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Mechanism of field-induced manipulation of Cu-phthalocyanines on a Bi surface using scanning tunneling microscope
摘要： We have revisited our hypothesis [K. Nagaoka et al., Jpn. J. Appl. Phys. 57 (2018) 020301] regarding the control of the motion and assembly of copper phthalocyanine (CuPc) molecules on a Bi(001) surface using a scanning tunneling microscope (STM) tip. The proposal that the observed diffusion and condensation are not due to the adsorption/desorption of molecules via the tip by applying a bias voltage was investigated for field-induced manipulation. Our experiments show that CuPc cannot move across steps or condense on different terraces on the Bi(001) surface. When confined to a nano-scale region, the CuPc molecules assemble into ordered single-layer islands. The island position can be manipulated using the STM tip, with an almost constant number of condensed molecules remaining inside the terrace. These results allowed us to rule out the possibility of picking-up and depositing molecules by the STM tip.
关键词： STM,phthalocyanine,self-assembly,field-induced manipulation,bismuth,surface science
更新于2025-09-23 15:23:52
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Surface/edge functionalized boron nitride quantum dots: Spectroscopic fingerprint of bandgap modification by chemical functionalization
摘要： Promising properties of boron nitride nanomaterials such as their chemical, thermal, and mechanical stability have made them suitable materials in a various range of applications. However, their low electrical conductivity and wide bandgap, particularly in the case of boron nitride quantum dots (BNQDs), have given rise to severe limitations. Efforts on bandgap engineering through doping and surface functionalization have gained little success due to their high thermodynamic stability and inertness. Herein, we present a novel approach to functionalize BNQDs by hydroxyl, methyl, and amine functional groups aiming to adjust the electronic structure. The successful exfoliation is demonstrated by transmission electron microscopy, and surface functionalization is elaborated by FTIR and XPS. Modifications of the electronic and optical properties are shown by UV–Vis and PL measurements. The formation of two absorption edges in bandgaps of BNQDs due to the delocalizing of the Px and Pz orbitals as result of edge/surface passivating groups is demonstrated. Splitting of the main transition bandgap of bulk BN from 5.9 eV to two absorption edges for hydroxyl (2.3-3.6 eV), methyl (3.2-4.2 eV), and amine (3.1-4 eV) is shown. These findings offer a bandgap engineering approach for BNQDs, which can boost their applications in quantum emitters (nanophotonics) and photovoltaic devices.
关键词： Surface science,Nanoparticle semiconductor,Quantum confinement,Bandgap engineering
更新于2025-09-12 10:27:22
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || 2D Ternary Oxide Layers: New Paradigms of Structure and Stoichiometry
摘要： Two-dimensional (2D) oxide materials have tremendous potential in fundamental research and cutting edge technologies owing to their outstanding physical and chemical properties, which makes them excellent candidates for a wide range of applications including power harvesting, hydrogen storage, fuel cells, gas sensors, advanced electronic and spintronic devices, and nanocatalysis.1,2 To gain a fundamental understanding of the novel properties, afforded by the reduced dimension of oxide nanostructures, structurally well-defined model systems have been utilized, typically in the form of ultrathin oxide films (with a thickness of one to few atomic layers) epitaxially grown on single-crystal metal surfaces. Emergent phenomena in their geometric architecture, electronic and vibrational structure, chemical nature and magnetic behavior have been recognized,3–8 rendering oxide nanolayers vast and unforeseen opportunities in science and technology. To date, most of the studies have been focused on binary 2D oxides, but the increased interest in more complex oxide materials, such as ternary or multicomponent oxides with a broader range of functionalities, requires an adequate understanding of their properties at the nanoscale, which is still scarce. Even for high technologically important ternary oxides, such as the perovskites, there are only few studies reporting on the preparation of 2D oxide layers on metal supports, which are found to display unique structural behavior with no counterpart in the bulk.9,10 One reason for this is that the preparation of ternary oxide nanolayers with well-defined structure and stoichiometry is more challenging than for binary oxides, which requires the development of new fabrication strategies, where suitable thermodynamic and kinetic parameters have to be optimized in a narrow multiparameter space to obtain structures with desired stoichiometry and 2D morphology. Moreover, the elucidation of their structural properties at the atomic level is experimentally and theoretically more demanding than for the binary oxides.
关键词： stoichiometry,surface science techniques,2D ternary oxide layers,structure,metal tungstates
更新于2025-09-10 09:29:36
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Stark effect or coverage dependence? Disentangling the EC-SEIRAS vibrational shift of sulfate on Au(111)
摘要： Infrared spectroscopy is a widely employed analytical tool in (electrochemical) surface science as the spectra contain a wealth of information about the interaction of interfacial adsorbates with their environment. Separating and quantifying individual contributions, for example, of co-adsorbates, the substrate or electric field effects, on the overall spectral response, however, is often non-trivial as the various interactions manifest themselves in similar spectral behavior. Here, we present an experimental approach to differentiate between and quantify potential-induced coverage dependence and field-related Stark effects observed in a sulfate band shift of 93.5 ± 1.5 cm?1/V in electrochemical infrared spectra of the showcase sulfate/Au(111) interface. In combination with a simple linear model equation used to describe the potential-induced peak shift of the sulfate stretch vibration, we determine the coverage dependence contribution to be 15.6 ± 1.2 cm?1/θSO and the Stark effect to amount to 75.6 ± 2.7 cm?1/V. Our work provides a novel route to gain fundamental insight into interfacial adsorbate interactions in electrochemical surface science.
关键词： Stark effect,Infrared spectroscopy,sulfate/Au(111) interface,electrochemical surface science,coverage dependence
更新于2025-09-09 09:28:46