Temperature dependence of the partially localized state in a 2D molecular nanoporous network

Abstract

Two-dimensional organic and metal-organic nanoporous networks can scatter surface electrons, leading to their partial localization. Such quantum states are related to intrinsic surface states of the substrate material. We further corroborate this relation by studying the thermally induced energy shifts of the electronic band stemming from coupled quantum states hosted in a metalorganic array formed by a perylene derivative on Cu(111). We observe by angle-resolved photoemission spectroscopy (ARPES), that both, the Shockley and the partially localized states, shift by the same amount to higher binding energies upon decreasing the sample temperature, providing evidence of their common origin. Our experimental approach and results further support the use of surface states for modelling these systems, which are expected to provide new insight into the physics concerning partially confined electronic states: scattering processes, potential barrier strengths, excited state lifetimes or the influence of guest molecules.

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

“…It is straightforward to confirm that the 2DEG renormalization is correct since both the simulated band structure and the isoenergetic cuts fit well the experimental data when using the scattering parameters indicated in Model 2 of table 1. In figure 3(a), the second derivative of the experimental data (raw data in figure S2) exhibits the expected shallow dispersive bands of QD arrays [20,22,23,27]. The lower energy band corresponding to n=1 PLS has a ∼80meV bandwidth and shifts ∼150meV towards E F with respect to the pristine Cu SS and increases m * to~m 0.58 0 [20,23,32].…”

“…The organometallic network that we study is formed by deposition of the organic dye DPDI (4,9diaminoperylene quinone-3,10-diimine), which undergoes a dehydrogenation process when deposited on Cu(111) and heated to 250°C. The resulting organic building block 3deh-DPDI is an 'exo-ligand' coordinated to Cu adatoms that forms a long-range ordered, commensurate MONN [20,22,[29][30][31][32][33]36]. The unit cell is composed of 3 molecules and 6 Cu adatoms.…”

“…When the arrays are periodic and long-ranged, they generate characteristic shallow dispersive bands [20,21]. These surface specific electronic bands originating from the pristine Shockley state [22] can be delicately tuned by increasing the QD barrier separation (thus reducing the interpore coupling) [23], pore size [19] and also by changing the pore shape [24].…”

“…This raises the question whether such (to some extent arbitrary) assumptions are necessary when simulating the electron confinement by these MONNs. Here, we address this question by studying in detail the interaction between the 3deh-DPDI network [20,22,25,[29][30][31][32][33] and the Cu(111) 2DEG. Based on a combination of scanning tunneling microscopy and spectroscopy (STM and STS), angle-resolved photoemission (ARPES) and Kelvin probe force microscopy (KPFM) measurements, together with EPWE simulations, we demonstrate that both local confinement effects and the emergence of electronic bands induced by interpore coupling can be satisfactorily reproduced.…”

Adsorbate-Induced Modification of the Confining Barriers in a Quantum Box Array

“…3). This difference presumably arises from the temperature dependence of the energy of the QBS: the higher the temperature the more the confined state shifts towards lower BE 46 , the Shockley surface state 47 shifts likewise (note that the STS data were acquired at 4.2 K, whereas the ARPES data at room temperature). Additionally an uncertainty in Fermi level determination of ±10 meV needs to be taken into account.…”