Effective determination of surface potential landscapes from metal-organic nanoporous network overlayers

Abstract

Determining the scattering potential landscape for two-dimensional superlattices provides key insight into fundamental quantum electron phenomena. Theoretical and semiempirical methods have been extensively used to simulate confinement effects of the two-dimensional electron gas (2DEG) on superlattices with a single scatterer in the form of vicinal surfaces and dislocation networks or isolated structures such as quantum corrals and vacancy islands. However, the complexity of the problem increases when the building blocks (or scatterers) are heterogeneous, as in metal-organic nanoporous networks (MONNs), since additional potentials may come into play. Therefore, the parametrization of the surface potential landscape is often inaccurate, leading to incorrect scattering potentials. Here, we address this issue with a combination of scanning tunneling microscopy/spectroscopy, angle resolved photoemission spectroscopy and Kelvin probe force microscopy measurements together with electron plane-wave expansion simulations on a MONN grown on Cu(111). This experimentaltheory approach, enables us to capture the 2DEG response to the intricate scattering potential landscape, and reveals systematic modeling procedures. Starting from a realistic geometry of the system, we determine the repulsive scattering potentials for both molecules and coordinated metal adatoms, the latter contradicting the established simulation framework. Moreover, we reveal local asymmetries and subtle renormalization effects of the 2DEG that relate to the interaction of the MONN and the underlying substrate.

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

“…Our simulations agree simultaneously with the ARPES and STS datasets when using the geometry shown in the inset of Fig. 2(f) (constructed from the chemical model structure of the MONN) and assuming two different scattering regions: highly repulsive for molecules (V mol ¼ 250 meV in green) and weakly repulsive around the Cu adatoms (V Cu ¼ 50 meV in dark blue) [1,3,5] (Fig. S5 shows the effect in the band structure when tweaking these potential values).…”

“…This identification of the LDOS features allows us to explicitly correct the To shed light into the surface potential landscape that TPyB-Cu entails for the 2DEG, we perform EPWE simulations. This semiempirical method has been successfully used to obtain the confining character of related nanoporous networks [1,[3][4][5]. Our simulations agree simultaneously with the ARPES and STS datasets when using the geometry shown in the inset of Fig.…”

“…Each pore acts as a quantum dot (QD) and their properties are tunable by proper selection of the building units. These building units dictate the effective potential barriers [5][6][7], the geometry of the array [4], and the existing interaction with the substrate [7,8] defining the ultimate confining capabilities of the system. Metal-organic nanoporous networks (MONNs) are possibly the most versatile and robust of noncovalent organic arrays when compared to other related electrostatically bonded (hydrogen or halogen) networks [1][2][3][4][9][10][11].…”

Near Fermi Superatom State Stabilized by Surface State Resonances in a Multiporous Molecular Network

“…Given the central pore’s hexagonal symmetry, we find the overbarrier resonances at corner and edge sites ( Figures S8P,Q ). Thus, we do not discard a SS-mediated growth scenario 23 , 29 in the formation of our complex network that would further stabilize the edge and corner mini-pores and compensate the relatively small dimerization energy found by DFT for the C–Br··· N halogen bonds. Likewise, the presence of edge and corner pores contributes with a minor energy reduction of the central pore SS resonance energy.…”

“…When applied to nanoporous molecular networks, these simulations provide the real-space LDOS (containing the confined SS resonances) and quantify both the strength of the potential barriers and the dispersion of the QD array band structures. 1 , 2 , 14 , 22 , 23 , 33 Since this modelization cannot consider the MOs, we take advantage of this limitation to discriminate the confined SS resonances from the SAMO states.…”