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Probing the interplay between geometric and electronic structure in a two-dimensional K–TCNQ charge transfer network

Authors :
Tien-Lin Lee
Luke A. Rochford
Phil J. Blowey
Daniel Warr
David Phillip Woodruff
David A. Duncan
Giovanni Costantini
Source :
Faraday Discussions. 204:97-110
Publication Year :
2017
Publisher :
Royal Society of Chemistry (RSC), 2017.

Abstract

Scanning tunnelling microscopy (STM), low energy electron diffraction (LEED), ultraviolet and soft X-ray photoelectron spectroscopy (UPS and SXPS) have been used to characterise the formation of a coadsorption phase of TCNQ and K on Ag(111), while the normal incident X-ray standing waves (NIXSW) technique has been used to obtain quantitative structural information. STM and LEED show that an ordered incommensurate phase is formed in which the K atoms are surrounded by four TCNQ molecules in a ‘windmill’ motif, characteristic of other metal/TCNQ phases, in which the nominal TCNQ : K stoichiometry is 1 : 1. UPS and SXPS data indicate the TCNQ is in a negatively-charged state. NIXSW results show that the carbon core of the TCNQ is essentially planar at a height above the Ag(111) surface closely similar to that found without coadsorbed K. In the presence of TCNQ the height of the K ions above the surface is significantly larger than on clean Ag(111), and the ions occupy sites above ‘holes’ in the TCNQ network. NIXSW data also show that the N atoms in the molecules must occupy sites with at least two different heights above the surface, which can be reconciled by a tilt or twist of the TCNQ molecules, broadly similar to the geometry that occurs in bulk TCNQ/K crystals.

Details

ISSN :
13645498, 13596640, and 03017249
Volume :
204
Database :
OpenAIRE
Journal :
Faraday Discussions
Accession number :
edsair.doi.dedup.....c61c1cf81a2a8a87ea68ceee08500225
Full Text :
https://doi.org/10.1039/c7fd00093f