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

DOI: 10.1039/C7FD00093F DOI Help

Authors: P. J. Blowey (Diamond Light Source; University of Warwick) , Luke A. Rochford (University of Warwick) , David Duncan (Diamond Light Source) , Daniel Warr (University of Warwick) , T.-l. Lee (Diamond Light Source) , D. P. Woodruff (University of Warwick) , Giovanni Costantini (University of Warwick)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Faraday Discuss.

State: Published (Approved)
Published: March 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 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.

Subject Areas: Chemistry, Materials


Instruments: I09-Surface and Interface Structural Analysis