Anisotropies in the electrical properties of rod-like aggregates of liquid crystalline phthalocyanines: Direct current conductivities and field-effect mobilities

Carrie L. Donley, R. A.P. Zangmeister, Wei Xia, Britt Minch, Anthony Drager, Samir K. Cherian, Lynn LaRussa, Bernard Kippelen, Benoit Domercq, David L. Mathine, David F. O'Brien, Neal R. Armstrong

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

The direct current (dc) conductivities and organic field-effect transistor (OFET) characteristics of a class of octa-substituted liquid crystalline (discotic mesophase) phthalocyanines (Pcs) are discussed. These molecules self-organize into columnar aggregates with large coherence lengths (up to approximately 300 nm). Langmuir-Blodgett films of these molecules were horizontally transferred to either interdigitated microelectrodes (IME) or OFET substrates, so that current flow could be measured either parallel or perpendicular to the column axis. Twenty-eight bilayer films of these Pcs on the IME substrates showed anisotropies in dc conductivity up to 50:1, whereas similar Pc films showed anisotropies in field effect mobilities of approximately 10:1, for a variety of W/L ratios (source/drain dimensions and spacing). Field-effect mobilities of 1 to 5 × 10-6 cm2·V-1·s-1 were determined from OFET measurements, along the Pc column axis, whereas charge mobilities measured from the space charge limited current regime on the IME substrates were in the range of 10-4 cm2·V-1·s-1. Conductive tip atomic force microscopy measurements on the apprximately 500-nm length scale showed that the conductivity anisotropy can be as high as 1000:1 when the Pc columns are intimately contacted to an adjacent Au bond pad.

Original languageEnglish (US)
Pages (from-to)2087-2099
Number of pages13
JournalJournal of Materials Research
Volume19
Issue number7
DOIs
StatePublished - Jul 1 2004

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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    Donley, C. L., Zangmeister, R. A. P., Xia, W., Minch, B., Drager, A., Cherian, S. K., LaRussa, L., Kippelen, B., Domercq, B., Mathine, D. L., O'Brien, D. F., & Armstrong, N. R. (2004). Anisotropies in the electrical properties of rod-like aggregates of liquid crystalline phthalocyanines: Direct current conductivities and field-effect mobilities. Journal of Materials Research, 19(7), 2087-2099. https://doi.org/10.1557/JMR.2004.0278