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Solvent influence on the surface morphology of P3HT thin films revealed by photoemission electron microscopy
摘要： Only rigorous understanding of the relationship between the nano-scale morphology of organic thin films and the performance of the devices built from them will ultimately lead to design rules that can guide a structured development on the field of organic electronics. Despite great effort, unraveling the nanoscale structure of the films is still a challenge in itself. Here we demonstrate that photoemission electron microscopy can provide valuable insights into the chain orientation, domains size and grain boundary characteristics of P3HT films spun cast from different solvents at room as well as at elevated temperatures.
关键词： surface morphology,photoemission electron microscopy,organic electronics,solvent influence,P3HT
更新于2025-09-11 14:15:04
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Present status of photoemission electron microscope newly installed in SPring-8 for time-resolved nanospectroscopy
摘要： A photoemission electron microscope (PEEM) system has been newly installed at the soft X-ray undulator beamline (BL17SU) of SPring-8 to realize time-resolved nanospectroscopy for the local transient electronic structures of advanced materials. This PEEM is a versatile machine composed of an electrostatic lens system and is intended for use in specific experiments such as time-resolved measurements. Pump–probe measurements in tandem with a femtosecond pulsed-laser system and an X-ray chopper are now readily available.
关键词： photoemission electron microscope,time-resolved nanospectroscopy,SPring-8,soft X-ray undulator beamline,PEEM
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Airy Plasmon Pulses Investigated by Multiphoton Photoemission Electron Microscopy (PEEM)
摘要： Airy wave packets are a special class of non-diffractive solutions to the wave equation which accelerate along a bend trajectory. Their self-healing property makes them particularly interesting for integrated nanophotonic applications. Surface plasmon polaritons (SPPs), in contrast, have the beneficial property to be bound to the two-dimensional surface of a noble metal and enable sub-wavelength confinement. In two dimensions, Airy wave packets are the only non-diffracting solution of the wave equation. The high intrinsic bandwidth of a plasmonic excitation makes it ideal for ultrafast photonics. Photoemission Electron Microscopy (PEEM) represents an ideal tool to deliver images of these processes. The method has been successfully applied by us in the past to investigate the transient behavior of an optical nanoantenna emitting Hankel plasmon pulses. We have used PEEM in combination with a variable wavelength excitation from an optical parametric chirped pulse amplifier system (OPCPA) to experimentally investigate Airy plasmon pulses emitted by an excitation grating. The OPCPA system allows us to experimentally investigate the performance of the excitation in the wavelength range between 670 and 840 nm, where a 3-photon-process is necessary to emit an electron. In this way, we can sample the spectral response which is necessary to determine the ultrafast characteristics of the Airy plasmon pulse. We find that the excitation of stationary Airy plasmons is possible over a large bandwidth. However, the creation of an ultrafast hotspot requires also a matching of the spectral phase which is hard to fulfill in strong dispersing systems. We therefore accompany our measurements with rigorous finite-difference time domain simulations, a suitable nonlinear electron yield model, and analytic calculations to determine the modal purity of the Airy plasmon excitation based on reciprocity. Results support our experimental data and suggest that further improvements of the excitation scheme are necessary to obtain spatio-temporal hotspots.
关键词： PEEM,Surface plasmon polaritons,SPPs,ultrafast photonics,Multiphoton Photoemission Electron Microscopy,Airy plasmon pulses
更新于2025-09-11 14:15:04
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Beyond the molecular movie: Dynamics of bands and bonds during a photoinduced phase transition
摘要： Ultrafast nonequilibrium dynamics offer a route to study the microscopic interactions that govern macroscopic behavior. In particular, photoinduced phase transitions (PIPTs) in solids provide a test case for how forces, and the resulting atomic motion along a reaction coordinate, originate from a nonequilibrium population of excited electronic states. Using femtosecond photoemission, we obtain access to the transient electronic structure during an ultrafast PIPT in a model system: indium nanowires on a silicon(111) surface. We uncover a detailed reaction pathway, allowing a direct comparison with the dynamics predicted by ab initio simulations. This further reveals the crucial role played by localized photoholes in shaping the potential energy landscape and enables a combined momentum- and real-space description of PIPTs, including the ultrafast formation of chemical bonds.
关键词： Silicon surface,Photoinduced phase transitions,Chemical bonds,Electronic structure,Indium nanowires,Femtosecond photoemission,Ultrafast dynamics
更新于2025-09-10 09:29:36
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || Synchrotron-based Spectroscopy In On-Surface Polymerization of Covalent Networks
摘要： Synchrotron radiation is a powerful tool to probe physical properties of materials on the nanoscopic scale. It can provide a chemical fingerprint of a nanomaterial with unrivalled resolution, it can measure the geometric structure down to thousands of a nanometer with not only elemental sensitivity but also chemical sensitivity, and it can study charge transfer dynamics in the sub-nanosecond regime. Within this article the application of synchrotron radiation to studying on-surface catalysis, to the view of forming two-dimensional covalent networks, will be explored.
关键词： covalent networks,on-surface polymerization,Normal Incidence X-ray Standing Waves,Synchrotron radiation,X-ray Photoemission Spectroscopy,Near Edge X-ray Absorption Fine Structure
更新于2025-09-10 09:29:36
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In-Plane Optical Anisotropy of Low-Symmetry 2D GeSe
摘要： As a new member of 2D materials, GeSe has attracted considerable attention recently due to its fascinating in-plane anisotropic vibrational, electrical, and optical properties originating from the low-symmetry crystal structure. Among these anisotropic properties, the anisotropic optical property, as a new degree of freedom to manipulate optoelectronic properties in 2D materials, is of great importance for practical applications. However, the fundamental understanding of the optical anisotropy of GeSe is still under exploration, severely restricting its utility in polarization-sensitive optical systems. Here, a systematic study about the in-plane optical anisotropy of GeSe is reported, including its anisotropic optical absorption, reflection, extinction, and refraction. The anisotropic band structure of GeSe is experimentally observed for the first time through angle-resolved photoemission spectroscopy, explaining the origin of the optical anisotropy. The anisotropic reflection and refraction of GeSe are further directly visualized through the angle-dependent optical contrast of GeSe flakes by azimuth-dependent reflectance difference microscopy and polarization-resolved optical microscopy, respectively. Finally, GeSe-based photodetectors exhibit a polarization-sensitive photoresponsivity due to the intrinsic linear dichroism. This study provides fundamental information for the optical anisotropy of GeSe, forcefully stimulating the exploration of novel GeSe-based optical and optoelectronic applications.
关键词： polarization-resolved optical microscopy,azimuth-dependent reflectance difference microscopy,birefringence,angle-resolved photoemission spectroscopy,germanium monoselenide
更新于2025-09-10 09:29:36
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Oxidation of Epitaxial Silicene on Ag(111)
摘要： The high chemical reactivity of epitaxial silicene on Ag(111) still remains a debated subject in the literature. In particular results on the oxidation of epitaxial silicene and its related lifetime under ambient conditions are controversially discussed. Here, a detailed investigation of the oxygen exposure to epitaxial silicene layers investigated by means of X-ray photoemission and in situ Raman spectroscopy is reported. The results should clearly cease the discussion on the stability of epitaxial silicene against oxygen as it becomes completely oxidized after an exposure to only 100 L of oxygen. Such a small dose sets strict limits for ex situ studies of epitaxial silicene. Besides the formation of silicon oxide also the silver substrate surface oxidizes, suggesting that the silicene layer can hardly protect it, probably owing to the high number of domain boundaries within the silicene layer.
关键词： epitaxial silicene,2D materials,oxidation,in situ Raman spectroscopy,photoemission spectroscopy
更新于2025-09-10 09:29:36
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European Microscopy Congress 2016: Proceedings || Is the electronic structure of few layer transition metal dichalcogenides always two dimensional ?
摘要： The electronic structure of the transition metal dichalcogenides (TMDs) is investigated using angle-resolved photoemission spectroscopy (ARPES). We observe a new class of layered materials that can be prepared in various thicknesses down to single layers. Compared with the more well-known graphene, the TMDs are semiconductors and can be more useful in applications where an energy gap is essential. Our results show that the electronic structure of the TMDs is highly dependent on the number of layers, with a transition from indirect to direct bandgap as the thickness is reduced to a single layer. This transition is accompanied by a significant enhancement in photoluminescence intensity, making monolayer TMDs promising candidates for optoelectronic applications.
关键词： Angle-resolved photoemission spectroscopy,Bandgap engineering,Electronic structure,Optoelectronic applications,Transition metal dichalcogenides
更新于2025-09-10 09:29:36
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Impact of MoS2 Layer Transfer on Electrostatics of MoS2/SiO2 Interface
摘要： Using internal photoemission of electrons from few-monolayer thin MoS2 films into SiO2 we found that the MoS2 layer transfer processing perturbs electroneutrality of the interface, leading to an increase of the electron barrier height by ≈0.5-1 eV as compared to the case of the same films synthesized directly on SiO2. This effect is associated with the formation of an interface dipole, tentatively ascribed to interaction of H2O molecules with the SiO2 surface resulting in the incorporation of silanol (SiOH) groups. This violation of the interface electroneutrality may account for additional electron scattering in ultra-thin transferred films and threshold voltage instabilities. Post-transfer annealing in H2S is shown to reduce the transfer-induced interface degradation.
关键词： Layer transfer,internal photoemission,interface barrier,2-dimensional materials
更新于2025-09-10 09:29:36
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surface alloy
摘要： We have investigated the atomic and electronic structure of the (√3×√3)R30? SnAu2/Au(111) surface alloy. Low-energy electron diffraction and scanning tunneling microscopy measurements show that the native herringbone reconstruction of bare Au(111) surface remains intact after formation of a long-range ordered (√3×√3)R30? SnAu2/Au(111) surface alloy. Angle-resolved photoemission and two-photon photoemission spectroscopy techniques reveal Rashba-type spin-split bands in the occupied valence band with comparable momentum space splitting as observed for the Au(111) surface state, but with a hole-like parabolic dispersion. Our experimental findings are compared with density functional theory (DFT) calculation that fully support our experimental findings. Taking advantage of the good agreement between our DFT calculations and the experimental results, we are able to extract that the occupied Sn-Au hybrid band is of (s, d )-orbital character, while the unoccupied Sn-Au hybrid bands are of (p, d )-orbital character. Hence we can conclude that the Rashba-type spin splitting of the hole-like Sn-Au hybrid surface state is caused by the significant mixing of Au d with Sn s states in conjunction with the strong atomic spin-orbit coupling of Au, i.e., of the substrate.
关键词： angle-resolved photoemission spectroscopy,density functional theory,SnAu2/Au(111) surface alloy,Rashba-type spin splitting,two-photon photoemission spectroscopy
更新于2025-09-09 09:28:46