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CoGe surface oxidation studied using X-ray photoelectron spectroscopy
摘要： Cobalt germanides have been widely studied as semiconductor contact materials, but recent theoretical studies suggest that they may also be excellent catalysts for methane steam reforming with stabilities and activities comparable to more expensive noble metal catalysts. We have sputter deposited CoGe alloy films and characterized their structure and morphology after post-deposition annealing in high vacuum up to 1000 °C. We used X-ray photoelectron spectroscopy to study the initial oxidation of amorphous and crystalline CoGe alloy surfaces under low pressures of O2 and H2O. The oxidation rate in O2 was found to be faster for an amorphous CoGe surface compared to a crystalline surface. We also found that there was little difference in the oxidation rate in H2O for either amorphous or crystalline surfaces. During O2 oxidation, the crystalline surface preferentially forms GeO and the amorphous surface preferentially forms GeO2. We have also observed preferential oxidation of Ge in the CoGe thin films. During temperature programmed desorption studies, we found that GeO desorption begins near 350 °C and that GeO2 decomposes to GeO and desorbs near 700 °C. More studies of CoGe catalysts are warranted, however GeO desorption may be a concern under reaction conditions when the film is subjected to an oxidizing environment.
关键词： Oxidation,Cobalt germanium,Temperature programmed desorption,Atomic force microscopy,X-ray photoelectron spectroscopy,X-ray diffraction
更新于2025-09-23 15:21:21
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Photoelectron Spectroscopy of Molecular Anion of Alq <sub/>3</sub> : An Estimation of Reorganization Energy for Electron Transport in the Bulk
摘要： A molecular anion of tris(8-hydroxyquinolinato)aluminum (Alq3) was generated by a pulsed discharge to the solid sample under supersonic expansion and its photoelectron spectrum was recorded after mass selection. The vertical detachment energy of Alq3? and the adiabatic electron affinity of Alq3 were determined to be 1.24 ± 0.01 and 0.89 ± 0.04 eV, respectively. By using these energies determined for monomeric Alq3, the reorganization energy for the intermolecular electron transport in bulk Alq3 was estimated to be 0.70 ± 0.08 eV.
关键词： Photoelectron Spectroscopy,Electron Transport,Reorganization Energy,Alq3,Molecular Anion
更新于2025-09-23 15:21:21
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Composition analysis of Ta <sub/>3</sub> N <sub/>5</sub> /W <sub/>18</sub> O <sub/>49</sub> nanocomposite through XPS
摘要： A characterization of a nanocomposite material consisting of Ta3N5 nanoparticles and W18O49 nanowires is presented. The material is of interest for photocatalytic applications, with a focus on pollution reduction through the photodegradation of dye waste; under white light illumination, the combination of Ta3N5 and W18O49 yielded an enhanced rate of dye degradation relative to Ta3N5 particles alone. The facile method of synthesis is thought to be a promising route for both upscale and commercial utilization of the material. X-ray photoelectron spectroscopy revealed a core–shell composite structure with W18O49 present as an overlayer on Ta3N5; the analyzed spectra for the C 1s, O 1s, Ta 4f, N 1s, W 4f, and Na 1s regions are reported. It should be noted that due to differential charging of the underlying Ta3N5 component relative to the W18O49 shell, an additional uncompensated voltage shift may exist in the Ta 4f and N 1s spectra.
关键词： x-ray photoelectron spectroscopy,XPS,dye degradation,W18O49,nanowires,composite,Ta3N5,photocatalysis
更新于2025-09-23 15:21:21
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Valence band behaviour of zirconium oxide, Photoelectron and Auger spectroscopy study
摘要： In this study X-ray Photoelectron Spectroscopy and Ultraviolet Photoelectron Spectroscopy were combined to investigate the effect of oxygen incorporation on the valence band behaviour of ZrOx. The Auger transitions involving valence bands are found to mimic the self-folded density of state measured using Ultraviolet Photoelectron Spectroscopy. The valence band once constructed in a sub-oxide form, stays at a fixed energy position despite the change in the stoichiometry. This behaviour is found to be useful in setting a reference for X-ray Photoelectron Spectroscopy charge correction. The results of the charged corrected spectra were compared to other methods and found to be in great agreement. Finally, a correlation between the core-level binding energy and the structural property of ZrOx is given.
关键词： valence band,Ultraviolet Photoelectron Spectroscopy,X-ray Photoelectron Spectroscopy,Photoelectron,zirconium oxide,Auger spectroscopy
更新于2025-09-23 15:21:01
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Slow photoelectron velocity-map imaging of cold C7? and C9?
摘要： High-resolution anion photoelectron spectra of cryogenically cooled C7? and C9? clusters obtained using slow photoelectron velocity-map imaging are presented, providing insight into the vibronic structure of neutral C7 and C9. These spectra yield accurate measurements of vibrational frequencies for the neutral clusters as well as electron affinities of 3.3517(4) and 3.6766(14) eV for C7 and C9, respectively. In the C7? spectrum, transitions involving the previously unreported v1 and v2 symmetric stretching modes, as well as the v9, v10, and v11 asymmetric bending modes, are assigned. Spin–orbit splitting is observed for several transitions in this spectrum, giving an energy difference of 28(6) cm?1 between the 2Π1/2g and 2Π3/2g spin–orbit levels of the C7? anion. In the spectrum of C9?, transitions involving the previously unreported symmetric stretch v1 and the asymmetric bend v11 are observed. In both spectra, several features are assigned to Franck-Condon forbidden transitions involving the doubly degenerate v10 and v11 modes of C7 and the v13 and v14 modes of C9. The appearance of these transitions is attributed to Herzberg-Teller coupling between the electronic states of the neutral clusters. Additional FC-forbidden transitions to states previously observed in gas-phase infrared experiments are observed and attributed to vibronic coupling between the electronic states of the anion, resulting in non-totally symmetric character in the anion’s full vibrational ground state. Finally, consideration of the energy dependence of detachment cross sections and Dyson orbital analyses reveal that addition of more carbon atoms to the linear chain results in photodetachment from delocalized molecular orbitals with increasing nodal structure, leading to threshold photodetachment cross sections that differ considerably from simple symmetry considerations.
关键词： Herzberg-Teller coupling,Franck-Condon forbidden transitions,anion photoelectron spectroscopy,vibronic structure,carbon clusters,slow photoelectron velocity-map imaging
更新于2025-09-23 15:21:01
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Structure determination of substrate influenced silicon nano-ribbon growth
摘要： Using photoelectron diffraction (XPD), photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED), we investigate the structure of silicon nano-ribbons grown on Au(1 1 0). We find that silicon forms two zigzag-terminated hexagonal chains along the [1 1 0]-substrate direction, while the gold substrate forms a bulk-typed surface reconstruction after silicon evaporation. Only two missing rows along the [1 1 0]-direction remain partially in their original structure at the Si/Au interface. Unlike silicon nano-ribbon formation on Ag(1 1 0), nano-ribbon growth on Au(1 1 0) is strongly substrate influenced by Van-der-Waals interaction and by AuSi bonding formation. This strong interaction leads to a substrate-driven hexagon formation, where the gold atoms are partially integrated into the ribbon structure. Besides the determination of the internal silicon nano-ribbon structure, we identify the origin of the two chemically shifted silicon components in the XPS spectra by deconvolving the diffraction pattern.
关键词： Photoelectron spectroscopy,Hexagonal chains,Nano-ribbon,Silicon,Photoelectron diffraction
更新于2025-09-23 15:21:01
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Effect of Ga introduction during the second stage of a coevaporation process of Cu(In,Ga)Se2 layers at low temperature on polyimide substrates
摘要： A proper control of Ga concentration pro?le is mandatory to achieve high e?ciency Cu(In,Ga)Se2 (CIGS) solar cells. At low temperature, deep gradients, detrimental for carriers' di?usion, are obtained when CIGS is deposited with a standard three-stage process: an optimization of the process is needed. In this study, we show the impact of a modify three-stage process on the depth of the notch by introducing Ga ?ux during the second stage from 0 nm/min to 1.1 nm/min. A higher open circuit voltage compensated by a lower short current density is obtained due to higher band gap energy. The surface and the bulk of the CIGS layer was analyzed at the end of the second stage by coupling di?erent characterization techniques: glow discharge optical emission spectroscopy, Raman and X-ray photoelectrons spectroscopy. The presence of binary compounds as well as a Ga enrichment at the end of the second stage are observed when Ga is introduced during the second stage.
关键词： low temperature,X-ray photoelectron spectroscopy,solar cells,Cu(In,Ga)Se2,three-stage process,glow discharge optical emission spectroscopy,Raman spectroscopy,CIGS,Ga concentration pro?le
更新于2025-09-23 15:21:01
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Application of Nanostructured Tungsten Fabricated by Helium Plasma Irradiation for Photoinduced Decolorization of Methylene Blue
摘要： The dendritic nanostructure was fabricated on a surface of tungsten plate by helium plasma irradiation. The nanostructure consisting of W metal was partially oxidized to form WO3 on exposure to air, and the resulting surface exhibited a broad photoabsorption in the range from 1 to 5 eV. We examined photoinduced reaction of methylene blue (MB) on the material. It was found that the partially and fully oxidized surface nanostructures were able to promote a decolorization of MB under photoirradiation even with the near-infrared light (< 1:55 eV), whose energy is lower than the band gap of WO3. The reaction rate was varied with the fraction of W and WO3 on the surface layers, that is, the partially oxidized sample promoted the reaction at a higher rate than the fully oxidized one. It is also found that the reaction rate decreased with time, which would be caused by the products accumulation on the surface and the surface oxidation.
关键词： Scanning electron microscopy (SEM),Tungsten oxide,Surface photochemistry,Plasma processing,Nano-wires, quantum wires, and nanotubes,Visible/ultraviolet absorption spectroscopy, X-ray photoelectron spectroscopy
更新于2025-09-23 15:21:01
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Enhancement in the performance of nanostructured CuOa??ZnO solar cells by band alignment
摘要： In this study, we investigated the effect of cobalt doping on band alignment and the performance of nanostructured ZnO/CuO heterojunction solar cells. ZnO nanorods and CuO nanostructures were fabricated by a low-temperature and cost-effective chemical bath deposition technique. The band offsets between Zn1?xCoxO (x = 0, 0.05, 0.10, 0.15, and 0.20) and CuO nanostructures were estimated using X-ray photoelectron spectroscopy and it was observed that the reduction of the conduction band offset with CuO. This also results in an enhancement in the open-circuit voltage. It was demonstrated that an optimal amount of cobalt doping could effectively passivate the ZnO related defects, resulting in a suitable conduction band offset, suppressing interface recombination, and enhancing conductivity and mobility. The capacitance–voltage analysis demonstrated the effectiveness of cobalt doping on enhancing the depletion width and built-in potential. Through impedance spectroscopy analysis, it was shown that recombination resistance increased up to 10% cobalt doping, thus decreased charge recombination at the interface. Further, it was demonstrated that the insertion of a thin layer of molybdenum oxide (MoO3) between the active layer (CuO) and the gold electrode hinders the formation of a Schottky junction and improved charge extraction at the interface. The ZnO/CuO solar cells with 10% cobalt doped ZnO and 20 nm thick MoO3 buffer layer achieved the best power conversion efficiency of 2.11%. Our results demonstrate the crucial role of the band alignment on the performance of the ZnO/CuO heterojunction solar cells and could pave the way for further progress on improving conversion efficiency in oxide-based heterojunction solar cells.
关键词： nanostructured,solar cells,X-ray photoelectron spectroscopy,power conversion efficiency,molybdenum oxide,chemical bath deposition,band alignment,CuO–ZnO,cobalt doping
更新于2025-09-23 15:21:01
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Low temperature platinum chemical vapor deposition on functionalized self-assembled monolayers
摘要： The reaction pathways of Pt CVD using (COD)PtMe2 – xClx (x = 0, 1, 2) have been investigated on functionalized self-assembled monolayers (SAMs) as models for organic substrates. Residual gas analysis for (COD)PtMe2 and (COD)PtMeCl is consistent with the loss of methyl radicals as the initial step in deposition, while for (COD)PtCl2, the first step is the loss of a chlorine radical. It is further shown using x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry that the deposition process leads to chemical damage of the SAM layer and little Pt deposition. Using this understanding, it is demonstrated that the Pt CVD rate can be controlled using a radical trap. In the presence of 1,4-cyclohexadiene, a well-known alkyl radical trap, Pt deposition was increased by 5× to 10×, creating a room-temperature effective Pt CVD process.
关键词： time-of-flight secondary ion mass spectrometry,x-ray photoelectron spectroscopy,Pt CVD,chemical vapor deposition,self-assembled monolayers,radical trap
更新于2025-09-23 15:21:01