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Detailed investigation of photoluminescence, structural, and elemental properties of ZnO thin films under various annealing ambient
摘要： Zinc oxide (ZnO) has extensively exploited the material in the field of optoelectronics due to its inherent wide bandgap and high electron mobility. Properties of ZnO is very sensitive to its deposition methods and conditions. We report the effect of annealing ambient (i.e. argon, nitrogen, oxygen, or vacuum) on the optical, structural and elemental properties of the RF-sputtered ZnO thin films. In this work, we have performed compressive study on the effects of annealing ambient on a donor-bound exciton peak, exciton-exciton and electron-exciton scattering using low temperature (18 K) photoluminescence measurement which is not yet well understood. We have reported dominant on the donor-bound exciton peak with the lowest full width half maximum value (~4.48 nm) for annealing in an oxygen ambient. The annealing ambient strongly influenced the elemental properties of the film and we have reported the reduction in oxygen vacancy with annealing in an oxygen ambient. This work showed that the influence of ex-situ annealing ambient on exciton emission of ZnO thin films and thus providing a tool for enhancing the optical and elemental properties of the film.
关键词： ZnO thin films,Radio-frequency sputtering,X-ray photoelectron spectroscopy,Rapid thermal processing,Photoluminescence
更新于2025-09-23 15:19:57
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Reconstruction of attosecond pulses in the presence of interfering dressing fields using a 100 kHz laser system at ELI-ALPS
摘要： Attosecond Pulse Trains (APT) generated by high-harmonic generation (HHG) of high-intensity near-infrared (IR) laser pulses have proven valuable for studying the electronic dynamics of atomic and molecular species. However, the high intensities required for high-photon-energy, high-flux HHG usually limit the class of adequate laser systems to repetition rates below 10 kHz. Here, APT’s generated from the 100 kHz, 160 W, 40 fs laser system (HR-1) currently under commissioning at the Extreme Light Infrastructure Attosecond Light Pulse Source (ELI-ALPS) are reconstructed using the Reconstruction of Attosecond Beating By Interference of two-photon Transitions (RABBIT) technique. These experiments constitute the first attosecond time-resolved photoelectron spectroscopy measurements with attosecond pulses performed at 100 kHz repetition rate and one of the first experiments performed at ELI-ALPS in the framework of projects commissioning its newly installed technologies. These RABBIT measurements were taken with an additional IR field temporally locked to the extreme-ultraviolet APT, resulting in an atypical ω beating. We show that the phase of the 2ω beating recorded under these conditions is strictly identical to that observed in standard RABBIT measurements within second-order perturbation theory. This work highlights an experimental simplification for future experiments based on attosecond interferometry (or RABBIT), which is particularly useful when lasers with high average powers are used.
关键词： photoelectron spectroscopy,High-harmonic generation,attosecond,RABBIT
更新于2025-09-23 15:19:57
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Deeply cooled and temperature controlled microjets: Liquid ammonia solutions released into vacuum for analysis by photoelectron spectroscopy
摘要： A versatile, temperature controlled apparatus is presented, which generates deeply cooled liquid microjets of condensed gases, expelling them via a small aperture into vacuum for use in photoelectron spectroscopy (PES). The functionality of the design is demonstrated by temperature- and concentration-dependent PES measurements of liquid ammonia and solutions of KI and NH4I in liquid ammonia. The experimental setup is not limited to the usage of liquid ammonia solutions solely.
关键词： NH4I,KI,liquid microjets,liquid ammonia,temperature control,photoelectron spectroscopy
更新于2025-09-23 15:19:57
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Scanning atmospheric-pressure plasma jet treatment of nickel oxide with peak temperature of a??500 ?°C for fabricating pa??ia??n structure perovskite solar cells
摘要： Scanning atmospheric-pressure plasma jet (APPJ) treatment of nickel oxide with a peak temperature of 500 °C was performed for fabricating p–i–n structure perovskite solar cells (PSCs). APPJ post-treatment leading to enhanced light scattering in PSCs that in turn increases the haze of NiO on FTO glass, improves the cell efficiency. APPJ treatment on NiO also improves the wettability to facilitate the follow-up deposition of CH3NH3PbI3. This also leads to better PSC performance. X-ray photoelectron spectroscopy indicates that APPJ treatment results in fewer C–N bonds and reduced NiAc2 content, suggesting more complete conversion of the liquid precursor into NiO. With three APPJ scans, the average PCE improves from 11.91% to 13.47%, with the best-performing PSC achieving an efficiency of 15.67%.
关键词： X-ray photoelectron spectroscopy,light scattering,Scanning atmospheric-pressure plasma jet,perovskite solar cells,wettability,nickel oxide
更新于2025-09-23 15:19:57
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Hybrid chemical bath deposition-CdS/sputter-Zn(O,S) alternative buffer for Cu <sub/>2</sub> ZnSn(S,Se) <sub/>4</sub> based solar cells
摘要： To replace the conventionally used CdS buffers in Cu2ZnSn(S,Se)4 (CZTSSe) based thin-film solar cells, sputtered Zn(O,S) buffer layers have been investigated. Zn(O,S) layers with three different [O]/([O] + [S]) ratios (0.4, 0.7, and 0.8)—and a combination of Zn(O,S) and CdS (“hybrid buffer layer”) were studied. In comparison to the CdS reference, the external quantum efficiency (EQE) of the Zn(O,S)-buffered devices increases in the short- and long-wavelength regions of the spectrum. However, the average EQE ranges below that of the CdS reference, and the devices show a low open-circuit voltage (VOC). By adding a very thin CdS layer (5 nm) between the absorber and the Zn(O,S) buffer, the VOC loss is completely avoided. Using thicker intermediate CdS layers result in a further device improvement, with VOC values above those of the CdS reference. X-ray photoelectron spectroscopy (XPS) measurements suggest that the thin CdS layer prevents damage to the absorber surface during the sputter deposition of the Zn(O,S) buffer. With the hybrid buffer configuration, a record VOC deficit, i.e., a minimum difference between bandgap energy Eg (divided by the elementary charge q) and VOC (Eg/q – VOC) of 519 mV could be obtained, i.e., the lowest value reported for kesterite solar cells to date. Thus, the hybrid buffer configuration is a promising approach to overcome one of the main bottlenecks of kesterite-based solar cells, while simultaneously also reducing the amount of cadmium needed in the device.
关键词： VOC deficit,Cu2ZnSn(S,Se)4,CdS,hybrid buffer layer,open-circuit voltage,X-ray photoelectron spectroscopy,thin-film solar cells,Zn(O,S) buffer layers,external quantum efficiency
更新于2025-09-23 15:19:57
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Growth of Ag(1?1?1) on Si(1?1?1) with nearly flat band and abrupt interface
摘要： Growth of Ag films of up to 30 nm thickness on Si(1 1 1) 7 × 7 at room temperature is investigated by low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). LEED revealed the coexistence of Ag and Si spots starting with 1 monolayer (ML) of Ag deposited. The Ag lattice constant, starting with 25 ML, is slightly higher than for bulk Ag and increase linearly with Ag thickness, reaching about 4.2 nm for the thickest films. The average terrace widths detected from LEED spot profile analysis are about 30 nm for clean Si(1 1 1) 7 × 7 and about 5.5 nm for the thickest Ag(1 1 1) film, in agreement with STM observations. The intensity variation of core levels analyzed by XPS is taken into account by a model assuming the initial formation of Ag islands with linear variation of coverage vs. the amount of Ag deposited, followed by growth in a quasi layer-by-layer mode. The interface barrier is in the range of 0.4 eV, lower than all values reported previously. Ag deposited on Si(1 1 1) 7 × 7 at room temperature provides flat Ag(1 1 1) for synthesis of 2D materials, and may be used for low barrier Schottky diodes.
关键词： Scanning tunneling microscopy,Low energy electron diffraction,X-ray photoelectron spectroscopy,Ag/Si(1 1 1),Molecular beam epitaxy,Surface barrier height
更新于2025-09-23 15:19:57
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Mechanical stress dependence of the Fermi level pinning on an oxidized silicon surface
摘要： A combination of micro-Raman spectroscopy and micro-XPS (X-ray photo-electron spectroscopy) mapping on statically deflected p-type silicon cantilevers is used to study the mechanical stress dependence of the Fermi level pinning at an oxidized silicon (001) surface. With uniaxial compressive and tensile stress applied parallel to the ?110? crystal direction, the observations are relevant to the electronic properties of strain-silicon nano-devices with large surface-to-volume ratios such as nanowires and nanomembranes. The surface Fermi level pinning is found to be even in applied stress, a fact that may be related to the symmetry of the Pb0 silicon/oxide interface defects. For stresses up to 240 MPa, an increase in the pinning energy of 0.16 meV/MPa is observed for compressive stress, while for tensile stress it increases by 0.11 meV/MPa. Using the bulk, valence band deformation potentials the reduction in surface band bending in compression (0.09 meV/MPa) and in tension (0.13 meV/MPa) can be estimated.
关键词： Mechanical stress,Raman spectroscopy,X-ray photoelectron spectroscopy,Surface Fermi level pinning,Silicon,Interface defect
更新于2025-09-19 17:15:36
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How the methyl group position influences the ultrafast deactivation in aromatic radicals
摘要： Excited xylyl (methyl–benzyl) radical isomers have been studied by femtosecond time-resolved photoelectron spectroscopy and mass spectrometry. Depending on the substitution we find different deactivation channels after excitation into the D3(2A00) state (310 nm, 4 eV). While the ortho and para isomer exhibit deactivation rates similar to the benzyl radical, meta-xylyl sticks out and depletes twice as fast into the vibrationally hot ground state. We found that a ring deformation mode rather than the methyl pseudorotation enables access to a conical intersection, which is responsible for the faster deactivation. Transitions in the photoelectron spectrum can be assigned to several Rydberg series with mostly d angular momentum components. Absorption of two 4 eV photons triggers hydrogen loss reactions on a femtosecond timescale.
关键词： photoelectron spectroscopy,mass spectrometry,conical intersection,Rydberg states,femtosecond spectroscopy,ultrafast deactivation,xylyl radicals
更新于2025-09-19 17:15:36
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Photoelectron Spectroscopy of the Hexafluorobenzene Cluster Anions: (C<sub>6</sub>F<sub>6</sub>)<sub><i>n</i></sub><sup>?</sup> (<i>n</i> = 1 – 5) and I<sup>?</sup>(C<sub>6</sub>F<sub>6</sub>)
摘要： Frequency-resolved (2D) photoelectron (PE) spectra of the anionic clusters (C6F6)n?, for n = 1 – 5, and time-resolved PE spectra of I?C6F6 are presented using a newly built instrument and supported by electronic structure calculations. From the 2D PE spectra, the vertical detachment energy (VDE) of C6F6? was measured to be 1.60 ± 0.01 eV and the adiabatic detachment energy (ADE) ≤ 0.70 eV. The PE spectra also contain fingerprints of resonance dynamics over certain photon energy ranges, in agreement with the calculations. An action spectrum over the lowest resonance is also presented. The 2D spectra of (C6F6)n? show that the cluster can be described as C6F6?(C6F6)n?1. The VDE increases linearly (200 ± 20 meV n?1) due to the stabilising influence on the anion of the solvating C6F6 molecules. For I?C6F6, action spectra of the absorption just below both detachment channels are presented. Time-resolved PE spectra of I?C6F6 excited at 3.10 eV and probed at 1.55 eV reveal a short-lived non-valence state of C6F6? that coherently evolves into the valence ground state of the anion and induces vibrational motion along a specific buckling coordinate. Electronic structure calculations along the displacement of this mode show that at the extreme buckling angle, the probe can access an excited state of the anion that is bound at that geometry, but adiabatically unbound. Hence, slow electrons are emitted and show dynamics that probe predominantly the outer-turning point of the motion. A PE spectrum taken at t = 0 contains vibrational structure, assigned to a specific Raman and/or IR active mode of C6F6.
关键词： electron attachment,non-valence states,cluster anions,hexafluorobenzene,ultrafast dynamics,photoelectron spectroscopy
更新于2025-09-19 17:15:36
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Anion photoelectron spectroscopy of protein chromophores
摘要： Photoactive proteins that efficiently and selectively transfer light energy into a physical response are ubiquitous in nature. The small molecule chromophores that lie at the heart of these processes often exist as closed-shell anions following deprotonation in proton-transfer reactions. This review highlights the important role that anion photoelectron spectroscopy, combined with computational chemistry calculations, is playing in improving our understanding of the electronic structure and relaxation dynamics of these protein chromophores. We discuss key aspects of anion photoelectron spectroscopy. We then review recent anion photoelectron spectroscopy studies of the deprotonated chromophore anions found in green fluorescent protein (GFP), photoactive yellow protein (PYP) and the deprotonated luciferin anion found in the luciferase enzyme.
关键词： electrospray ionisation,Anion photoelectron spectroscopy,photoactive yellow protein,luciferin,green fluorescent protein,photodetachment
更新于2025-09-19 17:15:36