Thermodynamic Driving Forces for Substrate Atom Extraction by Adsorption of Strong Electron Acceptor Molecules

P. Ryan, P. J. Blowey, B. S. Sohail, L. A. Rochford, D. A. Duncan, T.-L. Lee, P. Starrs, G. Costantini, R. J. Maurer, J. Phys. Chem. C 126, 6082-6090 (2022)

"A quantitative structural investigation is reported, aimed at resolving the issue of whether substrate adatoms are incorporated into the monolayers formed by strong molecular electron acceptors deposited onto metallic electrodes. A combination of X-ray standing waves, STM, and DFT show that there is an energetic driving force for adatom incorporation into adsorbate structures of the strong acceptor F₄TCNQ on Ag(100) but not for the weaker acceptor TCNQ."

Alkali Doping Leads to Charge-Transfer Salt Formation in a Two-Dimensional Metal-Organic Framework

P. J. Blowey, B. Sohail, L. A. Rochford, T. Lafosse, D. A. Duncan, P. T. P. Ryan, D. A. Warr, T.-L. Lee, G. Costantini, R. J. Maurer, and D. P. Woodruff, ACS Nano 14, 7475-7483 (2020)

"We show that the insertion of alkali atoms can significantly change the structure and electronic properties of a metal-organic interface. Coadsorption of tetracyanoquinodimethane (TCNQ) and potassium on a Ag(111) surface leads to the formation of a two-dimensional charge transfer salt, with properties quite different to those of the two-dimensional Ag adatom TCNQ metal-organic framework formed in the absence of K doping. We establish a highly accurate structural model by combination of quantitative XSW, STM, and DFT calculations. Full agreement between the experimental data and the computational prediction of the structure is only achieved by inclusion of a charge-transfer-scaled dispersion correction in the DFT, which correctly accounts for the effects of strong charge transfer on the atomic polarizability of potassium. "