Molecular assemblies on surfaces: towards physical and electronic decoupling of organic molecules

• Sabine Maier and
• Meike Stöhr

Beilstein J. Nanotechnol. 2021, 12, 950–956, doi:10.3762/bjnano.12.71

• physical and electronic decoupling have been developed in view of fundamental studies as well as application in devices. Ultrathin semiconducting or insulating decoupling layers can be epitaxially grown as mono- and multilayers on many metallic substrates by either physical or chemical vapor deposition

• substrate and the organic building blocks. Recently, two-dimensional (2D) materials, including hexagonal boron nitride (hBN) [22][23], graphene [24][25][26][27], and MoS2 [28], have emerged as monatomically thin decoupling layers. Van der Waals 2D materials are generally well suited due to their chemical

• these decoupling layers to the organic molecules and vice versa. This has the great advantage that these systems can still be examined by scanning tunneling microscopy (STM) and spectroscopy (STS), which gives insight into structural and electronic properties of individual molecules. For applications

Local stiffness and work function variations of hexagonal boron nitride on Cu(111)

• Abhishek Grewal,
• Yuqi Wang,
• Matthias Münks,
• Klaus Kern and
• Markus Ternes

Beilstein J. Nanotechnol. 2021, 12, 559–565, doi:10.3762/bjnano.12.46

• -BN/Cu(111) substrate. Keywords: decoupling layers; hexagonal boron nitride; local stiffness; Moiré superstructure; work function variation; Introduction Two-dimensional hexagonal boron nitride (h-BN) is among the list of materials that garnered tremendous interest following the exfoliation of mono

Reconstruction of a 2D layer of KBr on Ir(111) and electromechanical alteration by graphene

• Zhao Liu,
• Antoine Hinaut,
• Stefan Peeters,
• Sebastian Scherb,
• Ernst Meyer,
• Maria Clelia Righi and
• Thilo Glatzel

Beilstein J. Nanotechnol. 2021, 12, 432–439, doi:10.3762/bjnano.12.35

• , resulting in quasi free-standing graphene layers [18]. Alkali halide layers are frequently used as decoupling layers in surface science [19][20][21][22]. They are reported to form single- or double-layer islands with a typical cubic structure on single-crystalline transition metal surfaces [23][24

Controlling the electronic and physical coupling on dielectric thin films

• Philipp Hurdax,
• Michael Hollerer,
• Larissa Egger,
• Georg Koller,
• Xiaosheng Yang,
• Anja Haags,
• Serguei Soubatch,
• Frank Stefan Tautz,
• Mathias Richter,
• Alexander Gottwald,
• Peter Puschnig,
• Martin Sterrer and
• Michael G. Ramsey

Beilstein J. Nanotechnol. 2020, 11, 1492–1503, doi:10.3762/bjnano.11.132

• ), 10587 Berlin, Germany 10.3762/bjnano.11.132 Abstract Ultrathin dielectric/insulating films on metals are often used as decoupling layers to allow for the study of the electronic properties of adsorbed molecules without electronic interference from the underlying metal substrate. However, the presence

• of such decoupling layers may effectively change the electron donating properties of the substrate, for example, by lowering its work function and thus enhancing the charging of the molecular adsorbate layer through electron tunneling. Here, an experimental study of the charging of para-sexiphenyl

• monolayer and thus the charge density (σ) on the surface. For the capacitor model to be predictive and quantitative for ultrathin decoupling layers, a realistic value for their dielectric constant (εr) is required. This can be estimated from a molecular dosing series, such as in Figure 5. Figure 6b shows

Self-assembly and spectroscopic fingerprints of photoactive pyrenyl tectons on hBN/Cu(111)

• Domenik M. Zimmermann,
• Knud Seufert,
• Luka Ðorđević,
• Tobias Hoh,
• Sushobhan Joshi,
• Tomas Marangoni,
• Davide Bonifazi and
• Willi Auwärter

Beilstein J. Nanotechnol. 2020, 11, 1470–1483, doi:10.3762/bjnano.11.130

• properties in organic layers relied on bulk insulator supports [14][15][16]. As a promising alternative to bulk insulators, ultrathin dielectric films can act as decoupling layers but maintain the possibility to perform STM and STS measurements [17]. Atomically-thin hBN sheets attracted considerable interest

• (see Figure 6). Dissimilar responses of distinct MOs to work function variations were previously discussed, e.g., for pentacene on dielectric decoupling layers [23]. The assignment of the dI/dV signature to the MOs was corroborated by resolving the submolecular features in high-resolution STM images at

Monolayers of MoS₂ on Ag(111) as decoupling layers for organic molecules: resolution of electronic and vibronic states of TCNQ

• Asieh Yousofnejad,
• Gaël Reecht,
• Nils Krane,
• Christian Lotze and
• Katharina J. Franke

Beilstein J. Nanotechnol. 2020, 11, 1062–1071, doi:10.3762/bjnano.11.91

• screening by the substrate electrons. As a result, the energy levels are significantly broadened and molecular properties, such as vibrations are hidden within the spectral line shapes. Insertion of thin decoupling layers reduces the line widths and may give access to the resolution of electronic and

• of decoupling layers made use of the in situ fabrication of single layers of transition metal dichalcogenides on metal surfaces. A monolayer of MoS2 on Au(111) provided very narrow molecular resonances, close to the thermal resolution limit at 4.6 K [26]. The exquisite decoupling efficiency has been

• considerations may help when searching for appropriate decoupling layers for specific molecules. We have challenged the decoupling properties of MoS2/Ag(111) for TCNQ molecules. These exhibit their LUMO resonance just at the conduction band onset of MoS2, whereas the HOMO lies within the valence band. Hence, the

Adsorption and electronic properties of pentacene on thin dielectric decoupling layers

• Sebastian Koslowski,
• Daniel Rosenblatt,
• Alexander Kabakchiev,
• Klaus Kuhnke,
• Klaus Kern and
• Uta Schlickum

Beilstein J. Nanotechnol. 2017, 8, 1388–1395, doi:10.3762/bjnano.8.140

• 10.3762/bjnano.8.140 Abstract With the increasing use of thin dielectric decoupling layers to study the electronic properties of organic molecules on metal surfaces, comparative studies are needed in order to generalize findings and formulate practical rules. In this paper we study the adsorption and

• individual molecules on thin electronically decoupling layers. Depositing pentacene onto h-BN/Rh(111) results in significantly different adsorption characteristics, due to the topographic corrugation of the surface as well as the lateral electric fields it presents. These properties are reflected in the

• to sufficiently separate (electronically decouple) the molecules from the underlying metal substrate by means of thin insulating layers (decoupling layers) [6]. To achieve this, a thin spacer layer with a large band gap of several electronvolts can be used that acts as a tunnel barrier towards the