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Understanding core level shifts in aromatic compounds is crucial for the correct interpretation of x-ray photoelectron spectroscopy (XPS) of polycyclic aromatic hydrocarbons (PAHs), including acenes, as well as of styrenic polymers, which are increasingly relevant for the microelectronic industry, among other applications. The effect of delocalization through π aromatic systems on the stabilization of valence molecular orbitals has been widely investigated in the past. However, little has been reported on the impact on the deeper C1s core energy levels. In this work, we use first-principles calculations at the level of many body perturbation theory to compute the C1s binding energies of several aromatic systems. We report a C1s red shift in PAHs and acenes of increasing size, both in the gas phase and in the molecular crystal. C1s red shifts are also calculated for stacked benzene and naphthalene pairs at decreasing intermolecular distances. A C1s red shift is in addition found between oligomers of poly(p-hydroxystyrene) and polystyrene of increasing length, which we attribute to ring–ring interactions between the side-chains. The predicted shifts are larger than common instrumental errors and could, therefore, be detected in XPS experiments. [ABSTRACT FROM AUTHOR]

One of the challenges in the semiconductor industry is to find new barrier materials and copper (Cu) alternative solutions in interconnects. In this work, we focused to find alternative diffusion barrier materials. Different binary (CoMo, CoRu, CoTa, CoW, MoRu, RuTa, RuW) and ternary (CoMoTa, CoRuTa, MoRuTa) metal alloys were evaluated theoretically with the Miedema model to find the amorphous phase composition range. Afterward, thin films of the alloys with various compositions were deposited by magnetron sputtering and theoretical values were compared to the experimental results. From the experimental measurements, which included grazing incidence x-ray diffraction analysis and resistivity measurements, suitable binary and ternary alloys were chosen for diffusion analysis. By annealing thin film stacks at temperatures ranging from 500 to 675 ° C, diffusion was induced and detected by x-ray photoelectron spectroscopy depth profiles. Seventeen alloys were evaluated by their diffusion barrier effectiveness, and five of those, which include Ru 60 Ta 40 , Ru 45 W 55 , Mo 47 Ru 53 , Mo 36 Ru 50 Ta 14 , and Co 40 Mo 35 Ta 25 , showed excellent barrier properties against copper diffusion. Furthermore, all of the stated materials have a lower resistivity than TaN. Last, the adhesion of the best performing alloys to SiCOH and Cu was evaluated by the modified edge lift-off test. Only Ru 45 W 55 had reasonable adhesion at both interfaces. The other materials showed low adhesion strength to Cu, which would make an adhesion promoter (liner), such as cobalt, necessary for the integration. [ABSTRACT FROM AUTHOR]

The interaction between ammonia (NH3) and (alumino)silicates is of fundamental and applied importance, yet the specifics of NH3 adsorption on silicate surfaces remain largely unexplored, mainly because of experimental challenges related to their electrically insulating nature. An example of this knowledge gap is evident in the context of ice nucleation on silicate dust, wherein the role of NH3 for ice nucleation remains debated. This study explores the fundamentals of the interaction between NH3 and microcline feldspar (KAlSi3O8), a common aluminosilicate with outstanding ice nucleation abilities. Atomically resolved non-contact atomic force microscopy, x-ray photoelectron spectroscopy, and density functional theory-based calculations elucidate the adsorption geometry of NH3 on the lowest-energy surface of microcline, the (001) facet, and its interplay with surface hydroxyls and molecular water. NH3 and H2O are found to adsorb molecularly in the same adsorption sites, creating H-bonds with the proximate surface silanol (Si–OH) and aluminol (Al–OH) groups. Despite the closely matched adsorption energies of the two molecules, NH3 readily yields to replacement by H2O, challenging the notion that ice nucleation on microcline proceeds via the creation of an ordered H2O layer atop pre-adsorbed NH3 molecules. [ABSTRACT FROM AUTHOR]

This paper describes a three-step process to remediate surface and sub-surface defects on chemo-mechanically polished SiC surfaces. In this process, a CF4-based inductively coupled plasma with reactive ion etch was used to remove material to a depth, which is unaffected by surface and subsurface polishing damage. This produced a planarized but carbon-rich fluorinated surface. This surface was then exposed to a 2 min rapid thermal oxidation in air at 1000 °C to oxidize and volatilize the excess carbon and fluorinated species, respectively. The resulting surface oxide was then stripped using a dilute hydrofluoric acid in water solution. This process, referred to as plasma assisted remediation, reproducibly yielded planarized, stoichiometric surfaces with low levels of carbon and oxygen contamination suitable for subsequent device fabrication. In the supporting studies described here, 4H- and 6H-SiC(0001) surfaces were remediated and characterized by x-ray photoelectron spectroscopy and atomic force microscopy at each stage of the process. Experimental studies under ion-rich and radical-dominant conditions are also reported which provide greater insight into the underlying chemistry and physics of the process. [ABSTRACT FROM AUTHOR]

Borazine is a well-established precursor molecule for the growth of hexagonal boron nitride (h-BN) via chemical vapor deposition on metal substrates. To understand the formation of the h-BN/Rh(111) moiré from borazine on a molecular level, we investigated the low-temperature adsorption and thermally induced on-surface reaction of borazine on Rh(111) in situ using synchrotron radiation-based high-resolution x-ray photoelectron spectroscopy (XPS), temperature-programmed XPS, and near-edge x-ray absorption fine structure measurements. We find that borazine adsorbs mainly as an intact molecule and have identified a flat-lying adsorption geometry. Borazine multilayers are observed to desorb below 200 K. Starting at about 300 K, dehydrogenation of the remaining borazine and borazine fragments takes place, and disordered boron nitride starts to grow. Above 600 K, the formation of the h-BN sets in. Finally, at 1100 K, the conversion to h-BN is complete. The h-BN formed by deposition and post-annealing was compared to the h-BN grown by an established procedure, proving the successful preparation of the desired two-dimensional material. [ABSTRACT FROM AUTHOR]

MnO(001) thin films were grown on commercial MgO(001) substrates at 520 °C by reactive molecular beam epitaxy (MBE) using Mn vapor and O2-seeded supersonic molecular beams (SMBs) both with and without radio frequency (RF) plasma excitation. For comparison, MnO(001) films were grown by reactive MBE using O2 from a leak valve. X-ray photoelectron spectroscopy confirmed the Mn2+ oxidation state and 10%–15% excess oxygen near the growth surface. Reflection high-energy electron diffraction and x-ray diffraction evidenced that the films were rock salt cubic MnO with very strong (001) orientation. High-angle annular dark field scanning transmission electron microscopy with energy-dispersive x-ray spectroscopy demonstrated abrupt MnO/MgO interfaces and indicated [(001)MnO||(001)MgO] epitaxial growth. Ex situ atomic force microscopy of films deposited without RF excitation revealed smooth growth surfaces. An SMB-grown MnO(001) film was converted to Mn3O4 with strong (110) orientation by post-growth exposure to an RF-discharge (RFD) SMB source providing O atoms; the surface of the resultant film contained elongated pits aligned with the MgO 110 directions. In contrast, using the RFD-SMB source for growth resulted in MnO(001) films with elongated growth pits and square pyramidal hillocks aligned along the MgO 110 and 100 directions, respectively. [ABSTRACT FROM AUTHOR]

Alloying CdTe absorbers with Se is a critical advancement for the fabrication of highly efficient CdTe thin-film solar cells. Herein, the role of the Se concentration gradient in CdSexTe1−x/CdTe solar cells is stressed in addition to the decreased bandgap and passivation effect of Se. The buried graded CdSexTe1−x at the front interface of the device was stripped and analyzed by quasi in situ x-ray photoelectron spectroscopy depth profiling. A serial shift of Fermi level toward the valence band was probed as the Se concentration decreased in the graded CdSexTe1−x absorber, revealing the presence of n-type CdSexTe1−x region near the front contact. Kelvin probe force microscopy characterizations and voltage-dependent photocurrent collection analysis further confirmed the existence of a buried junction in the graded CdSexTe1−x absorber. The CdS-free CdTe solar cell with a graded CdSexTe1−x/CdTe absorber fabricated in this study showed an efficiency of 17.6%. These results indicated that the non-uniform distribution of Se introduced a built-in field in the graded CdSexTe1−x absorber and enabled efficient separation of photogenerated carriers, yielding high-performance CdTe solar cells in the absence of a conventional n-type CdS window layer. This study deepened the understanding of the performance enhancement in Se-containing CdTe solar cells and provided new ideas for further performance optimization. [ABSTRACT FROM AUTHOR]

As initiated Chemical Vapor Deposition (iCVD) finds increasing application in precision industries like electronics and optics, defect prevention will become critical. While studies of non-ideal morphology exist in the iCVD literature, no studies investigate the role of defects. To address this knowledge gap, we show that the buildup of short-chain polymers or oligomers during normal operation of an iCVD reactor can lead to defects that compromise film integrity. We used atomic force microscopy to show that oligomer aggregates selectively prevented film growth, causing these hole-like defects. X-ray diffraction and optical microscopy demonstrated the crystallinity of the aggregates, pointing to a flat-on lamellar or mono-lamellar structure. To understand the origin of the aggregates, spectroscopic ellipsometry showed that samples exposed to the reactor consistently accrued low-volatility contaminants. X-ray photoelectron spectroscopy revealed material derived from polymerization in the contamination, while scanning electron microscopy showed the presence of defect-causing aggregates. We directly linked oligomeric/polymeric contamination with defect formation by showing an increased defect rate when a contaminant polymer was heated alongside the sample. Most importantly, we showed that starting a deposition at a high sample temperature (e.g., 50 °C) before reducing it to the desired setpoint (e.g., 9 °C) unilaterally prevented defects, providing a simple method to prevent defects with minimal impact on operations. [ABSTRACT FROM AUTHOR]

Ultrawide bandgap ZnGa2O4 (ZGO) thin films were grown on sapphire (0001) substrates at various growth temperatures with a perspective to investigate the electrical and optical characteristics required for high-power electronic applications. Due to the variation in the vapor pressure of Zn and Ga, severe loss of Zn was observed during pulsed laser deposition, which was solved by using a zinc-rich Zn0.98Ga0.02O target. A pure phase single-crystalline ZGO thin film was obtained at a deposition temperature of 750 °C and an oxygen pressure of 1 × 10−2 Torr. The out-of-plane epitaxial relationship between the sapphire and ZGO thin film was obtained from φ-scan. The x-ray rocking curve of the ZGO thin film grown at 750 °C exhibits a full width at half maximum of ∼0.098°, which indicates a good crystalline phase and quality of the thin film. Core-level x-ray photoelectron spectroscopy of ZGO grown at 750 °C indicated that Zn and Ga were in the 2+ and 3+ oxidation states, respectively, and the atomic ratio of Zn/Ga was estimated to be ∼0.48 from the fitted values of Zn-2p3/2 and Ga-2p3/2. The high-resolution transmission electron microscopy images revealed a sharp interface with the thickness of the ZGO film of ∼265 nm, and the signature of minor secondary phases was observed. The bandgap of the ZGO film at different growth temperatures was calculated from the ultraviolet-diffuse reflectance spectroscopy spectra, and its value was obtained to be ∼5.08 eV for the 750 °C grown sample. The refractive index (n) and the extinction coefficient (k) were determined to be ∼1.94 and 0.023 from the ellipsometric data, respectively, and the real dielectric function (ɛr) was estimated to be ∼6.8 at energy 5 eV. The ultrawide bandgap and dielectric function of ZGO recommend its possible potential applications in deep-ultraviolet optoelectronic devices and high-power electronics. [ABSTRACT FROM AUTHOR]

In this work, three atomic layer deposition (ALD) approaches are used to deposit an Al2O3 gate insulator on n-GaN for application in vertical GaN power switches: thermal ALD (ThALD), plasma-enhanced ALD (PEALD), and their stacked combination. The latter is a novel method to yield the most ideal insulating layer. Also, the influence of an in situ NH3 or H2 plasma pre-treatment is studied. Planar MIS capacitors are used to investigate the electrical properties and robustness of the gate insulators. In vacuo x-ray photoelectron spectroscopy (XPS) is used to study the changes in chemical composition after every surface treatment. XPS shows that all plasma pre-treatments efficiently remove all carbon contamination from the surface, but only NH3 plasma is observed to additionally remove the native oxide from the n-GaN surface. The water precursor step in the ThALD process does not completely remove the CH3 ligands of the trimethylaluminum precursor step, which might electrically be associated with a reduced forward bias robustness. The O2 plasma step in the PEALD process is associated with the removal of carbon and a tremendous increase of the O content in the GaN surface region. Electrically, this strongly correlates to an enhanced forward bias robustness and an increased forward bias hysteresis, respectively. The ThALD/PEALD stack method mitigates the shortcomings of both ALD processes while maintaining its advantages. Electrical measurements indicate that the stack method alongside NH3 plasma pretreatment provides the best characteristics in terms of hysteresis, threshold voltage, forward bias robustness, and interface trap density of states. [ABSTRACT FROM AUTHOR]

As water pollution is increasing due to industrialization, there is a high demand for easy-processing photocatalytic materials to clean wastewater. Here, the improvement in the photocatalytic dye degradation effect of graphene oxide (GO) surfaces, made of ultra-sonication assisted modified Hummer's method, is demonstrated with increasing alumina (Al2O3) concentration in the range of 4–30 wt. %. Scanning electron microscopy and x-ray diffraction results suggest a gradual increment in crystalline Al2O3 nanoparticles (NPs) by reducing GO, in good agreement with the first-principles calculations. Moreover, x-ray photoelectron spectroscopy reveals the appearance of oxygenated functional groups with increasing Al2O3 concentration, leading to the formation of defect-rich GO as demonstrated by Raman spectroscopy. Ultraviolet-visible spectroscopy further reflects a maximum reduction in the optical bandgap from 1.88 to 1.56 eV up to a concentration of 15 wt. % Al2O3. Interestingly, the methylene blue degradation efficiency of GO under ultraviolet irradiation is also found to be improved from 45% to 64% with 15 wt. % Al2O3, whereas the formation of Al2O3 NPs in the range of 100–300 nm with 30 wt. % Al2O3 is found to be detrimental for photocatalytic activity. [ABSTRACT FROM AUTHOR]

Atmospheric plasma etching (APE) has been used to texture Si surfaces due to anisotropic material removal capability. Controlling features and size of the light-trapping structure are keys to improving the reflection performance of silicon (Si) solar cells, which need to fully understand the interfacial etching behavior and the microscopic topography formation mechanism of the Si surface. In this study, microwave plasma with a temperature below 100 °C is employed to investigate the dependence of microstructure evolution on the O/F atom ratios in plasma. The results show that as the O/F atom ratios increase, the microstructure of the Si surface changes from square opening pits to spherical opening pits. High-resolution transmission electron microscopy and x-ray photoelectron spectroscopy analyses indicate that the exciting F atoms dominate the orientation-selective etching process, causing the formation of square opening pits. The CFx and C2 radicals induce the generation of the Si interface reactive layer, resulting in the occurrence of amorphous layers and termination of the non ⟨111⟩-crystal face in APE. The exciting O atoms preferentially occupy the active site of Si surfaces, causing the isotropic etching and then the formation of spherical opening pits. In addition, the richer O atoms will weaken the anisotropic etching ability of F atoms, resulting in the etched surface trends' flattening. The insight into anisotropic etching behavior and topography formation mechanism of the silicon surface textured by atmospheric plasma is valuable for developing a new texturing approach to silicon solar cells. [ABSTRACT FROM AUTHOR]

TiO2 and SrTiO3 are stable and efficient materials for photoelectrochemical (PEC) water splitting. PEC activity is influenced by carrier recombination in crystals of these materials. In this study, we analyzed the effect of dislocations on carrier recombination in TiO2 and SrTiO3 using microwave photoconductive decay measurements on polished and unpolished faces. The apparent slow decay in the unpolished face implies that dislocations trap minority carriers. Based on the different dependences of the injected photon density and temperature, the recombination processes in the polished and unpolished faces differ. A high concentration of oxygen vacancies or hydroxyl in the unpolished face of SrTiO3 was observed by x-ray photoelectron spectroscopy, and dislocations in the unpolished faces of both materials were observed using transmission electron microscopy. Additionally, we found that the photocurrent duration in the unpolished faces was shorter than that in the polished faces for both TiO2 and SrTiO3, confirming that dislocations inhibited photoelectrochemical activity. [ABSTRACT FROM AUTHOR]

The discovery of strontium niobate (SNO) as a potentially new transparent electrode has generated much interest due to its implications in various optoelectronic devices. Pristine SNO exhibits exceptionally low resistivity (∼10−4 Ω cm) at room temperature. However, this low resistivity occurs due to large number of carrier concentration in the system, which significantly affects its optical transparency (∼40%) in the visible range and hinders its practical applications as a transparent electrode. Here, we show that modulating the growth kinetics via oxygen manipulation is a feasible approach to achieve the desired optoelectronic properties. In particular, epitaxial (001) SNO thin films are grown on (001) lanthanum aluminate by pulsed laser deposition at different oxygen partial pressures and are shown to improve the optical transparency from 40% to 72% (λ = 550 nm) at a marginal cost of electrical resistivity from 2.8 to 8.1 × 10−4 Ω cm. These changes are directly linked with the multi-valence Nb-states, as evidenced by x-ray photoelectron spectroscopy. Furthermore, the defect-engineered SNO films exhibit multiple electronic phases that include pure metallic, coexisting metal-semiconducting-like, and pure semiconducting-like phases as evidenced by low-temperature electrical transport measurements. The intriguing metal-semiconducting coexisting phase is thoroughly analyzed using both perpendicular and angle-dependent magnetoresistance measurements, further supported by a density functional theory-based first-principles study and the observed feature is explained by the quantum correction to the conductivity. Overall, this study shows an exciting avenue for altering the optical and transport properties of SNO epitaxial thin films for their practical use as a next-generation transparent electrode. [ABSTRACT FROM AUTHOR]

Ti-doped In 2 O 3 thin films with varying Ti contents are prepared by partial reactive co-sputtering using ceramic In 2 O 3 and metallic Ti targets and characterized by in situ x-ray photoelectron spectroscopy, electrical conductivity, and Hall-effect measurements. For a substrate temperature of 400 ° C , the carrier concentration increases faster than the Ti content and saturates at ≈ 7.4 × 10 20 c m − 3 . Based on these results, it is suggested that Ti does not directly act as donor in In 2 O 3 but is rather forming TiO 2 precipitates and that the related scavenging of oxygen generates oxygen vacancies in In 2 O 3 as origin of doping. Neutralization of oxygen vacancies is, therefore, suggested to be origin of the limitation of the carrier concentration in Ti-doped In 2 O 3 films. [ABSTRACT FROM AUTHOR]

Transition metal oxides provide opportunities to induce and modulate the superconducting state, due to the delicate interplay between charge, spin, orbital, and lattice order. In this work, 5d transition metal oxide SrTaO3 films were deposited by pulsed laser deposition, and an anomalous negative resistance was observed. The negative resistance can be ascribed to the nonuniform conductivity, associated with nonuniform electronic states in the SrTaO3 thin films, as confirmed by conductive atomic force microscopy and x-ray photoelectron spectroscopy. Moreover, a sharp drop in the resistance together with a decrease in magnetization was observed at around 40 K. This might imply a possible superconducting state. The negative resistance can be well explained based on an equivalent circuit comprising normal and superconductive states, also supporting the possible superconducting state in SrTaO3 thin films. This work promotes the exploring and revealing of the mechanism in tantalates superconductivity. [ABSTRACT FROM AUTHOR]

We investigate a synaptic device with short-term memory characteristics using IGZO/SnOx as the switching layer. The thickness and components of each layer are analyzed by using x-ray photoelectron spectroscopy and transmission electron microscopy. The memristor exhibits analog resistive switching and a volatile feature with current decay over time. Moreover, through ten cycles of potentiation and depression, we demonstrate stable conductance modulation, leading to high-accuracy Modified National Institute of Standards and Technology pattern recognition. We effectively emulate the learning system of a biological synapse, including paired-pulse facilitation, spiking-amplitude-dependent plasticity, and spiking-rate-dependent plasticity (SRDP) by pulse trains. Ultimately, 4-bit reservoir computing divided into 16 states is incarnated using a pulse stream considering short-term memory plasticity and decay properties. [ABSTRACT FROM AUTHOR]

Silicene, a 2D hexagonal structure of silicon, has shown great promise for next-generation advanced electronic devices due to recent progress. However, one major obstacle to its application and integration into devices is its strong tendency of rapid oxidation in an ambient environment. Enhancing the chemical inertness by means of chemical modification without comprising its unique structure and properties is vital. Here, we report the fabrication of hydrogenated silicene grown on polycrystalline Ag films by means of plasma-enhanced chemical-vapor deposition (PECVD) with proper hydrogen dilution. Our Raman spectroscopy and x-ray diffraction results show the existence of typical monolayer and few-layer silicene. The x-ray photoelectron spectroscopy demonstrates its oxidation resistance after a few minutes of air exposure in a class 100 clean room. We propose that PECVD silicene can be an alternative to molecular-beam-epitaxy silicene for potential low-cost and large-area silicene applications. [ABSTRACT FROM AUTHOR]

This study investigated the improvement of the electro-optical properties of a liquid crystal (LC) cell fabricated through brush coating using graphene oxide (GO) doping. The physical deformation of the surface was analyzed using atomic force microscopy. The size of the groove increased as the GO dopant concentration increased, but the direction of the groove along the brush direction was maintained. X-ray photoelectron spectroscopy analysis confirmed that the number of C–C and O–Sn bonds increased as the GO concentration increased. Since the van der Waals force on the surface increases as the number of O–metal bonds increases, we were able to determine why the anchoring energy of the LC alignment layer increased. This was confirmed by residual DC voltage and anchoring energy measurements that were later performed. As the GO concentration increased, the width of the hysteresis curve decreased, indicating that the residual DC voltage decreased. Additionally, the 15% GO-doped sample exhibited a significant increase in its anchoring energy up to 1.34 × 10−3 J/m2, which is similar to that of rubbed polyimide. It also secured a high level of electro-optical properties and demonstrated potential as a next-generation thin-film display despite being produced via a simple brush-coating process. [ABSTRACT FROM AUTHOR]

Enantio-discrimination and spin-dependent electrochemistry (SDE), as a manifestation of the chirality-induced spin selectivity (CISS) effect, are important phenomena that can be probed by "chiral" electrochemistry. Here, we prepared chiralized surfaces of gold and nickel, to serve as working electrodes, through effective chemisorption of enantiopure dimethyl-bis(ethylenedithio)-tetrathiafulvalene (DM-BEDT-TTF) 1, tetramethyl-bis(ethylenedithio)-tetrathiafulvalene (TM-BEDT-TTF) 2, and their capped silver nanoparticle (AgNPs) aggregate by simple incubation of the metallic substrates. The effective chemisorption was checked by means of ultrahigh vacuum x-ray photoelectron spectroscopy (XPS) and by electro-desorption experiments, i.e., cyclic voltammetry (CV) scans showing a first electro-desorption peak at about −1.0 V. The Au|1 and Au|2 chiral electrodes were successfully used in CV experiments exploiting chiral redox probes. Finally, the hybrid interfaces Ni|enantiopure 1 or 2|AgNPs served as working electrodes in SDE experiments. In particular, the hybrid chiral interfaces Ni|(R)-2|AgNPs and Ni|(S)-2|AgNPs exhibited a significant spin-filtering ability, as a manifestation of the CISS effect, with average spin polarization values of 15%. [ABSTRACT FROM AUTHOR]

GeSnC alloys offer a route to direct bandgap semiconductors for CMOS-compatible lasers, but the use of CBr4 as a carbon source was shown to reduce Sn incorporation by 83%–92%. We report on the role of thermally cracked H in increasing Sn incorporation by 6x–9.5x, restoring up to 71% of the lost Sn, and attribute this increase to removal of Br from the growth surface as HBr prior to formation of volatile groups such as SnBr4. Furthermore, as the H flux is increased, Rutherford backscattering spectroscopy reveals a monotonic increase in both Sn and carbon incorporation. X-ray diffraction reveals tensile-strained films that are pseudomorphic with the substrate. Raman spectroscopy suggests substitutional C incorporation; both x-ray photoelectron spectroscopy and Raman suggest a lack of graphitic carbon or its other phases. For the lowest growth temperatures, scanning transmission electron microscopy reveals nanovoids that may account for the low Sn substitutional fraction in those layers. Conversely, the sample grown at high temperatures displayed abrupt interfaces, notably devoid of any voids, tin, or carbon-rich clusters. Finally, the surface roughness decreases with increasing growth temperature. These results show that atomic hydrogen provides a highly promising route to increase both Sn and C to achieve a strongly direct bandgap for optical gain and active silicon photonics. [ABSTRACT FROM AUTHOR]

Bandpass filters (BPFs) are optical filters with significantly high transmittance in a specific wavelength range and low transmittance on both sides. Infrared BPFs can reduce system losses and overheating caused by other light wavelengths owing to their ability to selectively transmit infrared light of the desired wavelength. This article discusses the potential of using a high refractive index material, β-FeSi2, in BPFs. To the best of our knowledge, no studies have applied β-FeSi2 to infrared BPFs. Simulation results showed that its high refractive index allows the excellent performance of the BPF to be achieved using a multilayer thin film structure with only three layers. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy results showed that the β-FeSi2 thin film exhibited the lowest absorptance of approximately 0 when the correct stoichiometry (Fe:Si = 1:2) was achieved through co-sputtering. Based on these findings, a β-FeSi2/SiO2/β-FeSi2 multilayer thin film was designed to fabricate the BPF. The fabricated BPF exhibited a narrow peak and achieved a peak transmittance exceeding 80%. This suggested that β-FeSi2 is a promising material for fabricating infrared BPFs. Utilizing these filters is expected to yield significant efficiency improvements and reduce losses across various applications, including thermophotovoltaics and infrared heaters. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy (XPS) is generally used for chemical analysis of surfaces and interfaces. This method involves the analysis of changes in binding energies and peak shapes of elements under consideration. It is also possible to use XPS to study the effect of x-ray radiation on the electrical properties of thin films. We measured the Si 2p peak using x-ray powers of 300 and 150 W on ∼135 nm silicon dioxide (SiO2) thin films grown on both n- and p-type substrates while applying DC or AC external biases. Using the shifts in the binding energy of the Si 2p peak, we calculated the resistances and the capacitances of the SiO2 thin film. The way that the binding energies of the Si 2p peak and the capacitance of the thin film change as a function of the type of Si substrate and the power of the x-ray are explained using band bending. [ABSTRACT FROM AUTHOR]

InAs nanowires (NWs) were grown on SiOx pinholes formed on Si(111) substrates by molecular beam epitaxy. Influences of electron-beam (EB) irradiation on the SiOx layer on the pinhole formation and the subsequent InAs NW growth were studied. As the EB irradiation dose increased, the pinhole density in the SiOx layer decreased. From atomic force microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy results, it was found that the pinhole etching of the SiOx layer by Ga droplets was suppressed by carbon adsorption due to the EB irradiation. By forming high-density pinholes on the SiOx layer without the EB irradiation, high-density InAs NWs with 1–2 × 1010 cm−2 were grown successfully, and the uniformity in the NW diameter improved. The standard deviation of the NW diameter was 1.8 nm (8.8%) for high-density NWs. In addition, the NW diameter decreased with decreasing EB dose, and the NW diameter was controlled by adjusting the diameter of Ga droplets forming the pinholes. As the NW diameter decreased, photoluminescence spectra of the NWs shifted to higher energies than the bandgap energy of the wurtzite InAs bulk. From these results, we successfully fabricated high-density and high-uniformity InAs NWs with quantum size effects on EB-unirradiated SiOx/Si(111). [ABSTRACT FROM AUTHOR]

Realizing an oxide thin film with proper stoichiometry is one of the most challenging objects in materials science. Owing to the growth dynamics as well as kinetics, the physical properties of thin films often differ from their bulk counterparts. Here, we report pulsed laser-deposited thin films of LaBO3 (B = Mn, Fe, Co) grown on a SrTiO3 (001) substrate under various thermodynamic conditions. Structural, magnetic, and optical studies have been carried out. The x-ray diffraction study confirms that an appropriate choice of growth thermodynamics may help one to realize epitaxially grown films on the SrTiO3 substrate with out-of-plane lattice parameters 3.976, 3.984, and 3.825 Å for LaMnO3 (LMO), LaFeO3 (LFO), and LaCoO3 (LCO), respectively. A mixed valence state of Mn2+, 3+, 4+ for LMO, a Fe3+ state for LFO, and a mixed state of Co2+, 3+ for LCO have been confirmed by x-ray photoelectron spectroscopy, which is in good agreement with the Ellingham diagram. The optical study showed a bandgap of 1.2, 2.5, and 1.5 eV for LMO, LFO, and LCO, respectively. Ultraviolet photoelectron spectroscopy (UPS) shows a glimpse of the valence band maximum and Fermi level position. UV, UPS, and photoconductive study simultaneously results in a type II band bending, i.e., staggered type bending is observed at these interfaces. Room temperature weak ferromagnetism along with the insulating nature and a sign of photovoltaic application of these thin films fascinate to carry forward rigorous study from fundamental as well as technological points of view. [ABSTRACT FROM AUTHOR]

The dependence of electron work function, Φ , on the thickness of Ti layers was investigated by making use of the Kelvin method under ambient conditions. Layers were produced by vacuum phase deposition and were analyzed by x-ray photoelectron spectroscopy and transmission electron microscopy. A quantum size effect was revealed finding work function to increase as the layer thickness, z, decreased below 4 nm. The extent of increase, Δ Φ , was understood in terms of a simple particle-in-a-box model arriving at the function Δ Φ = ℏ 2 π 2 / 2 m e z 2 . This equation being free of any adjustable parameter, consisting only of the Planck constant and electron mass, seems to be a reasonable first approximation. [ABSTRACT FROM AUTHOR]

The recent demonstration of the existence of an intimate relationship between the chiral structure of some materials and the spin polarization of electrons transmitted through them, what has been called the chirality-induced spin selectivity (CISS) effect, is sparking interest in many related phenomena. One of the most notorious is the possibility of using magnetic materials to apply enantioselective interactions on chiral molecules and chemical reactions involving them. In this work, x-ray photoelectron spectroscopy has been used to characterize the adsorption and growth kinetics of enantiopure organic molecules on magnetic (Co) and non-magnetic (Cu) substrates. While on these latter, no significant enantiosensitive effects are found, on spin-polarized, in-plane magnetized Co surfaces, the two enantiomers have been found to deposit differently. The observed effects have been interpreted as the result of one of the enantiomers being adsorbed in a transient, weakly bound physisorbed-like state with higher mobility due to limited, spin-selective charge transfer between it and the substrate. The study of these phenomena can provide insight into the fundamental mechanisms responsible for the CISS effect. [ABSTRACT FROM AUTHOR]

The holy grail of achieving efficient operation of infrared (IR) rectennas continues to be the realization of a high performance rectifier. In this paper, we have fabricated metal–insulator–metal (MIM) diodes based on TiO2, ZnO, and NiO thin films using shadow mask evaporation, photolithography, and sputtering. The electron affinities of oxides have been measured by a combination of variable angle spectroscopic ellipsometry and x-ray photoelectron spectroscopy, as well as deduction from the extraction of metal/oxide barrier heights of Fowler–Nordheim tunneling plots. Our results confirm a low value for the electron affinity of NiOx of ∼2.1–2.5 eV, which correlates with the high zero-bias dynamic resistance (RD0) of ∼500 kΩ of an associated MIM diode. These values render NiOx to be unsuitable for use in a rectenna device. Better performance has been observed from diodes based on TiO2 and ZnOx films. The best rectification performance was achieved for a Au/2.6 nm ZnOx/Cr diode, scaled down to 1 μm2 device area, showing a zero-bias dynamic resistance of RD0 = 71 kΩ, zero-bias responsivity β0 = 0.28 A/W, and a coupling efficiency of ηc = 2.4 × 10−5% for rectification at 28.3 THz. The main significance of this study is that it employs a methodology whereby key parameters of the MIM stack are derived from physical measurements, which are then used to assist in the fitting of electrical current–voltage data to produce a reliable appraisal of diode performance in an IR rectenna. [ABSTRACT FROM AUTHOR]

In an interconnected high-vacuum illustration system, the surfaces of p-InGaN/GaN heterostructures grown with integrated metalorganic chemical vapor deposition were treated in O2 gas for different times at room temperature and then transferred to another chamber for fabricating ohmic contacts via sputtering Pd/Pt/Au multi-layers. X-ray photoelectron spectroscopy measurements unveil that the proportions of Ga–O of the treated samples significantly increase compared with that of the as-grown sample, indicating that a thin layer of GaOx forms on the p-InGaN/GaN surface after exposing to oxygen or air atmospheres. Meanwhile, the samples exposed to O2 or air were found to have much higher specific contact resistance, i.e., higher by two orders of magnitude than that of the as-grown sample. The specific contact resistance of the as-grown sample was derived as 9.3 × 10−5 Ω cm2 using the circular transmission line measurement. Furthermore, the Schottky barrier height of the samples was determined from the measured I–V curves with the thermionic field emission model and was revealed to be closely related to surface treatments. Despite the fact that the insulating layer of GaOx was as thin as 1.2–1.4 Å for the samples exposed to oxygen at room temperature, it can act as an extra barrier layer causing significant increase in the specific contact resistance via blocking the tunneling of carriers. Therefore, the effective removal of p-InGaN surface oxide plays a vital role in preparing good ohmic contacts. [ABSTRACT FROM AUTHOR]

Electrical and thermal measurements were conducted during the plasma electrolytic polishing (PEP) of cemented tungsten carbide (WC-Co) materials to characterize energetic aspects of the process in relation to the temporal development of the gaseous layer near the workpiece. The power transferred to the workpiece is determined using a calorimetric probe and employing the time derivative of the temperature curve. It shows distinct heating phases due to the generation of the gaseous layer. At the beginning of the process, a typical power of 367 ± 17 W is transferred to the workpiece of a surface area of 14 cm2. At longer process times, a stabilized gaseous layer limits the power transferred to the workpiece to 183 ± 3 W. In an attempt to describe the heat transferred to the electrolyte, the electrolyte temperature was measured using a thermocouple situated 15 mm away from the workpiece. The local electrolyte temperature increases from 70 to 81 °C for an immersion depth of 20 mm. Moreover, the spatiotemporal development of the electrolyte temperature was obtained by 2D-hydrodynamic modeling using COMSOL Multiphysics®. The modeling results for the local temporal temperature development are in excellent agreement with the experimental values when the turbulent model is applied up to t = 65 s. Afterward, the laminar model leads to a better agreement. Furthermore, line scan x-ray photoelectron spectroscopy revealed that aliphatic carbon was preferentially removed. Only a slight compositional gradient in the vertical direction after the PEP process was observed. [ABSTRACT FROM AUTHOR]

Metal oxide semiconductors constitute a vast group of materials whose physical properties are greatly affected by native defects. For decades, x-ray photoelectron spectroscopy (XPS) has been widely used in defect analysis. However, correct interpretation of XPS results remains a difficult task. In this work, we present a detailed first-principles study on the core-level shift of the most stable and commonly cited crystal imperfections in ZnO, including O and –OH species at the surface with different coverages and bulk defects, including O interstitial (Oi), O vacancy in the +2 charge state (Vo2+), and the neutral vacancy (Vo0). The O1s core level spectrum is simulated and compared with experiments to understand the correlation between local atomic structures and features in the O1s spectrum. In particular, our results indicate that the widely adopted assignment in the defect analysis of ZnO, which links the defect peak in XPS to Vo, the most stable defect, is very likely a misinterpretation. Theoretical analysis indicates that there are no distinguishable XPS features arising from the Vo defect. Furthermore, we show that the commonly observed defect-related peak instead arises due to Oi or specific surface configurations. Given the importance of native defects in materials performance, misinterpretation of XPS results may lead to erroneous conclusions regarding materials properties. This work provides a first-principles basis for the analysis of oxide defects through XPS. [ABSTRACT FROM AUTHOR]

A major roadblock to scalable quantum computing is phase decoherence and energy relaxation caused by qubits interacting with defect-related two-level systems (TLSs). Native oxides present on the surfaces of superconducting metals used in quantum devices are acknowledged to be a source of TLS that decrease qubit coherence times. Reducing microwave loss by "surface engineering" (i.e., replacing the uncontrolled native oxide of superconducting metals with a thin, stable surface with predictable characteristics) can be a key enabler for pushing performance forward with devices of higher intrinsic quality factor. In this work, we present a novel approach to replace the native oxide of niobium (typically formed in an uncontrolled fashion when its pristine surface is exposed to air) with an engineered oxide, using a room-temperature process that leverages accelerated neutral atom beam (ANAB) technology at 300 mm wafer scale. This ANAB is composed of a mixture of argon and oxygen, with tunable energy per atom, which is rastered across the wafer surface. The ANAB-engineered Nb-oxide thickness was found to vary from 2 to 6 nm depending on ANAB process parameters. The modeling of variable-energy x-ray photoelectron spectroscopy data confirms the thickness and compositional control of Nb surface oxide by the ANAB process. These results correlate well with those from transmission electron microscopy and x-ray reflectometry. Since ANAB is broadly applicable to material surfaces, the present study indicates its promise for modification of the surfaces of superconducting quantum circuits to achieve longer coherence times. [ABSTRACT FROM AUTHOR]

Controlled thinning of wide bandgap semiconductors by chemo-mechanical polishing (CMP) and/or reactive ion etching (RIE) has been one of the versatile methods for various optoelectronic applications. The influences of CMP and subsequent wet chemical etching, as well as independent RIE, on the room-temperature photoluminescence lifetime for the near-band-edge emission [ τ PL NBE (RT) ] of O-polarity c-plane ZnO single crystals were examined by using time-resolved photoluminescence measurements. τ PL NBE (RT) decreased from a nanosecond range to a few picoseconds (ps) by a conventional CMP, indicating a generation of high-concentration midgap recombination centers, such as nonradiative recombination centers and deep radiative recombination centers. τ PL NBE (RT) was progressively regained up to 600 ps by a subsequent etching using HCl aqueous solution. However, the recovery saturated at the etching depth of about 200 nm and τ PL NBE (RT) was not restored even after etching by 350 nm. The results indicate the introduction of certain structural deformations during the CMP. Because x-ray diffraction measurement revealed the presence of incoherent surface domains right after the CMP and the HCl etching gave rise to inhomogeneously etched canyons, nonradiative recombination centers, such as dislocations and vacancy clusters, are likely generated by mechanical shear stresses. τ PL NBE (RT) also decreased by the RIE. However, the degradation was less significant than the case for the CMP, because RIE scarcely gives mechanical stresses. Interestingly, τ PL NBE (RT) for the samples etched under higher plasma power was longer than the lower power cases. From the results of x-ray photoelectron spectroscopy measurements, unintentionally deposited oxide films containing Si are proposed to act as an attenuating layer for the introduction of nonradiative recombination centers. [ABSTRACT FROM AUTHOR]

Ferroelectric hafnium-zirconium oxide (HZO) is an excellent candidate for low-power non-volatile memory applications due to its demonstrated ferroelectricity at the nanoscale and compatibility with silicon-based technologies. The interface of HZO in contact with its electrode, typically TiN in a metal–ferroelectric–metal (MFM) capacitor configuration, is of particular interest because factors, such as volume confinement, impurity concentration, interfacial layers, thermal expansion mismatch, and defect trapping, are believed to play a crucial role in the ferroelectric performance of HZO-based devices. Processing variables, such as precursor type, oxygen source, dose duration, and deposition temperature, are known to strongly affect the quality of the oxide–metal interface. However, not many studies have focused on the effect of breaking or maintaining vacuum during MFM deposition. In this study, sequential, no-atmosphere processing (SNAP) is employed to avoid atmospheric exposure, where electrode TiN and ferroelectric HZO are deposited sequentially in the atomic layer deposition chamber without breaking vacuum. The effect of breaking vacuum during the sequential deposition steps is elucidated by fabricating and characterizing MFM capacitors with and without intentional vacuum breaks prior to the deposition of the HZO and top TiN. Using x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS), we reveal that breaking vacuum after bottom TiN electrode deposition leads to interfacial oxidation and increased carbon contamination, which preferentially stabilizes the non-ferroelectric tetragonal phase and lead to diminished remanent polarization. Avoiding carbon impurities and interfacial TiOx at the HZO and TiN interface using SNAP leads to heightened remanent polarization, reduced leakage current density, and elimination of the wake-up effect. Our work highlights the effect of vacuum breaking on the processing-structure-properties of HZO-based capacitors, revealing that maintaining vacuum can significantly improve ferroelectric properties. [ABSTRACT FROM AUTHOR]

With the development of modern industry, the discharge of dye wastewater is increasing year by year, and the damage caused by this wastewater to the ecosystem is often irreversible. Therefore, the research on the harmless treatment of dyes has attracted much attention in recent years. In this paper, commercial titanium dioxide (anatase nanometer titanium dioxide) was heat treated with anhydrous ethanol to synthesize titanium carbide (C/TiO2). Its maximum adsorption capacity for cationic dyes methylene blue (MB) and Rhodamine B is 27.3 and 124.6 mg g−1, respectively, which is much higher than that of pure TiO2. The adsorption kinetics and isotherm model of C/TiO2 were studied and characterized by Brunauer–Emmett–Teller, x-ray photoelectron spectroscopy, x-ray diffraction, Fourier transform infrared spectroscopy, and other methods. The results show that the carbon layer on the surface of C/TiO2 promotes the increase in surface hydroxyl groups, which is the main reason for the increase in MB adsorption. Compared with other adsorbents, C/TiO2 showed excellent reusability. The experimental results of adsorbent regeneration showed that the adsorption rate R% of MB was almost unchanged after three cycles. During the recovery of C/TiO2, the dyes adsorbed on its surface are removed, which solves the problem that the adsorbent cannot degrade dyes simply by adsorption. Additionally, C/TiO2 has a stable adsorption effect, is insensitive to the pH value, has a simple preparation process, and has relatively low raw material prices, making it suitable for large-scale operation. Therefore, it has good commercial prospects in the organic dye industry wastewater treatment. [ABSTRACT FROM AUTHOR]

We report an N2 based annealing treatment to passivate interface traps (Dit) in n- and p-type 4H-SiC. The process has the potential to replace the commonly used hazardous and expensive gas nitric oxide (NO). N2 postoxidation annealing reduces Dit in both the upper and lower halves of the 4H-SiC bandgap, with a greater impact at the valence band edge. N2 annealing at 1500 °C is observed to be more effective in passivating traps and positive fixed charges than NO annealing for p-type devices, whereas for n-type devices, the opposite is true. The breakdown voltages for these devices are found to be lower than that of NO annealed devices. X-ray photoelectron spectroscopy has been performed to estimate the nitrogen areal density at the interface. Dit is measured as a function of nitrogen areal densities in the near interfacial regions for the different processes. Theoretical analysis through density functional theory is consistent with the measured Dit profiles by showing the generation of additional states near the valence band edge due to increased nitrogen concentration. In addition to reporting the effect of N2 annealing on both n- and p-type 4H-SiC, this work correlates the nitrogen areal densities at the interface to the Dit and explains the difference in Dit characteristics with nitrogen areal density between n- and p-type interfaces. [ABSTRACT FROM AUTHOR]

Cubic boron nitride (c-BN), with a small 1.4% lattice mismatch with diamond, presents a heterostructure with multiple opportunities for electronic device applications. However, the formation of c-BN/diamond heterostructures has been limited by the tendency to form hexagonal BN at the interface. In this study, c-BN has been deposited on free standing polycrystalline and single crystal boron-doped diamond substrates via electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD), employing fluorine chemistry. In situ x-ray photoelectron spectroscopy (XPS) is used to characterize the nucleation and growth of boron nitride (BN) films as a function of hydrogen gas flow rates during deposition. The PECVD growth rate of BN was found to increase with increased hydrogen gas flow. In the absence of hydrogen gas flow, the BN layer was reduced in thickness or etched. The XPS results show that an excess of hydrogen gas significantly increases the percent of sp2 bonding, characteristic of hexagonal BN (h-BN), particularly during initial layer growth. Reducing the hydrogen flow, such that hydrogen gas is the limiting reactant, minimizes the sp2 bonding during the nucleation of BN. TEM results indicate the partial coverage of the diamond with thin epitaxial islands of c-BN. The limited hydrogen reaction is found to be a favorable growth environment for c-BN on boron-doped diamond. [ABSTRACT FROM AUTHOR]

The growing demand for improved electrochemical performance in energy storage systems has stimulated research into advanced two-dimensional (2D) materials for electrodes. In this work, we obtain a layered MXene compound by exfoliating a titanium aluminum carbide precursor using tetramethylammonium hydroxide (TMAOH) ions in a full room temperature process followed by manual shaking. The hexagonal crystal structure and composition of the layered materials are characterized using different techniques. X-Ray diffraction shows the formation of 2D nano-sheets before and after the TMAOH treatment via its characteristic (002) diffraction peak, bringing to light an increase in the interlayer spacing after treatment. Scanning electron microscopy images confirm the layered morphology, whose composition is determined by energy dispersive x-ray analysis for the bulk material and by x-ray photoelectron spectroscopy for the surface of the obtained compounds. This study demonstrates a promising route to enhance delamination of this MXene 2D material in a low-cost room-temperature approach. [ABSTRACT FROM AUTHOR]

A highly efficient ternary nanocomposite consisting of multiwalled carbon nanotubes (MWCNTs), graphitic carbon nitride (g-C3N4), and bismuth sulfide (Bi2S3) is developed via a simple one-step hydrothermal route. The structural, morphological, and optical properties of the developed nanocomposites are systematically analyzed using x-ray diffraction, x-ray photoelectron spectroscopy, electron microscopy, UV–vis diffuse reflectance spectroscopy, and Brunauer, Emmett, and Teller analysis. The ternary nanocomposite g-C3N4/Bi2S3/MWCNT-6 wt. % exhibits two times higher photocatalytic performance (99.6%) than g-C3N4/Bi2S3 and g-C3N4/MWCNT binary heterostructures under visible light irradiation within 50 min. The enhanced photocatalytic activity is attributed to the strong absorption of visible light and enhanced charge carriers separation efficiency, high surface area, and synergistic effect of g-C3N4, Bi2S3, and MWCNTs. A reaction mechanism for enhanced photocatalytic performance has also been proposed. The effect of different scavengers is performed to determine the role of the main reactive species responsible for dye degradation, which reveals that electrons are the main reactive species responsible for dye degradation. Moreover, the g-C3N4/Bi2S3/MWCNT ternary photocatalyst maintained excellent stability even after several cycles. Thus, the study offers a promising, stable, highly efficient, and visible-light-driven photocatalyst for dye wastewater purification. [ABSTRACT FROM AUTHOR]

The electrolyte effect has been key to the electrochemical CO2 reduction reaction (CO2RR) and has received extensive attention in recent years. Here we combined atomic force microscopy, quasi-in situ X-ray photoelectron spectroscopy, and in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) to study the effect of iodine anions on Cu-catalyzed CO2RR in the absence or presence of KI in the KHCO3 solution. Our results suggested that iodine adsorption caused coarsening of the Cu surface and altered its intrinsic activity for CO2RR. As the potential of the Cu catalyst became more negative, there was an increase in surface iodine anion concentration ([I−]), which could be connected to the reaction-enhanced adsorption of I− ions accompanying the increase in CO2RR activity. A linear relationship was observed between [I−] and current density. SEIRAS results further suggested that the presence of KI in the electrolyte strengthened the Cu–CO bond and facilitated the hydrogenation process, enhancing the production of CH4. Our results have thus provided insight into the role of halogen anions and aided in the design of an efficient CO2RR process. [ABSTRACT FROM AUTHOR]

Passivation capping that enhances the photoluminescence (PL) of molecular beam epitaxy (MBE)-grown InAs surface quantum dots (SQDs) is realized by ex situ low-temperature atomic layer deposition (ALD)-grown Al2O3. As the Al2O3 cap thickness increased from 2 to 30 nm, the PL intensity was enhanced by 2.7-fold and the blue shift was suppressed. This is in strong contrast to wet chemistry passivation and in situ GaAs capping by MBE, both of which resulted in significant PL blueshift, due to etching in the former, and In/Ga intermixing and strain in the latter. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) reveal that the Al2O3 cap layer mimics the shape of the underlying SQDs. The cross-sectional transmission electron microscopy (TEM) further reveals that the SQD size and shape remained unchanged after Al2O3 capping, which is in strong contrast to MBE-capping. The passivation mechanisms and native oxide reduction by trimethylaluminum (TMA), including self-clean-up reaction through ligand exchange, are discussed based on the results by x-ray photoelectron spectroscopy (XPS). A detailed comparison between Al2O3 and ZnO cap layers reveals the significance of the cap properties on the SQD size/shape and PL blueshift. While the size/shape of SQDs is preserved by Al2O3 capping, the apex is slightly removed by ZnO capping, resulting in a stronger PL blueshift compared to Al2O3. [ABSTRACT FROM AUTHOR]

Here, we report a successful synthesis of single crystals of a topological semimetal (TSM) candidate, PdSn4, using a self-flux route. The synthesized crystal is well characterized through x-ray diffraction (XRD), field emission scanning electron microscopy, and x-ray photoelectron spectroscopy. A detailed Rietveld analysis of the powder XRD pattern of PdSn4 confirmed the same to crystallize in an Aea2 space group instead of reported Ccce. A large magnetoresistance (MR) along with Shubnikov–de Haas (SdH) oscillations have been observed in magneto-transport measurements at 2 K. The presence of weak antilocalization (WAL) effect in the synthesized PdSn4 crystal is confirmed and analyzed using Hikami Larkin Nagaoka formalism, being applied on magnetoconductivity of the same at a low magnetic field. An extended Kohler's rule is implemented on MR data to determine the role of scattering processes and temperature-dependent carrier density on the transport phenomenon in PdSn4. Furthermore, the non-trivial band topology and the presence of edge states are shown through density functional theory-based theoretical calculations. All calculations are performed considering the Aea2 space group symmetry. The calculated Z2 invariants (0; 0 1 0) suggest the presence of weak topological insulating properties in PdSn4. A clear evidence of topological edge states at Γ point is visible in calculated edge states spectra. This is the first report on PdSn4, showing the presence of SdH oscillation in magneto-transport measurements. Also, the presence of a weak insulating phase in PdSn4 is described for the first time on the basis of calculated Z2 invariants. [ABSTRACT FROM AUTHOR]

The optical properties of non-toxic indium phosphide (InP) quantum dots (QDs) are impinged by the existence of characteristic deep trap states. Several surface engineering strategies have been adopted to improve their optical quality, which has promoted the use of InP QDs for various technological applications. An antithetical approach involves the effective utilization of the deep trap states in InP QDs to modulate back electron transfer rates. Here, we explore the influence of the core-size of InP on their In-to-P stoichiometry and charge transfer dynamics when bound to an acceptor molecule, decyl viologen (DV2+). The mechanism of interaction of InP and DV2+ based on the quenching sphere model established the presence of (i) a 1:1 complex of DV2+ bound on InP and (ii) immobile quenchers in the quenching sphere, depending on the concentration of DV2+. While the forward electron transfer rates from photoexcited InP to bound DV2+ does not substantially vary with an increase in core size, the back electron transfer rates are found to be retarded. Findings from inductively coupled plasma-optical emission spectroscopy (ICP-OES) and X-ray photoelectron spectroscopy (XPS) reveal that the In to P ratio is higher for QDs with larger core size, which further brings about increased carrier trapping and a decreased rate of charge recombination. Furthermore, long-lived charge-separated states in DV2+ bound to InP, extending to hundreds of milliseconds, are obtained by varying the number of DV2+ in the quenching sphere of the QDs. [ABSTRACT FROM AUTHOR]

In the present study, soft x-ray optical properties of off-stoichiometric boron carbide thin films are investigated, and the structure and chemical composition of the film is analyzed using angle dependent x-ray reflectivity and x-ray photoelectron spectroscopy techniques. Energy dependent soft x-ray reflectivity measured at a fixed grazing angle of 1.5° is used to determine the optical constants in the boron K edge region by applying the Kramers–Kronig technique. The measured optical constants show near edge fine features corresponding to σ* and π* resonances. The electronic transitions corresponding to σ* resonance cause a 40%–75% increase in the delta value in the above boron K edge region. The π* transitions corresponding to off-stoichiometric nature of the boron carbide are observed in the absorption spectra near ∼192.7 eV. Details of the measured soft x-ray optical properties of the off-stoichiometric boron carbide thin film are discussed. [ABSTRACT FROM AUTHOR]

To understand the roles of Au(III) (hydro-)oxides in promoting plasmon-mediated photoelectrochemical (PMPEC) water-oxidation, we employed in situ microphotoelectrochemical surface-enhanced Raman spectroscopy and ambient-pressure x-ray photoelectron spectroscopy to elucidate the correlations between the amount of surface Au(III) (hydro-)oxides and the photocurrent of PMPEC water-oxidation on Au. By applying preoxidation potentials, we made surface Au(III) (hydro-)oxides on a plasmonic Au photoanode. According to the charge of reductively stripping surface oxygenated species before and after PMPEC water-oxidation, we found that a negative shift of an onset potential, increase in photocurrent, and much less growth of surface (hydro-)oxides were correlated with each other as a result of the increase in the coverage of Au (III) (hydro-)oxides. These results suggest that the surface Au(III) (hydro-)oxides kinetically promoted water-oxidation by restricting the growth of surface (hydro-)oxides. [ABSTRACT FROM AUTHOR]

An AA′3B4O12-type perovskite oxide PbMn3(CrMn3)O12 was synthesized by high-pressure solid-state reactions at 8 GPa and 1373 K. Synchrotron X-ray diffraction shows a cubic crystal structure with the space group Im3¯. The charge states are verified by X-ray photoelectron spectroscopy to be PbMn3+3(Cr3+Mn3+2Mn4+)O12, where the Pb2+ and Mn3+ are 1 : 3 ordered respectively at A and A′ sites, while the Cr3+, Mn3+ and Mn4+ are disorderly distributed at the B site. PbMn3(CrMn3)O12 features a long-range antiferromagnetic order of A′-site Mn3+ spins at about 66 K and a subsequent spin glass transition around 36 K due to the randomly distributed Cr3+, Mn3+, and Mn4+ cations at the B site. This unique stepwise order of A′ and B-site spins indicates weak A′–B site spin interactions, which are dominated by the difference in the B-site Mn3+/Ni2+ and Mn4+ number in the quadruple perovskites AMn3B4O12. [ABSTRACT FROM AUTHOR]

Herein, a series of N-doped Ti3C2/porous g-C3N4 composites are ultrasonically prepared from N-doped Ti3C2 and porous g-C3N4 under N2 atmosphere. The structure, morphology, and optical characteristics of the as-prepared composites are characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, etc. Moreover, photocatalytic measurements show that N-doped Ti3C2 is an excellent modifier for porous g-C3N4 to heighten its photocatalytic activity. Only 44.1% of rhodamine B can be degraded by the photocatalysis of pristine porous g-C3N4, while the photocatalytic degradation ratio of rhodamine B can reach up to 97.5% for the optimal N-doped Ti3C2 loading composites under visible light for 15 min. Moreover, the photocatalytic tests of N2 fixation confirm that the optimal composites show the highest production yield of NH4+ (11.8 μmol gcat−1 h−1), which is 2.11-folds more than that of porous g-C3N4 (5.6 μmol gcat−1 h−1). The reinforced photocatalytic properties are revealed to profit from the more photogenerated electrons and holes' separation, higher ability for light response, and more abundant active sites. This work develops the route for boosting the photocatalytic properties of porous g-C3N4 with N-doped Ti3C2. [ABSTRACT FROM AUTHOR]

Two new heteroleptic indium aminothiolate compounds [InClSC2H4N(Me)SC2H4]3[1] and [InSC2H4N(Me)SC2H4(C8H5F3NO)] [2] were synthesized by in situ salt metathesis reaction involving indium trichloride, aminothiol, and N,O-β-heteroarylalkenol ligands. The complexes were subsequently purified and thoroughly characterized by nuclear magnetic resonance (NMR) analysis, elemental studies, mass spectroscopy, and X-ray diffraction single crystal analysis that showed a trigonal bipyramidal coordination of In(III) in both complexes. Thermogravimetric analysis of [1] revealed a multistep decomposition pathway and the formation of In2S3 at 350 °C, which differed from the pattern of [2] due to the lower thermal stability of [1]. Compound [2] exhibited a three-step decomposition process, resulting in the formation of In2S3 at 300 °C. The Chemical Vapor Deposition (CVD) experiment involving compound [2] was conducted on the FTO substrate, resulting in the production of singular-phase In2S3 deposits. A comprehensive characterization of these deposits, including crystal structure analysis via X-ray diffraction (XRD), and surface topography examination through scanning electron microscopy (SEM) has been completed. The presence of In–S units was also supported by the Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS) of the as-deposited films. Moreover, the electronic structure and thermal properties of compound [2] were investigated through DFT calculations. Electron density localization analysis revealed that the highest occupied molecular orbital (HOMO) exhibited dense concentration at the aminothiolate moiety of the complex, while the lowest unoccupied molecular orbital (LUMO) predominantly resided at the N,O-β-heteroarylalkenolate ligand. Furthermore, our computational investigation has validated the formation of indium sulfide by elucidating an intermediate state, effectively identified through EI-MS analysis, as one of the plausible pathways for obtaining In2S3. This intermediate state comprises the aminothiolate ligand (LNS) coordinated with indium metal. [ABSTRACT FROM AUTHOR]

This study reports a facile and reliable operando X‐ray photoelectron spectroscopy (XPS) system for the characterization of the chemical state and electronic structure during Li‐plating/stripping in all‐solid‐state batteries (ASSBs). The measurement conditions (including manufacturing an in situ sample holder) and experimental parameters have been optimized through experimentation. The proposed system accurately defines the status of every metal interlayer component during real‐time battery operation (with simultaneous Li+‐ion in/out migration) under a repeating Li‐plating/stripping process. Moreover, it enables elucidation of ambiguous reaction mechanisms depending on the battery performance, such as the interlayer‐material effect on the efficiency and reversibility of the Li‐plating/stripping process, and changes in the oxygen‐containing bonds due to reaction with Li. The significance of the developed system is further validated by the usefulness and reliability of the valence band structure as a criterion for the analysis of lithium‐metal alloy formation and the progress of de‐alloying reactions. [ABSTRACT FROM AUTHOR]

The conversion of CO 2 into synthetic natural gas offers a promising approach for the long-term storage of renewable energy, addressing the challenge of its intermittent supply. This study successfully developed a catalyst comprised of LaNiO 3 supported by CeO 2 , synthesized via a citric acid-aided impregnation method. This catalyst demonstrated efficiency and stability as a precursor for the CO 2 methanation reaction. Upon reduction, it transforms into a Ni–La 2 O 3 /CeO 2 configuration, featuring dispersed Ni nanoparticles. Characterization through hydrogen temperature-programmed reduction (H 2 -TPR) revealed that this catalyst exhibits enhanced reducibility and smaller particle sizes, which promote hydrogen activation at lower temperatures. X-ray photoelectron spectroscopy (XPS) analysis further clarified that the increased catalytic activity results from electron transfer interactions between Ni, CeO 2 , and La 2 O 3. Moreover, the catalyst displayed an augmented count of weak to medium basic sites, which, along with improved hydrogen activation, elevated the CO 2 conversion rate to 83.8% within the kinetic control region. The collaborative effect of Ni, La 2 O 3 , and CeO 2 substantially outperformed the conventional Ni/CeO 2 catalyst in CO 2 methanation efficiency. Additionally, in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) analysis revealed that the methanation process predominantly follows the HCOO* pathway. Notably, the LaNiO 3 /CeO 2 catalyst exceeded the performance of Ni–La/CeO 2 in CO 2 adsorption, HCOO* intermediate decomposition, and CHO* conversion, significantly enhancing low-temperature methanation activity. [Display omitted] • LaNiO 3 /CeO 2 -derived catalyst with high CO 2 to CH 4 conversion and stability. • La 2 O 3 -modified surfaces contributed to the high ability for CO 2 chemisorption and activation. • Key reaction intermediates are identified by in-situ DRIFTS analysis. • CO 2 methanation produces CH 4 via the HCOO* pathway. [ABSTRACT FROM AUTHOR]