Sub-nanometer Thickness Research Articles

O−O Radical Coupling in Ultrathin Reconstructed Co6.8Se8 Nanosheets for Effective Oxygen Evolution and Zinc‐Air Batteries

AbstractDesigning ultrathin transition metal electrocatalysts with optimal surface chemistry state is crucial for oxygen evolution reaction (OER). However, the structure‐dependent electrochemical performance and the underlying catalytic mechanisms are still not clearly distinguished. Herein, we synthesize ultrathin Co6.8Se8 nanosheets (NSs) with subnanometer thickness by incorporating catalytically inactive selenium (Se) into ultrathin Co(OH)2, thereby switching the OER reaction pathway from adsorbate evolution mechanism (AEM) to oxide path mechanism (OPM). The prepared ultrathin Co6.8Se8 NSs exhibit an overpotential of 253 mV at 10 mA/cm2, outperforming the mostly reported Co‐based electrocatalysts. Advanced operando synchrotron spectroscopies and X‐ray absorption spectroscopy reveal the ultrathin Co6.8Se8 NSs, whose surface is reconstructed into Se‐doped Co(OH)2 during the OER process, could trigger direct O*−O* radical coupling rather than OOH* intermediates within AEM pathway thus lowering the energy input. Density functional theory calculations confirm that Co6.8Se8 NSs with shorter Co−Co bond length and stable Co−Se bond could optimize the rate‐determining step barrier via OPM pathway. Besides, rechargeable zinc‐air batteries based on Co6.8Se8 NSs exhibit excellent stability for more than 500 h of continuous charge–discharge cycles at 4 mA/cm2. The present study highlights the structural‐dependent switch of OER pathways and provides valuable insights for further development of ultrathin OER catalysts.

Nano-engineered the interfacial transition zone between recycled fine aggregates and paste with graphene oxide for sustainable cement composites

The high water absorption and porosity of recycled aggregate often led to a compromised interface transition zone (ITZ), thereby adversely impacting the mechanical properties and durability of recycled aggregate concrete. This research presents a feasible, straightforward, and targeted strategy to reinforce the ITZ between recycled fine aggregate (RFA) and paste by utilizing RFA particles adsorbed with graphene oxide (GO), termed WGO@RFA. The experimental outcomes demonstrate that incorporating WGO@RFA can enhance the 28-day compressive and flexural strengths of recycled mortars by approximately 25 % and 20 %, respectively, compared to mortars containing only RFA. Furthermore, it can decrease the water sorptivity and chloride ion diffusion coefficients of recycled mortars (28 days) by about 20 % and 27 %, respectively. Notably, using WGO@RFA particles offers significant advantages, such as enhanced mechanical strengths, reduced transport properties, and a densified microstructure within the ITZ, compared to the conventional method of modifying the cement matrix with GO and then binding it with RFA. Highlighting the application of WGO@RFA shows a targeted strengthening of the ITZ, as the sub-nanometer thickness of GO adsorbed on the uneven RFA surface facilitates localized cement hydration at the ITZ. The findings of this research offer novel avenues for reusing aggregate and developing sustainable concrete.

Biaxial Strain Transfer in Monolayer MoS2 and WSe2 Transistor Structures.

Monolayer transition metal dichalcogenides are intensely explored as active materials in 2D material-based devices due to their potential to overcome device size limitations, sub-nanometric thickness, and robust mechanical properties. Considering their large band gap sensitivity to mechanical strain, single-layered TMDs are well-suited for strain-engineered devices. While the impact of various types of mechanical strain on the properties of a variety of TMDs has been studied in the past, TMD-based devices have rarely been studied under mechanical deformations, with uniaxial strain being the most common one. Biaxial strain on the other hand, which is an important mode of deformation, remains scarcely studied as far as 2D material devices are concerned. Here, we study the strain transfer efficiency in MoS2- and WSe2-based flexible transistor structures under biaxial deformation. Utilizing Raman spectroscopy, we identify that strains as high as 0.55% can be efficiently and homogeneously transferred from the substrate to the material in the transistor channel. In particular, for the WSe2 transistors, we capture the strain dependence of the higher-order Raman modes and show that they are up to five times more sensitive compared to the first-order ones. Our work demonstrates Raman spectroscopy as a nondestructive probe for strain detection in 2D material-based flexible electronics and deepens our understanding of the strain transfer effects on 2D TMD devices.

Characterizing the Orderliness of Interfacial Water through Stretching Vibrations.

Spatial orderliness, which is the orderly structure of molecules, differs significantly between interfacial water and bulk water. Understanding this property is essential for various applications in both natural and engineered environments. However, the subnanometer thickness of interfacial water presents challenges for direct and rapid characterization of its structural orderliness. Herein, through molecular dynamics simulations and infrared spectral analysis of interfacial water in a graphene slit pore, we reveal a hyperbolic tangent relationship between the water ordering and its O-H stretching information in the infrared spectrum. Specifically, O-H symmetric stretching dominated in the highly ordered water structure, while a transition to the asymmetric stretching corresponded to an increase in the degree of disorder. Thus, the O-H stretching behavior could serve as a useful and quick assessment of the orderliness of interfacial water. This work provided insights into interfacial water's unique molecular network and structural dynamics and identified the stretching vibrations' key role in its degree of order, providing insight for fields such as nanotechnology, biology, and material science.

Quantum well oscillations in giant magnetoresistance and conductance with ferromagnetic free layer thickness in spin-valve structures with inverted [Co/Pt]n/Co reference layer

We present a study on the conductance and giant magnetoresistance effect in Co/Cu/(Co/Pt)4/Co/IrMn spin valves, where the inverted [Co/Pt]4/Co reference layer and the Co free layer exhibit fcc (111) and hcp (100) orientations along the z-axis. The term ’inverted’ refers to sub-nanometer thickness for both Co and Pt layers, with Pt having a smaller thickness compared to Co. By varying the thickness of the Co free layer from 0.3 to 3.2 nm, we observe oscillations in both in-plane and perpendicular conductance as well as giant magnetoresistance, displaying a superposition of two periods (2.6 and 3.7 monolayers of the Co free layer). First-principle calculations suggest that these oscillations can be attributed to quantum well states occurring in minority channels between fcc Co(111) and hcp Co(100) within multilayered structures of Co/Cu(111)/Co, thereby providing an opportunity for precise manipulation of spin electrons within sub-nanometer scale textured layers.

Sub-Nanometer Mono-Layered Metal-Organic Frameworks Nanosheets for Simulated Flue Gas Photoreduction.

The dilemma between the thickness and accessible active site triggers the design of porous crystalline materials with mono-layered structure for advanced photo-catalysis applications. Here, a kind of sub-nanometer mono-layered nanosheets (Co-MOF MNSs) through the exfoliation of specifically designed Co3 cluster-based metal-organic frameworks (MOFs) is reported. The sub-nanometer thickness and inherent light-sensitivity endow Co-MOF MNSs with fully exposed Janus Co3 sites that can selectively photo-reduce CO2 into formic acid under simulated flue gas. Notably, the production efficiency of formic acid by Co-MOF MNSs (0.85mmolg-1h-1) is ≈13 times higher than that of the bulk counterpart (0.065mmolg-1h-1) under a simulated flue gas atmosphere, which is the highest in reported works up to date. Theoretical calculations prove that the exposed Janus Co3 sites with simultaneously available sites possess higher activity when compared with single Co site, validating the importance of mono-layered nanosheet morphology. These results may facilitate the development of functional nanosheet materials for CO2 photo-reduction in potential flue gas treatment.

Real-time simultaneous refractive index and thickness mapping of sub-cellular biology at the diffraction limit

Mapping the cellular refractive index (RI) is a central task for research involving the composition of microorganisms and the development of models providing automated medical screenings with accuracy beyond 95%. These models require significantly enhancing the state-of-the-art RI mapping capabilities to provide large amounts of accurate RI data at high throughput. Here, we present a machine-learning-based technique that obtains a biological specimen’s real-time RI and thickness maps from a single image acquired with a conventional color camera. This technology leverages a suitably engineered nanostructured membrane that stretches a biological analyte over its surface and absorbs transmitted light, generating complex reflection spectra from each sample point. The technique does not need pre-existing sample knowledge. It achieves 10−4 RI sensitivity and sub-nanometer thickness resolution on diffraction-limited spatial areas. We illustrate practical application by performing sub-cellular segmentation of HCT-116 colorectal cancer cells, obtaining complete three-dimensional reconstruction of the cellular regions with a characteristic length of 30 μm. These results can facilitate the development of real-time label-free technologies for biomedical studies on microscopic multicellular dynamics.

DNA Framework-Templated Fabrication of Ultrathin Electroactive Gold Nanosheets.

Generally, two-dimensional gold nanomaterials have unique properties and functions that offer exciting application prospects. However, the crystal phases of these materials tend to be limited to the thermodynamically stable crystal structure. Herein, we report a DNA framework-templated approach for the ambient aqueous synthesis of freestanding and microscale amorphous gold nanosheets with ultrathin sub-nanometer thickness. We observe that extended single-stranded DNA on DNA nanosheets can induce site-specific metallization and enable precise modification of the metalized nanostructures at predefined positions. More importantly, the as-prepared gold nanosheets can serve as an electrocatalyst for glucose oxidase-catalyzed aerobic oxidation, exhibiting enhanced electrocatalytic activity (~3-fold) relative to discrete gold nanoclusters owing to a larger electrochemical active area and wider band gap. The proposed DNA framework-templated metallization strategy is expected to be applicable in a broad range of fields, from catalysis to new energy materials.

Atomic Layer Deposition for Tailoring Tamm Plasmon-Polariton with Ultra-High Accuracy

In this study, we demonstrate the potential capability to control Tamm plasmon-polaritons (TPP) by applying atomic layer deposition (ALD) as a highly precise technique for plasmonic applications. Applications in plasmonics usually require tens of nanometers or less thick layers; thus, ALD is a very suitable technique with monolayer-by-monolayer growth of angstrom resolution. Spectroscopic ellipsometry and polarized reflection intensity identified the TPP resonances in the photonic band gap (PBG) formed by periodically alternating silicon oxide and tantalum oxide layers. The sub-nanometer control of the Al2O3 layer by ALD allows precise tailoring of TPP resonances within a few nanometers of spectral shift. The employing of the ALD method for the fabrication of thin layers with sub-nanometer thickness accuracy in more complex structures proves to be a versatile platform for practical applications where tunable plasmonic resonances of high quality are required.

Nano-engineering the interfacial transition zone between recycled concrete aggregates and fresh paste with graphene oxide

The high water absorption and porosity of recycled concrete aggregates (RCA) typically result in a weak interface transition zone (ITZ), thus severely limiting the mechanical property and durability of the prepared concrete. This study proposes a targeted approach to improve the microstructure of ITZ through conformally coating graphene oxide (GO) on RCA (i.e., GO@RCA). The experimental results reveal that the 28-day compressive/splitting tensile strength of concrete increases by 27%/40%, when GO@RCA replaces RCA. The GO coating significantly reduces the water absorption coefficient and the total charge passed by 15.1% and 63.4%, respectively. To further explore the practical application of such a strategy, instead of direct coating GO on RCA in the case of GO@RCA, RCA is pre-wetted with GO (termed WGO@RCA) before mixing with cement. Interestingly, the data show similar results as the case of concrete containing GO@RCA, strongly indicating the locality of GO at ITZ for WGO@RCA. The enhancement of concrete’s mechanical and durability properties resulted from the sub-nanometer thickness of GO coating and the hydrophilic functional groups to promote cement hydration at ITZ locally.

Probing Gate Dielectrics for Two-Dimensional Electronics at Atomistic Scale Using Transmission Electron Microscope

Layered materials with thermodynamical stability and scalable atomic thickness provide a potential solution for insulators in 2-D electronics. The formation of high-quality van der Waals interfaces provides potential solutions to overcome the present limit of gate control. To enhance the reliability and robustness of the 2-D device, the investigation of degradation kinetics and fundamental physics of breakdown events of layered dielectrics at an atomistic scale is important. However, the sub-nanometer thickness of layered gate stacks and complex interface states affected by atomic/electronic structures of local defects, which makes the breakdown mechanism research challenging. Advanced characterization technique with simultaneous analysis of elements, energy, and structure at an atomistic scale is crucial. Transmission electron microscope (TEM) is such a powerful tool to analyze the morphology, chemical composition, crystal structure, and electronic structure. In this review, the breakdown mechanism of layered insulators is summarized and discussed in depth at the atomistic scale. The challenges, which are important for the development of layered gate insulators, are also discussed.

Surface and interface mediated magnetism in mesoscopic ceria@carbon core–shell structures

CeO2@C submicron core–shell structure was prepared by a two-step synthesis method, and the ceria shell thickness and its microstructure were precisely controlled by the precursor composition and annealing process. The results show that forming the thin ceria shell by aggregating nanoparticles on the surface of the carbon sphere is more favorable for forming ferromagnetism than merely dispersed ceria nanoparticles. The saturation magnetization increases with decreasing shell thickness, indicating the contributions of surfaces and interfaces to the magnetism. Furthermore, high-temperature reduction results in shell densification and the aggregation of defects at the surface. The spectroscopic and microscopic measurements reveal that in such cases, a continuous defect-rich area with a sub-nanometric thickness, doped with electrons extends over the whole surface of the mesostructure. The magnetic strength difference caused by adjusting the thickness of this defective layer from several nanometers to sub-nanometric width can reach 360 times, suggesting that the magnetization of these mesoscopic systems is related to the presence of these quasi-2D electron-rich regions on the surface. This study shows the applicability of giant orbital magnetism to mesoscopic systems, and the results can also provide a reference for the subsequent synthesis of magnetic materials.

Direct Patterning of ZnO Deposition By Atomic-Layer Additive Manufacturing Using a Safe and Economical Precursor

AS-ALD has the potential to overcome many of the challenges the semiconductor industry is facing by enabling self-aligned fabrication, instead of lithography’s cost, resit, equipment. Main challenges in AS-ALD are the need for pre-patterned substrates, defects outside of the desired growing area resulting from insufficient selectivity, and limited selection of substrate materials that allow deposition. [1, 2]To overcome these challenges, we chose for the first time the novelty of direct patterning with an AL-3D printer, also called atomic layer additive manufacturing (ALAM). 3D-printing is a flexible and efficient tool for reducing the cost and time spend for designing and manufacturing. AL-3D in principle functions similar to conventional g-ALD and the special design of nozzle led in producing direct patterning. All the commercially available precursors which have been used in g-ALD are compatible with our invented equipment and not only we can produce the same films conveniently but also this device allows us to use new precursors e.g. Zn(DMP)2 opening a new chemistry window. We have already deposited different materials TiO2, Pt, SiO2, Al2O3 successfully using TTIP, (MeCp)PtMe3, APTES, TMA as precursor. The ZnO process is very well behaved in ALD community as a diethylzinc (ZnEt2) precursor’s very high vapor pressure and its very high reactivity to water. Our attempts at reducing the amount of vapor delivered were successful in part but the results were not sufficiently reproducible, therefore we turned to the use of a new zinc precursor instead.In this work we focus on the new precursor Zn(DMP)2 instead of ZnEt2 for ZnO deposition. The Zn(DMP)2 has a very low vapor pressure, the ethyl groups are complemented by dimethylamino substituents that stabilize central zinc ion and thereby render the molecule less reactive to water. Our characterization results shows the deposited ZnO films with our new precursor has same structure and composition as with ZnEt2 with a constant growth rate of 1.0 Å per cycle. the crystals are oriented in a roughly isotropic manner.After testing Zn(DMP)2 in classical ALD we achieved to print homogeneous patterns with well-defined edges and uniform thicknesses among the whole pattern. The rough particulate deposits indicative of uncontrolled CVD-mode deposition obtained with the ZnEt2 + water reaction are completely absent of lines obtained from the Zn(DMP)2 + water reaction. Furthermore, we fabricate a metal oxide transistor MOSFET to demonstrate the practical applications of the device. Clark; K. Tapily; K.-H. Yu; T. Hakamata; S. Consiglio; D. O´Meara; C. Wajda; J. Smith; G. Leusink; Perspective: New Process Technologies Required for Future Device and Scaling. APL Mater. 2018, 6, 05203Fang; J. C. Ho, Area-Selective Atomic Layer Deposition: Conformal Coating, Subnanometer Thickness Control, and Smart Positioning. ACS Nano 2015, 9 (9), 8651-8654.

(Digital Presentation) Scalable Growth of Transition Metal Dichalcogenides for Next-Generation Nanoelectronics

Atomically-thin semiconducting transitional metal dichalcogenides (TMDCs) are promising channel materials for future ultra-scaled electronic devices due to their high electron mobility attained at sub-nanometer thickness. In particular, monolayer WS2 has shown the highest theoretical room temperature electron mobility among other semiconducting TMDCs as a result of its low effective mass. However, it is still challenging to grow large-area and strictly monolayer WS2 through the conventional chemical vapor deposition (CVD) due to the uncontrollable growth kinetics. In this work, we provide a modified CVD process to prepare the uniform and large-area monolayer TMDCs. Theoretical simulations were performed to understand the fundamental thermodynamically mechanism of the monolayer growth. The property-variation in TMDCs due to difference in electronic structure between different layers of TMDCs can be significantly reduced based on this new approach. This poses a reliable route for the scalable growth of monolayer TMDCs, which is essential for their reliable applications in nanoelectronic devices.

Giant Enhancement and Directional Second Harmonic Emission from Monolayer WS2 on Silicon Substrate via Fabry-Pérot Micro-Cavity.

Two-dimensional transition metal dichalcogenides (TMDs) possess large second-order optical nonlinearity, making them ideal candidates for miniaturized on-chip frequency conversion devices, all-optical interconnection, and optoelectronic integration components. However, limited by subnanometer thickness, the monolayer TMD exhibits low second harmonic generation (SHG) conversion efficiency (<0.1%) and poor directionality, which hinders their practical applications. Herein, we proposed a Fabry-Pérot (F-P) cavity formed by coupling an atomically thin WS2 film with a silicon hole matrix to enhance the SH emission. A maximum enhancement (∼1580 times) is achieved by tuning the excitation wavelength to be resonant with the microcavity modes. The giant enhancement is attributed to the strong electric field enhancement in the F-P cavity and the oscillator strength enhancement of excitons from suspended WS2. Moreover, directional SH emission (divergence angle ∼5°) is obtained benefiting from the resonance of the F-P microcavity. Our research results can provide a practical sketch to develop both high-efficiency and directional nonlinear optical devices for silicon-based on-chip integration optics.

Plasmonics-based gas sensor with photonic spin hall effect in broad terahertz frequency range under variable chemical potential of graphene.

Graphene monolayer of sub-nanometer thickness possesses strong metallic and plasmonic behavior in a broad terahertz (THz) frequency range. This plasmonic effect can be considerably manipulated when graphene layer is subjected to a variable chemical potential (Ef) via chemical doping or electrical gating. The strong adsorption characteristics of graphene layer is another important advantage. In this work, a photonic spin Hall effect (PSHE) based plasmonic sensor consisting of germanium prism, organic dielectric layer, and graphene monolayer is simulated and analyzed in THz range aiming at highly sensitive and reliable gas sensing. Modified Otto configuration and Kubo formulation for graphene at room temperature are considered. The sensor’s performance is examined in terms of figure of merit (FOM). The analysis indicates that under angular interrogation scheme of sensor operation, the FOM improves for smaller chemical potential (moderate doping) and higher THz frequency. Moreover, the influence of temperature on gas sensor’s performance (FOM) is negligible, which suggests that the sensor is capable of providing stable sensing performance against temperature variation. The sensor design is highly flexible in terms of selection of THz frequency as an alternative interrogation scheme (i.e., measuring the variation in spin-dependent shift peak value of PSHE spectrum upon change in gas medium refractive index) can also be implemented. It is found that there is no need to change the moderate doping of graphene monolayer (i.e., Ef remains around its normal value ~ 0.1 eV) as the sensitivity achievable with this alternative method has considerably greater magnitude at smaller THz frequency (e.g., 2 THz). The magnitudes of FOM (with angular interrogation method) and sensitivity (with alternative method) are found to be significantly greater for rarer gaseous media, which might possibly assist in early detection of airborne viruses such as SARS-Cov-2 (while using appropriate specificity method) and to measure the concentration of a particular gas in a given gaseous mixture.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11082-022-03626-7.

Graphene-Based Plasmonic Sensor at THz Frequency with Photonic Spin Hall Effect Assisted by Magneto-optic Phenomenon.

Graphene monolayer of sub-nanometer thickness shows strong metallic and plasmonic behavior in terahertz (THz) frequency range. This plasmonic effect varies considerably when graphene layer is placed under a magnetic field of appropriate strength. The strong adsorption characteristic of graphene layer is another advantage. In this work, a photonic spin Hall effect (PSHE)-based plasmonic sensor consisting of germanium prism, organic dielectric layer, and graphene monolayer is simulated and analyzed in THz aiming at highly sensitive and reliable sensing under variable magnetic field. Modified Otto configuration and magneto-optic effect in graphene are considered. The sensor’s performance is examined in terms of sensitivity, limit of detection (LOD), and figure of merit (FOM). The analysis indicates that LOD of the order of 10−5 RIU for gas sensing is achievable, which is finer than recently reported gas sensors based on different techniques. Further, the FOM improves when a larger magnitude of magnetic field is applied. The FOM is even greater for rarer gaseous media, which can make the sensor extremely useful in early detection of airborne viruses such as SARS-Cov-2 (while using appropriate specificity method) and to measure the concentration of a particular gas in a given gaseous mixture. The results further indicate that the same sensor design can be used for magnetic field detection while the FOM of magnetic field detection is significantly greater for rarer gaseous medium (e.g., air), which may enable the probe to be used in early detection of radiation leakage in nuclear reactors. For larger magnitudes of magnetic field, the corresponding LOD becomes finer.

Atomistic vs. continuum models of nanoporous elastic solid: Stress fields, size-dependent effective stiffness and surface constants

The method of classical molecular dynamics (MD) is applied to study the stress fields and effective elastic stiffness tensor of nanoporous materials. A continuum model for a nanoporous solid involving a surface layer of sub-nanometer thickness is proposed. Systematic comparisons of the unit cell atomistic MD results are performed with two continuum models, one based on the finite element analysis and another based on the multipole series expansion. This comparison validates the continuum models, shows their applicability limits, and provides reliable identification of the surface elastic constants.

Nanopores in Graphene and Other 2D Materials: A Decade's Journey toward Sequencing.

Nanopore techniques offer a low-cost, label-free, and high-throughput platform that could be used in single-molecule biosensing and in particular DNA sequencing. Since 2010, graphene and other two-dimensional (2D) materials have attracted considerable attention as membranes for producing nanopore devices, owing to their subnanometer thickness that can in theory provide the highest possible spatial resolution of detection. Moreover, 2D materials can be electrically conductive, which potentially enables alternative measurement schemes relying on the transverse current across the membrane material itself and thereby extends the technical capability of traditional ionic current-based nanopore devices. In this review, we discuss key advances in experimental and computational research into DNA sensing with nanopores built from 2D materials, focusing on both the ionic current and transverse current measurement schemes. Challenges associated with the development of 2D material nanopores toward DNA sequencing are further analyzed, concentrating on lowering the noise levels, slowing down DNA translocation, and inhibiting DNA fluctuations inside the pores. Finally, we overview future directions of research that may expedite the emergence of proof-of-concept DNA sequencing with 2D material nanopores.

Modular Assembly of Vibrationally and Electronically Coupled Rhenium Bipyridine Carbonyl Complexes on Silicon.

Hybrid inorganic/organic heterointerfaces are promising systems for next-generation photocatalytic, photovoltaic, and chemical-sensing applications. Their performance relies strongly on the development of robust and reliable surface passivation and functionalization protocols with (sub)molecular control. The structure, stability, and chemistry of the semiconductor surface determine the functionality of the hybrid assembly. Generally, these modification schemes have to be laboriously developed to satisfy the specific chemical demands of the semiconductor surface. The implementation of a chemically independent, yet highly selective, standardized surface functionalization scheme, compatible with nanoelectronic device fabrication, is of utmost technological relevance. Here, we introduce a modular surface assembly (MSA) approach that allows the covalent anchoring of molecular transition-metal complexes with sub-nanometer precision on any solid material by combining atomic layer deposition (ALD) and selectively self-assembled monolayers of phosphonic acids. ALD, as an essential tool in semiconductor device fabrication, is used to grow conformal aluminum oxide activation coatings, down to sub-nanometer thicknesses, on silicon surfaces to enable a selective step-by-step layer assembly of rhenium(I) bipyridine tricarbonyl molecular complexes. The modular surface assembly of molecular complexes generates precisely structured spatial ensembles with strong intermolecular vibrational and electronic coupling, as demonstrated by infrared spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy analysis. The structure of the MSA can be chosen to avoid electronic interactions with the semiconductor substrate to exclusively investigate the electronic interactions between the surface-immobilized molecular complexes.