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Electronic structure and optical properties of Ln(III) nitrate adducts with 1,10-phenanthroline
摘要： Adducts of tris-nitrates of rare-earth elements Ce(III), Nd(III), Eu(III), and Er(III) with two molecules of 1,10-phenanthroline with formula Ln(NO3)3(Phen)2 are studied by X-ray photoelectron spectroscopy (XPS) and quantum chemistry (DFT/TDDFT). The geometric structure for DFT modeling is build using X-ray diffraction data. To analyze the composition and differences of the electronic structure in the series under study, XPS spectra were obtained for which interpretation was performed using calculated data. It has been shown that the molecule of Phen, when attached to the complexes of nitrates, is polarized, leads to an increase in absorption in the visible region and reduces the energy gap between HOMO and LUMO. Experimental absorption spectra were obtained, described and interpreted using TDDFT simulation. The transitions in adducts from π to π * MO in Phen ligands determine the main absorption band. The reasons for the absence of luminescence in adducts with ions Ce(III), Nd(III), and Er(III) are revealed by the example of the correlation diagram of singlet and triplet levels. A possible origin of coloring of adducts is determined using TDDFT.
关键词： Optical properties,Nitrates,DFT,Lanthanide ions,Photoelectron spectroscopy
更新于2025-09-19 17:15:36
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Studying the influence of deposition temperature and nitrogen contents on the structural, optical, and electrical properties of N-doped SnO2 films prepared by direct current magnetron sputtering
摘要： This report focuses on studying and investigating in detail the structural, electrical, and optical properties of p-type N-doped SnO2 (NTO) versus the deposition temperature and nitrogen content. P-type transparent conductive NTO films were deposited on quartz glass substrates using a direct current (DC) magnetron sputtering method. The substitution of oxygen by nitrogen in the SnO2 host lattice was verified using measurements such as X-ray photoelectron spectroscopy. The position of the N3? defect state in the band gap was determined using photoluminescence and ultra-violet-visible spectroscopy measurements. The data for the (110) to (101) rutile lattice planes changed, and the rutile (plane (101)) to cubic (plane (111)) SnO2 phase transition indicated the substitution of oxygen by nitrogen in the SnO2 host lattice. The best p-type conductive properties achieved were 8 × 10?2 Ω cm, 1.36 × 1019 cm?3, and 6.75 cm2 V?1 s?1 for the resistivity, hole concentration, and hole mobility, respectively, for film deposited at the optimum substrate temperature of 300 °C in a gas mixture of Ar and 50% N2.
关键词： deposition temperature,nitrogen content,p-type N-doped SnO2 thin film,X-ray photoelectron spectroscopy,DC magnetron sputtering,X-ray diffraction
更新于2025-09-19 17:15:36
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High-flux ultrafast extreme-ultraviolet photoemission spectroscopy at 18.4?MHz pulse repetition rate
摘要： Laser-dressed photoelectron spectroscopy, employing extreme-ultraviolet attosecond pulses obtained by femtosecond-laser-driven high-order harmonic generation, grants access to atomic-scale electron dynamics. Limited by space charge effects determining the admissible number of photoelectrons ejected during each laser pulse, multidimensional (i.e. spatially or angle-resolved) attosecond photoelectron spectroscopy of solids and nanostructures requires high-photon-energy, broadband high harmonic sources operating at high repetition rates. Here, we present a high-conversion-efficiency, 18.4-MHz-repetition-rate cavity-enhanced high harmonic source emitting 5 × 10^5 photons per pulse in the 25-to-60-eV range, releasing 1 × 10^10 photoelectrons per second from a 10-μm-diameter spot on tungsten, at space charge distortions of only a few tens of meV. Broadband, time-of-flight photoelectron detection with nearly 100% temporal duty cycle evidences a count rate improvement between two and three orders of magnitude over state-of-the-art attosecond photoelectron spectroscopy experiments under identical space charge conditions. The measurement time reduction and the photon energy scalability render this technology viable for next-generation, high-repetition-rate, multidimensional attosecond metrology.
关键词： attosecond science,photoelectron spectroscopy,high-harmonic generation,cavity enhancement,ultrafast lasers
更新于2025-09-19 17:15:36
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Surface CH <sub/>3</sub> NH <sub/>3</sub><sup>+</sup> to CH <sub/>3</sub><sup>+</sup> Ratio Impacts the Work Function of Solution-Processed and Vacuum-Sublimed CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3</sub> Thin Films
摘要： CH3NH3PbI3 thin films are fabricated using several representative synthesis methods such as spin-coating, evaporation, and a combination of the two. These methods, which frequently occur in reported literatures, use the same precursors PbI2 and CH3NH3I but differ in how the two are mixed. It is found that the latter plays a vital role in determining the surface morphology, composition, and grain size of the films, even when the same stoichiometric ratio of the precursors is used. X-ray photoelectron spectroscopy reveals that the amount of CH3+ -type defects, which results from CH3NH3I dissociation, is sensitive to both the physical state of CH3NH3I and the order of mixing sequence. The variation of the CH3NH3+ ratio also affects the valence band and the work function of the corresponding films, as revealed by ultraviolet photoelectron spectroscopy. Furthermore, the energy-level alignment between the perovskite film and a model hole transport layer, N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine (NPB) is examined. It is found that the CH3NH3+ ratio correlates with the offsets between the valence band maximum of perovskite film and the highest occupied molecular orbital of NPB as well, and the energy-level alignment with the dual-source, coevaporated CH3NH3PbI3 film is most suitable for efficient hole transport.
关键词： electronic structure,methylammonium lead triiodide,solution synthesis,physical evaporation,photoelectron spectroscopy
更新于2025-09-19 17:15:36
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On the Adherence of Chemically Deposited CdS Films to Common Inorganic Substrates: Effect of Cd <sup>2+</sup> Concentration in Solution, Substrate Surface Chemistry, and Reaction Temperature
摘要： The bad adherence to the substrate of chemical-solution-deposited chalcogenide films in alkaline solution is a current technological problem. However, this issue is belittled since is commonly solved by employing pre-sensitized substrates or by empirically changing the deposition parameters until 'finding' the 'proper' chemical formulation. For these reasons, the issue of the adherence has not been previously studied. The present research aims to properly discuss the issue of adherence by taking as example CdS. As a substrate, we used float glass sheets to take advantage of this interesting flat glass (different tin content). It was found that both the surface chemical composition of the substrate and the concentration of Cd2+ in the reaction solution play important roles in the adherence of the CdS thin films; an important effect of temperature was also found. The results were also consistent for indium tin oxide and silicon wafer surfaces. We propose a general surface reaction scheme which considers both the surface reactive sites and the hidroxo–cadmium–thiourea complexes of the reaction solution, as well as the formation of a surface intermediate entity which dissociates into a CdS molecule bonded to the surface and byproducts. The adherence depends on the quantity of surface intermediate entities formed, and therefore, the conditions that promote their formation contribute to the adherence: high reagent concentration, high-reactive surface sites, and low reaction temperature.
关键词： Float Glass,X-Ray Photoelectron Spectroscopy (XPS),Chemical Bath Deposition,Film Adherence,Tin Oxide
更新于2025-09-19 17:15:36
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Epitaxial growth and determination of the band alignment for NixMg1-xO/MgO interface by laser molecular beam epitaxy
摘要： By laser molecular beam epitaxy, single crystalline NixMg1-xO films have been successfully synthesized on MgO(100) surface. The in situ reflection high-energy electron diffraction patterns show that the induced O2 background gas with at least 1.0 × 10?3 Pa is necessary to the epitaxial growth of NixMg1-xO films. The X-ray diffraction patterns reveal the single-phase growth along (200) direction. The energy band alignment at the interface is investigated by employing in situ X-ray photoelectron spectroscopy. The valence band offsets are determined to be from 1.47 eV to 1.50 eV with the decrease of Ni content (0.39 / 0.35). Furthermore, the work function is evaluated by using in situ ultraviolet photoemission spectroscopy, indicating the values from 4.33 eV to 4.64 eV. This study provides a promising guidance for the solar-blind device design and fabrication.
关键词： Work function,X-ray photoelectron spectroscopy,Band alignment,Ultraviolet photoemission spectroscopy,Laser molecular beam epitaxy
更新于2025-09-19 17:13:59
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Indium sulfide based metal-semiconductor-metal ultraviolet-visible photodetector
摘要： In recent years, the photodetectors gained much attention due to their wide range of applications in industry, military, space and biological fields. In this work, the metal-semiconductor-metal (MSM) photodetector was fabricated using In2S3 thin films with Al interdigitated electrodes. The In2S3 thin films were prepared by co-evaporation technique with various thicknesses in the range 130–700 nm at a constant substrate temperature of 350 ?C. The structural, morphological, compositional, optical and electrical properties of In2S3 thin films were studied as a function of thickness. The energy band gap of films is found to be in the range 2.53–2.71 eV. I–V characteristics and photo response of photodetectors were recorded under UV and visible light illumination. The parameters of a photodetector such as photo sensitivity, responsivity and detectivity were calculated. The observed photo responsivity increases with increase of film thickness. The photo response of all photodetectors confirmed the stable and reproducible characteristics such as photo sensitivity, responsivity and detectivity.
关键词： Williamson-Hall plot,Co-evaporation,X-ray photoelectron spectroscopy,Ultraviolet-visible photodetector,Indium sulfide thin films
更新于2025-09-19 17:13:59
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Enhanced thermal stability of InP quantum dots coated with Al-doped ZnS shell
摘要： Colloidal InP quantum dots (QDs) have attracted a surge of interest as environmentally friendly light-emitters in downconversion liquid crystal displays and light-emitting diodes (LEDs). A ZnS shell on InP-based core QDs has helped achieve high photoluminescence (PL) quantum yield (QY) and stability. Yet, due to the difficulty in the growth of a thick ZnS shell without crystalline defects, InP-based core/shell QDs show inferior stability against QY drop compared to Cd chalcogenide precedents, e.g., CdSe/CdS core/thick-shell QDs. In this work, we demonstrate the synthesis of InP-based core/shell QDs coated with an Al-doped ZnS outer shell. QDs with an Al-doped shell exhibit remarkable improvement in thermal and air stability even when the shell thickness is below 2 nm, while the absorption and PL spectra, size, and crystal structure are nearly the same as the case of QDs with a pristine ZnS shell. X-ray photoelectron spectroscopy reveals that Al3+ in Al-doped QDs forms an Al-oxide layer at elevated temperature under ambient atmosphere. The as-formed Al-oxide layer blocks the access of external oxidative species penetrating into QDs and prevents QDs from oxidative degradation. We also trace the chemical pathway of the incorporation of Al3+ into ZnS lattice during the shell growth. Furthermore, we fabricate QD-LEDs using Al-doped and undoped QDs and compare the optoelectronic characteristics and stability.
关键词： quantum yield,QD-LEDs,photoluminescence,Al-doped ZnS shell,X-ray photoelectron spectroscopy,InP quantum dots,thermal stability
更新于2025-09-19 17:13:59
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PFI-ZEKE-photoelectron spectroscopy of N <sub/>2</sub> O using narrow-band VUV laser radiation generated by four-wave mixing in Ar using a KBBF crystal
摘要： A new nonlinear optical scheme relying on sum-frequency mixing in a KBe2BO3F2 crystal has been used to generate intense, broadly tunable, narrow-bandwidth, coherent vacuum-ultraviolet (VUV) radiation beyond 16 eV by resonance-enhanced four-wave mixing in Ar. The VUV radiation was used to record high-resolution pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the N2O+ A+ ← N2O X photoionizing transition in the wave-number range from 132 000 cm?1 to 135 000 cm?1. The rotational structure of almost all vibrational levels of the A+ state with vibrational term values up to 2700 cm?1 could be resolved, and improved values of the first two adiabatic ionization energies of N2O, corresponding to the formation of the X+ 2Π3/2(000) J+ = 3/2 and A+ 2Σ+(000) N+ = 0 levels of N2O+ from the X 1Σ+(000) J′′ = 0 ground state [103 969.30(12) cm?1 and 132 197.70(12) cm?1, respectively], were derived. The rotational intensity distributions of the bands were found to depend strongly on the value of the vibrational angular momentum of the ionic levels. The vibrational structure is discussed in terms of previously reported effective-Hamiltonian analyses.
关键词： KBBF crystal,PFI-ZEKE-photoelectron spectroscopy,N2O,narrow-band VUV laser radiation,four-wave mixing
更新于2025-09-19 17:13:59
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Band-energy estimation on silicon cap annealed 4H-SiC surface using hard X-ray photoelectron spectroscopy
摘要： Silicon-cap annealing (SiCA) emerged as a promising silicidation-less ohmic contact formation method that can solve the crucial reliability limitation of ohmic contacts formed with metals; this limitation was due to carbon aggregation introduced during silicidation annealing. However, no previous study for a complete understanding of SiCA effects on the metal/SiC exists. In this study, the band-energy state of silicidation-less ohmic contacts formed by SiCA-SiC is directly estimated using hard X-ray photoelectron spectroscopy (HAXPES). The results show that Si-dot formation on the SiC surface reduces the contacts resistivity, and ohmic contact behavior is still observed even after Si-dot removal. A peak position analysis of Si 1 s orbit using HAXPES shows a clear increase in the band energy under various SiC surface conditions. Particularly, the Al/SiCA-SiC sample shows a peak shift of 0.765 eV. This strong potential barrier lowering the derived formation of the thin-depletion layer and low potential barrier on Al/SiCA-SiC junction. Moreover, the observations made using HAXPES, and transmission electron microscopy, suggest that the modification of the outer-most surface layer plays an essential role in the ohmic contact formation. These results provide insights on the ohmic contact formation mechanism for wide-band-gap semiconductor materials.
关键词： 4H-SiC,silicidation-less ohmic contact,Ohmic contacts,silicon-cap annealing,Hard X-ray photoelectron spectroscopy
更新于2025-09-19 17:13:59