Electron Transmission through Coordinating Atoms Embedded in Metal-Organic Nanoporous Networks

Ignacio Piquero-Zulaica, Ali Sadeghi, Mohammad Kherelden, Muqing Hua, Jing Liu, Guowen Kuang, Linghao Yan, J. Enrique Ortega, Zakaria M. Abd El-Fattah, Behnam Azizi, Nian Lin, and Jorge Lobo-Checa

Phys. Rev. Lett. 123, 266805 – Published 31 December 2019

Abstract

On-surface metal-organic nanoporous networks generally refer to adatom coordinated molecular arrays, which are characterized by the presence of well-defined and regular nanopores. These periodic structures constructed using two types of components confine the surface electrons of the substrate within their nanocavities. However, the confining (or scattering) strength that individual building units exhibit is a priori unknown. Here, we study the modification of the substrate’s surface electrons by the interaction with a Cu-coordinated TPyB metal-organic network formed on Cu(111) and disentangle the scattering potentials and confinement properties. By means of STM and angle-resolved photoemission spectroscopy we find almost unperturbed free-electron-like states stemming from the rather weak electron confinement that yields significant coupling between adjacent pores. Electron plane wave expansion simulations match the superlattice induced experimental electronic structure, which features replicating bands and energy renormalization effects. Notably, the electrostatic potential landscape obtained from our ab initio calculations suggests that the molecules are the dominant scattering entities while the coordination metal atoms sandwiched between them act as leaky channels. These metal atom transmission conduits facilitate and enhance the coupling among quantum dots, which are prone to be exploited to engineer the electronic structure of surface electron gases.

Received 29 July 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.266805

Physics Subject Headings (PhySH)

Chemical bonding Electronic structure of atoms & molecules Local density of states Surface states

Angle-resolved photoemission spectroscopy Scanning tunneling microscopy

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Ignacio Piquero-Zulaica ^1,2,3,*, Ali Sadeghi ^4,5,†, Mohammad Kherelden⁶, Muqing Hua ⁷, Jing Liu ⁷, Guowen Kuang⁷, Linghao Yan ⁷, J. Enrique Ortega^1,2,8, Zakaria M. Abd El-Fattah ⁶, Behnam Azizi⁴, Nian Lin⁷, and Jorge Lobo-Checa ^9,10,‡

¹Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, Manuel Lardizabal 5, E-20018 San Sebastián, Spain
²Donostia International Physics Center, Paseo Manuel Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
³Physik Department E20, Technische Universität München, 85748 Garching, Germany
⁴Department of Physics, Shahid Beheshti University, GC, Evin, 19839 Tehran, Iran
⁵School of Nano Science, Institute for Research in Fundamental Sciences (IPM), 19395-5531 Tehran, Iran
⁶Physics Department, Faculty of Science, Al-Azhar University, Nasr City, E-11884 Cairo, Egypt
⁷Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China
⁸Universidad del País Vasco, Dpto. Física Aplicada I, E-20018 San Sebastián, Spain
⁹Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, E-50009 Zaragoza, Spain
¹⁰Departamento de Física de la Materia Condensada, Universidad de Zaragoza, E-50009 Zaragoza, Spain

^*Corresponding author. ipiquerozulaica@gmail.com
^†Corresponding author. ali_sadeghi@sbu.ac.ir
^‡Corresponding author. jorge.lobo@csic.es

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 123, Iss. 26 — 31 December 2019

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
Topographic characterization of the TPyB-Cu metal-organic network. (a) High-resolution STM image of the single-domain Cu-coordinated TPyB-Cu hexagonal QD array grown on Cu(111). The inset shows the precursor molecule. (b) Enlargement into the hexagonal porous structure with a superimposed structural model. (c) LEED pattern of the network, which shows evidence that the molecular film is long-range ordered and single domain on the Cu(111) surface.
Reuse & Permissions
Figure 2
Electronic structure of the TPyB-Cu nanoporous network. Top row contains ARPES experimental datasets obtained at 150 K that compares the 2DEG of the pristine surface (a) with the TPyB-Cu network along the two high-symmetry directions: (b) $\bar{Γ M}$ and (c) $\bar{Γ K}$ . A down-shift of the band bottom (see dashed purple line) and replicating bands following the superperiodicity of the MONN (vertical dashed red lines) are observed. (d) EDCs at normal emission ( $\bar{Γ}$ point) for TPyB-Cu (red) exhibits a down-shift of $- 70 meV$ with respect to the pristine Cu SS (blue). (e) Local electronic structure at different MONN positions shown as STS $d I / d V$ spectra for the pore center (red), the molecule (green) and the Cu coordination atom (purple). These are simulated in (f) by EPWE as solid lines of the same colours using the scattering geometry depicted in the inset ( $V_{mol} = 250 meV$ and $V_{Cu} = 50 meV$ ). The down-shift of the experimental $d I / d V$ s [red vs gray vertical dashed lines in (e)] agrees with the ARPES observations in the upper row and is correctly reproduced by our EPWE simulations [overlaid white lines in (b) and (c) indicate EPWE band calculations]. (g) Power spectral functions of 2DEG along Cu to Cu direction that resembles the ARPES band structure along the $\bar{Γ K}$ direction shown in (c). (h) EPWE simulated 1D LDOS maps along the horizontal (molecule to molecule) and vertical (Cu to Cu) directions outlined in the inset of (f).
Reuse & Permissions
Figure 3
Electrostatic potential map calculations for TPyB-Cu [panels (a) and (b)] and comparison to the hologen-bonded Br-DNT network from Ref. [4] [panels (c) and (d)]. On the top of the panels, electrostatic potential contour plot maps corresponding to 3.08 Å (last surface layer) [(a) and (c)] and 2.36 Å planes [(b) and (d)] with respect to the average molecular backbone are shown. Beneath these, two perpendicular potential line profiles are extracted for each case, revealing the significant potential difference encountered by the 2DEG: Cu adatoms present conductive channels in TPyB-Cu, which are absent in the better confining Br-DNT network.
Reuse & Permissions

Physical Review Letters