Scanning Tunneling Microscopy of the Organic Conductor [(η-C5Me5)2Ru(η66-[22](1, 4)-cyclophane)][TCNQ]4

Shulong Li, Henry S. White, Michael D. Ward

Research output: Contribution to journalArticle

Abstract

Scanning tunneling microscopy (STM) studies of the (001) and (010) faces, of the molecular semiconductor [(η-C5Me5)2Ru(η66-[22](1, 4)-cyclophane)]2+[TCNQ]42- (1, TCNQ = tetracyanoquinodimethane) are reported. The lattice constants determined from the density of states corrugation of the STM images are a = 13.8 ± 0.3 Å, b = 15.9 ± 0.2 Å, c = 16.6 ± 2 Å, β = 88° ± 2°, γ = 82° ± 2°, in good agreement with the X-ray crystal structure. STM images of both faces reveal local density of states (LDOS) associated with stacking of TCNQ molecules along the [100] direction in two crystallographically unique stacks. The tunneling current contrast conforms to the tetrameric periodicity of the TCNQ stacks observed in the crystal structure. Columnar regions of negligible tunneling current on the ac face are attributed to stacks of (η-C5Me5)2Ru(η66-[22](1, 4)cyclophane)2+ dications. Each TCNQ column exhibits a tunneling current corrugation repeating at intervals of a that is attributed to tunneling into the conduction band of antiferromagnetic 2κF charge density wave (CDW) structure. The CDWs also exhibit corrugation, and antiphase modulation, at a/2 with respect to adjacent stacks. This is consistent with appreciable interstack Coulomb interactions and contributions from the magnetic 4κF structure, which based on the tight-binding approximation is equivalent to the canonical description (TCNQ)2-(TCNQ)2-. The STM data are in agreement with magnetic susceptibility and EPR studies, which indicate significant contribution of the 4κF state to the electronic structure of 1. The STM therefore provides characterization of the local electronic structure that is manifested in the bulk electronic properties of 1.

Original languageEnglish (US)
Pages (from-to)1082-1091
Number of pages10
JournalChemistry of Materials
Volume4
Issue number5
DOIs
StatePublished - Feb 1 1992

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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