Issue 18, 2022

Direct observation of narrow electronic energy band formation in 2D molecular self-assembly

Abstract

Surface-supported molecular overlayers have demonstrated versatility as platforms for fundamental research and a broad range of applications, from atomic-scale quantum phenomena to potential for electronic, optoelectronic and catalytic technologies. Here, we report a structural and electronic characterisation of self-assembled magnesium phthalocyanine (MgPc) mono and bilayers on the Ag(100) surface, via low-temperature scanning tunneling microscopy and spectroscopy, angle-resolved photoelectron spectroscopy (ARPES), density functional theory (DFT) and tight-binding (TB) modeling. These crystalline close-packed molecular overlayers consist of a square lattice with a basis composed of a single, flat-adsorbed MgPc molecule. Remarkably, ARPES measurements at room temperature on the monolayer reveal a momentum-resolved, two-dimensional (2D) electronic energy band, 1.27 eV below the Fermi level, with a width of ∼20 meV. This 2D band results from in-plane hybridization of highest occupied molecular orbitals of adjacent, weakly interacting MgPc's, consistent with our TB model and with DFT-derived nearest-neighbor hopping energies. This work opens the door to quantitative characterisation – as well as control and harnessing – of subtle electronic interactions between molecules in functional organic nanofilms.

Graphical abstract: Direct observation of narrow electronic energy band formation in 2D molecular self-assembly

Supplementary files

Article information

Article type
Paper
Submitted
16 jun 2022
Accepted
20 jul 2022
First published
17 aug 2022
This article is Open Access
Creative Commons BY-NC license

Nanoscale Adv., 2022,4, 3845-3854

Direct observation of narrow electronic energy band formation in 2D molecular self-assembly

J. Hellerstedt, M. Castelli, A. Tadich, A. Grubišić-Čabo, D. Kumar, B. Lowe, S. Gicev, D. Potamianos, M. Schnitzenbaumer, P. Scigalla, S. Ghan, R. Kienberger, M. Usman and A. Schiffrin, Nanoscale Adv., 2022, 4, 3845 DOI: 10.1039/D2NA00385F

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