic molecular semiconductors is still relatively poorly understood. Using scanning tunneling microscopy, we investigate, at the molecular scale, surface and subsurface tetrafluoro-tetracyanoquinodimethane p -dopants in the prototypical molecular semiconductor pentacene. Surface dopants diffuse to pentacene vacancies and appear as negatively charged centers, consistent with the standard picture of an ionized acceptor. Subsurface dopants, however, have the effect of a positive charge, evidence that the donated hole is localized by the parent acceptor counterion, in contrast to the model of doping in inorganic semiconductors. Scanning tunneling spectroscopy shows that the electron potential energy is locally lowered near a subsurface dopant feature, in agreement with the localized hole model.

Original languageEnglish (US)
Article number195410
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume80
Issue number19
DOIs
StatePublished - Nov 13 2009

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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