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Trimer bonding states on the surface of the transition-metal dichalcogenide
摘要： We report a comprehensive study on the surface structural and electronic properties of TaTe2 at room temperature. The surface structure was investigated using both low energy electron diffraction intensity versus voltage and density functional theory calculations. The relaxed structures obtained from the two methods are in good agreement, which is very similar to the bulk, maintaining double zigzag trimer chains. The calculated density of states indicates that such structure originates from the trimer bonding states of the Ta dxz and dxy orbitals. This work will further provide new insights towards the understanding of the charge density wave phase transition in TaTe2 at low temperature.
关键词： surface structure,low energy electron diffraction,density functional theory,charge density wave,TaTe2
更新于2025-09-10 09:29:36
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The Origin of the π-π Spacing Change upon Doping of Semiconducting Polymers
摘要： While there is agreement about the local structural order of semiconducting polymers such as poly(3-hexylthiophene) (P3HT), there is still debate over the impact of molecular doping. One prevalent interpretation is that dopant molecules intercalate in the π-π stacking of crystallites; however, this idea has recently been challenged. We present here electron diffraction measurements of P3HT doped with the two dopants 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) and molybdenum tris[1-(methoxycarbonyl)-2-(trifluoromethyl)-ethane-1,2-dithiolene] (Mo(tfd-CO2Me)3), which have considerably different sizes and shapes, processed by different doping techniques. We observe a reduction in the π-π spacing of P3HT upon doping with both dopant molecules and doping techniques. These data are not consistent with both of the dopants intercalating in the π-π stacks and an alternative explanation is, therefore, required to explain these results. Density functional theory calculations for P3HT model oligomers suggest that the polaron delocalizes between adjacent chains and thus leads to attractive forces that reduce the π-π spacing, without the physical presence of any dopant molecules. Our study emphasizes that not only geometric effects induced by dopant molecules lead to the observed reduction of π-π spacing, but the charging itself.
关键词： semiconducting polymers,electron diffraction,π-π spacing,F4TCNQ,Mo(tfd-CO2Me)3,density functional theory,molecular doping,P3HT
更新于2025-09-10 09:29:36
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Surface structures of tellurium on Si(111)–(7?×?7) studied by low-energy electron diffraction and scanning tunneling microscopy
摘要： The Te-covered Si(111) surface has received recent interest as a template for the epitaxy of van der Waals (vdW) materials, e.g. Bi2Te3. Here, we report the formation of a Te buffer layer on Si(111)–(7×7) by low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). While deposition of several monolayer (ML) of Te on the Si(111)–(7×7) surface at room temperature results in an amorphous Te layer, increasing the substrate temperature to 770 K results in a weak (7×7) electron diffraction pattern. Scanning tunneling microscopy of this surface shows remaining corner holes from the Si(111)–(7×7) surface reconstruction and clusters in the faulted and unfaulted halves of the (7×7) unit cells. Increasing the substrate temperature further to 920 K leads to a Te/Si(111)–(2√3×2√3)R30° surface reconstruction. We find that this surface configuration has an atomically flat structure with threefold symmetry.
关键词： scanning tunneling microscopy,surface reconstruction,Si(111),tellurium,low-energy electron diffraction
更新于2025-09-10 09:29:36
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Bohmian trajectory-bloch wave approach to dynamical simulation of electron diffraction in crystal
摘要： The Bohmian trajectory method is employed to study electron diffraction in crystalline materials. It provides a fresh understanding of the process of electron diffraction, including traveling channels of electrons and formation of diffraction patterns. By combining it with the Bloch wave method, the electron trajectories can be calculated more efficiently than the traditional wave-packet propagation algorithm. Meanwhile, we propose a momentum expectation approach which is a good approximation method with even higher computational efficiency. Both methods result in intuitive and accurate electron trajectories for the simulation of the electron backscatter diffraction (EBSD) pattern. Excellent agreement has been obtained between the simulated trajectory distributions and the experimental EBSD pattern from Mo (001) at 20 kV, where the Kikuchi patterns and higher order Laue zone rings are characterized.
关键词： quantum trajectories,electron diffraction,quantum simulation,Bohmian mechanics
更新于2025-09-09 09:28:46
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Nanometer-scale local structural study of the paraelectric cubic phase of KNbO <sub/>3</sub> by convergent-beam electron diffraction
摘要： Nanometer-scale local structures of the paraelectric cubic phase of potassium niobate (KNbO3) are examined by convergent-beam electron diffraction (CBED) using a nanometer-size electron probe. The breaking of the cubic symmetry has been directly observed in the nanometer-scale areas of the cubic phase of KNbO3. This indicates the existence of local polarization clusters in the cubic phase. Symmetry breaking index maps for the fourfold rotation symmetry are given at different temperatures with the combined use of scanning transmission electron microscopy (STEM) and CBED (STEM–CBED). ? 2017 The Japan Society of Applied Physics
关键词： local polarization clusters,CBED,convergent-beam electron diffraction,STEM,KNbO3,symmetry breaking
更新于2025-09-09 09:28:46
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Is There Chiral Correlation between Graphitic Layers in Double-Wall Carbon Nanotubes?
摘要： Because of the unique concentric structure, double-wall carbon nanotubes (DWNTs) possess fascinating properties which depend on the respective chirality of both the outer and the inner tubes. In this work, we study the chiral correlations of DWNTs synthesized by chemical vapor deposition on Fe nanoparticles. Contrary to some recent report, the distribution of chiral angle difference between inner and outer tubes in our work agrees with that calculated for all possible configurations. Remarkably, DWNTs with commensurate structures, i.e. outer and inner tubes have same chiral angles, are observed. The mechanism for the formation of DWNTs with approximately commensurate structures is discussed on the basis of layer by layer model. Furthermore, the interactional energies between the inner and outer walls are calculated to address the stability of different DWNT configurations. This work helps understand the growth mechanism of DWNTs and comprehend their structure stabilities with different configurations.
关键词： chiral angle difference,electron diffraction,structure correlation,double-wall carbon nanotube
更新于2025-09-09 09:28:46
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[IEEE 2018 7th Electronic System-Integration Technology Conference (ESTC) - Dresden, Germany (2018.9.18-2018.9.21)] 2018 7th Electronic System-Integration Technology Conference (ESTC) - Ultrafast miniaturized pulsed electron gun for timeresolved surface measurements
摘要： We report the development of an ultrafast miniaturized pulsed electron gun for the implementation of time-resolved low-energy electron diffraction. This electron gun consists of a nanotip photocathode and an einzel lens for beam collimation. Assembly and electrical contacting of the gun is achieved in a multistep process involving photolithography and focused-ion-beam etching. First applications in a backscattering geometry were demonstrated with a temporal resolution of 1 ps at an electron energy of 80 eV.
关键词： Low energy electron diffraction,charge-density wave,time resolved
更新于2025-09-09 09:28:46
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Growth and surface structural study of tin oxide films on Ag(001)
摘要： Tin oxide was prepared by reactive deposition of Sn in an O2 atmosphere at both room temperature (RT) and high temperature (HT) at 573 K as well from one monolayer to ten monolayer film coverages. The grown films were studied at RT by a combination of x-ray photoemission spectroscopy (XPS), low energy electron diffraction (LEED) and ultraviolet photoemission spectroscopy (UPS). At RT, the coexistence of both SnO and SnO2 was confirmed by XPS and valence band data with more SnO being formed at higher coverage. However, only one oxidised phase of tin oxide mainly due to SnO2 was formed at HT for most of the coverage. Presence of SnO was also confirmed only at the highest coverage studied here for HT. A multidomain LEED pattern having square (1 × 1) domains at 30° to each other was reported for low coverage of tin oxide at RT, which with an increase in coverage, gives rise to diffused background confirming no ordered tin oxide was formed. The similar multi-domain structure was also noticed for HT growth from lower coverage up to 5 monolayer equivalent (MLE) coverage which then transformed into hexagonal multidomain LEED pattern for higher coverage confirming the presence of clear oxide phase, unlike the RT growth case.
关键词： Thin films,Low energy electron diffraction,Photoemission spectroscopy
更新于2025-09-04 15:30:14
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The Double Slit Experiment-Explained
摘要： The wavelet envisioned by Huygen’s in diffraction phenomenon is re-interpreted as being polarized after passing through slit/hole which removed the electric field component from the Electromagnetic Radiation (EM-R), the remained wave consist of the Circular Magnetic Field (CMF), this CMF lost the speed of light and the electric field, hence it’s a short distance travel field, originated from the CMF produced by accelerated electrons, integrated with the Electric Field (EF) during the Flip-Flop (F-F) mechanism producing EM-R; hence the passing of light through a single hole/slit resulted in a CMF which reproduced as rings on the monitor screen in single wave diffraction, while the interference of two such CMF in double slits experiment, produced constructive or destructive interference forming patches on the monitor screen; and the perceived electron diffraction is an enter of two CMF from a single electron into a slit then emerged to produce constructive or destructive interference, in addition to the electron which entered and emerged from the slit with the stronger CMF, the paper finally derived the origin of Planck ‘constant (h) for the second time; the logical interpretation of double slits diffraction will restore the common sense in the physical world, distorted by the pilot wave.
关键词： Electron diffraction,wavelet,Circular magnetic field,Double slit experiment,Polarization,Origin of Planck’ constant
更新于2025-09-04 15:30:14