X-ray Photoelectron Spectroscopy Spectra Research Articles

Enhance photocatalytic CO2 reduction and biomass selective oxidation via sulfur vacancy-enriched S-scheme heterojunction of MoS2@GCN

Photocatalytic CO2 reduction and biomass selective oxidation have considerable practical implications in addressing environmental challenges. However, developing efficient photocatalyst is the key to realize the mass-market applications. Herein, an MoS2@GCN S-scheme heterojunction, rich in sulfur vacancies (Sv), was fabricated by a dicyandiamide-blowing and calcination strategy using NH4Cl as the gas template. With the synergistic effects of Sv and the S-scheme charge migration mechanism, the 30%-Sv-MoS2@GCN demonstrated exceptional performance, showcasing a CO evolution rate of 68.3 μmol g−1 h−1 and a xylonic acid yield of 64.2%, without using any sacrificial agents. The formation of Sv was confirmed through electron paramagnetic resonance (EPR) analysis. The S-scheme charge transfer mechanism of the Sv-MoS2@GCN heterojunction was verified by in-situ X-ray photoelectron spectroscopy (XPS) spectra, EPR analysis, and density functional theory (DFT) calculations. This study establishes a framework for enhancing photocatalytic CO2 reduction and biomass selective oxidation by regulating charge transfer through sensible structural design.

Light-Mediated Contact Printing of Phosphorus Species onto Silicon Using Carbene-Based Molecular Layers.

The ability to deposit pattern-specific molecular layers onto silicon with either regional p-/n-doping properties or that act as chemoselective resists for area-selective deposition is highly sought after in the bottom-up manufacturing of microelectronics. In this study, we demonstrate a simple protocol for the covalent attachment and patterning of a phosphorus-based dopant precursor onto silicon(100) functionalized with reactive carbene species. This method relies on selective surface reactions, which provide terminal functionalities that can be photochemically modified via ultraviolet-assisted contact printing between the carbene-functionalized substrate and an elastomeric stamp inked with the inorganic dopant precursor. X-ray photoelectron spectroscopy (XPS) analysis combined with scanning electron microscopy (SEM) imaging was used to characterize the molecule attachment and patterning ability of this technique. XPS spectra are indicative of the covalent bonding between phosphorus-containing molecules and the functionalized surface after both bulk solution-phase reaction and photochemical printing. SEM analysis of the corresponding printed features demonstrates the effective transfer of the phosphorus species in a patterned orientation matching that of the stamp pattern. This simple approach to patterning dopant precursors has the potential to inform the continued refinement of thin-film electronic, photonic, and quantum device manufacturing.

Synthesis of Green Carbon Dots from Nephelium Lappaceum L. Seeds

In this study, rambutan (Nephelium Lappaceum L.) seeds were used to fabricate green carbon dots (gCDs) by employing a hydrothermal process. The synthesized CDs were evaluated using Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) for the structural properties as well as UV-Vis and fluorescence spectrophotometry for the optical properties. UV-Vis examination revealed that the produced gCDs showed emission-dependent photoluminescence excitation, with two absorption peaks at 265 nm and 330 nm. The presence of functional groups and chemical composition such as C=C, C=O, -COOH, and -OH on the surface of gCDs was confirmed by the results of FTIR and XPS spectra. Consequently, gCDs present several opportunities for exploration in a range of applications.

Surface science insight note: Imaging X‐ray photoelectron spectroscopy

Quantification of X‐ray photoelectron spectroscopy (XPS) data is often limited by the heterogeneous nature of the material surface. However, it is often the case that heterogeneous material contains areas within the analyzed area that are effectively homogeneous. In this Insight note, concepts, and methods used to analyze both XPS data are presented to extract both spatial and spectral information from heterogeneous surfaces. These concepts and methods are applied to a specific material surface that contains three chemical compounds separated spatially. The analysis entails converting XPS image data to spectral data and is designed to highlight the potential of XPS imaging in revealing compositional information correlation with spatial information. Properties of algorithms used to evaluate XPS images and spectra are described to outline their application to image data. A case study of an imaging XPS data set is presented that demonstrates how poor signal‐to‐noise images, where the signal is recorded for 4 s per image, are still open to analysis yielding useful information. Ultimately, the methods presented here will aid in interpreting complex XPS data obtained from spatially complex materials often obtained during extensive cycling, such as conventional or electrocatalysts.

Synergistic effects of La-doping on ZnO nanostructured photocatalysts for enhanced MB dye degradation

In this work, we present the design and characterization of pristine and La-doped ZnO photocatalysts, prepared via a facile co-precipitation technique. A comprehensive range of characterization techniques was employed to analyze the physicochemical properties of these synthesized nanostructured photocatalysts. The slight shift in the position of peaks in the X-ray diffraction (XRD) pattern confirms successful doping (La3+) of ZnO. Additionally, the identified wurtzite phase further validates the presence of ZnO nanostructures. Subsequent photocatalytic investigations were conducted using model solutions of water and methylene blue (MB) dyes under solar irradiation, meticulously comparing the performance of pure ZnO with La3+ doped ZnO. Over the time span of 90 min, the 5 % La-doped ZnO photocatalysts exhibited an impressive 98 % degradation efficiency for MB dye, surpassing the performance of the pristine ZnO counterpart (0 % La), which achieved only 51 % degradation. This emphasizes the pronounced enhancement resulting from the incorporation of La ions. The photoluminescence (PL) spectra insights with 5 % La3+doping exhibit significant quenching, caused by the suppression of charge carrier recombination, which enhances the photocatalyst's charge transport. X-ray photoelectron spectroscopy (XPS) spectra provided crucial insights into the elemental composition and chemical states of the 5 % La3+ doped ZnO nanostructures. Through systematic reusability assessments, it was established that the 5 % La-doped ZnO photocatalysts maintain their efficiency for up to four cycles, without displaying a significant reduction in removal efficacy. This emphasizes the inherent reliability and robustness of the developed photocatalysts.

Hydrated eutectic electrolyte promotes the preferential growth of Zn (0 0 2) plane and suppresses side reaction for high-stability zinc anodes

Using deep eutectic solvent (DES) electrolytes is an efficient way to suppress the Zn dendrite growth and the side reactions resulting from the high activity of H2O in aqueous zinc-ion batteries (ZIBs). However, most DESs consist of expensive/explosive zinc salts or flammable/toxic organic ligands, which hinders their practical application in ZIBs. Herein, a low-cost and high-safety hydrated eutectic electrolyte based on ZnCl2, urea, and a small amount of H2O is prepared. Due to the low content of H2O and the strong intermolecular interaction between urea and H2O, the activity of H2O is greatly restricted and therefore H2O-induced side reactions are improved. In addition, X-ray photoelectron spectroscopy spectra and density functional theory calculations reveal that the adsorption of urea molecules on the zinc surface forms an organic protective layer, which can induce the preferential growth of the Zn (0 0 2) plane. As a result, with the optimal electrolyte, the Zn||Zn symmetric cell shows a long cyclic life of 1200 h, and the Zn||Cu half-cell delivers a high average Coulombic efficiency of 99.7 % for 2500 cycles. Meanwhile, the Zn||Bi2Te3 and Zn||polyaniline full cells with DES exhibit improved cycling performances compared to those using traditional ZnSO4 electrolyte. This work offers a new perspective to explore low-cost, non-toxic, and high-security DESs for ZIBs.

A self-assembly BiOI/Bi4O5Br2 microcluster and its efficiently visible-light-induced photocatalytic degradation of methylparaben

Herein, we developed a self-assembly heterostructured BiOI/Bi4O5Br2 microcluster with the hydrothermal method. Catalysts were mainly characterized by powder X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscope, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and diffuse reflectance spectra. The results showed that due to charge induction, BiOI nanosheets were successfully self-assembled and deposited on Bi4O5Br2, forming a unique heterojunction and achieving strong transient photocurrent response. Performances of catalysts were tested and effects of different initial concentrations of the Methylparaben (MPB), catalyst dosage, initial pH and total organic carbon (TOC) conversion were studied. Results reveal that catalytic activity increased with lower initial concentration of MPB and the best dosage of catalyst is 0.5 g·L-1. The BiOI/Bi4O5Br2 microcluster exhibits excellent photocatalytic activity under visible-light irradiation, which can degrade 97% MPB in 2 h and the TOC value is only 20% of the original. The catalytic degradation process conforms to pseudo-first-order kinetics with a rate constant of 0.030 min-1. The results of detailed active species detection indicate that the photogenerated holes and •O2− radicals play the main role in the photocatalytic system. In addition, photoelectrochemical measurements reveal that the excellent strengthened photocatalytic activity is due to the high separation and transfer efficiency derived from the heterostructure.

MOF-derived MnCe3.67C6Permeable microflower: A robust electrocatalyst for oxygen evolution reaction

To enhance the accessibility of hydrogen fuel production, there is a pressing need for the development of efficient catalysts possessing abundant catalytic active sites, robust stability, and a substantial surface area conducive to both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In this study, we present a novel electrocatalyst derived from a metal-organic framework (MOF) precursor, specifically MnCe3.67C6, synthesized through a cost-effective and straightforward pyrolysis process. This process involves the transformation of carefully designed porous spongy conjoined tapeworm like morphology at 973.15 K carburized temperature and which transform into conjoined nanowires when carburization temperature increases from 1073.15 to 1273.15 K into aggregated nanospheres, with the MOF serving as a carbon template. The structural, morphological, and compositional characteristics of the resulting MnCe3.67C6 catalyst were thoroughly investigated using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Remarkably, the MnCe3.67C6 catalyst exhibits outstanding OER activity, manifesting a significantly reduced potential of 231 mV at current density of 10 mAcm−2 in alkaline media, thereby facilitating efficient charge transfer. Furthermore, the fabricated MnCe3.67C6-700 electrocatalyst demonstrates a decreased Tafel slope of 68mVdec−1, indicative of a favorable kinetic mechanism for the resultant material. The electrochemical active surface increases considerably after fabrication of composite MnCe3.67C6-700 (Cdl = 77 mFcm−2) as compared to Mn–Ce/MOF (Cdl = 34 mFcm−2). Moreover, the higher OER activity is also complemented with extraordinary stability of MnCe3.67C6-700 that is capable of performing oxygen evolution reaction for more than 150 h, making it attractive candidate for the commercial utilization. Notably, the enhanced catalytic performance of MnCe3.67C6 can be attributed primarily to the well-dispersed cerium on the carbon surface, which provides an enlarged active surface area replete with catalytic sites, as well as the dynamic charge transfer of electrons depicted in XPS spectrum, thereby enhancing electrochemical properties and paving the way for future applications.

Fabrication of high-performance polyimide films by tailoring coordination bond and chain rigidity

Coordination bonds and chain rigidities play severe roles in crystalline structure and property of polyimides (PIs). This study developed various polyimides with metal-diimine coordination bonds and varying chain rigidities. How coordination bonds and chain stiffness affect the semi-crystalline structure of polyimide films was investigated. Results from Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra confirmed the successful synthesis of coordinated polyimide films. Wide-angle diffraction (WAXD) results revealed that the crystallization behavior of PIs with flexible chains is significantly affected by additional coordination bonds, while the crystallization of PIs with rigid structures is primarily influenced by the chain rigidities. Compared to coordinated PIs with amorphous structure, PIs with both coordination bonds and semi-crystalline structures exhibited enhanced heat resistance, crystallinity, and dimensional stability. Notably, the coordinated PI-BP-Cu film with the highest chain rigidity in this study demonstrated excellent mechanical properties, with a tensile strength of 280 MPa, initial modulus of 5.7 GPa, and outstanding dimensional stability, characterized by a linear thermal expansion coefficient of 8.9 ppm/K (40–300 °C). These findings significantly enhance its suitability for use in metal/non-metal bonding composite materials.

Outstanding photocatalytic activity of a mechano-thermally synthesized Z-scheme BiFeO3- Fe2O3 heterostructure

In this study, α-Bi2O3 and α-Fe2O3 powder mixtures experienced a novel mechano-thermal procedure, which includes high-energy ball milling followed by heat treatment, resulting in the successful synthesis of a BiFeO3-Fe2O3 nanocomposite. Simultaneous thermal analysis (STA) and X-ray diffraction (XRD) showed that the formation and characteristics of BiFeO3-Fe2O3 nanocomposite are greatly influenced by the milling process, heat-treatment temperature, and the α-Bi2O3:α-Fe2O3 molar ratio. X-ray photoelectron spectroscopy (XPS) spectra confirmed the presence of Bi, Fe, and O, indicating the formation of the BiFeO3 phase. Field emission scanning electron microscopy (FESEM) analysis showed the development of plate-like microstructures in the BiFeO3 phase with an average thickness of 88 nm. Diffuse reflectance spectroscopy (DRS) indicated that the 20 h-milled nanocomposite with a molar ratio of α-Bi2O3:α-Fe2O3 (1:3) exhibited the lowest band gap of 2.38 eV after heat treatment at 750 °C. The reduction in photoluminescence (PL) peaks and increase in photocurrent in the above sample suggested a decrease in charge carrier recombination rate, leading to high photocatalytic activity of 85 and 42% for methylene blue (MB) and methyl orange (MO) degradation, respectively. The effect of various pH levels on the photocatalytic activity of both dyes was examined, with MO degrading by 94% in an acidic environment after 300 min of visible light exposure, while MB experienced similar degradation in an alkaline setting. The kinetics and mechanism of photocatalytic degradation were extensively studied using the Langmuir-Hinshelwood (L-H) model, revealing the significant role of hydroxyl radicals in photodegradation. A Z-scheme mechanism for charge transfer in the nanocomposite was postulated, drawing upon radical scavenging and Mott-Schottky experiments. The prepared photocatalyst showed excellent stability and reusability following a cyclic experiment.

Investigations of In2O3 Added SiC Semiconductive Thin Films and Manufacture of a Heterojunction Diode

This study involved direct doping of In2O3 into silicon carbide (SiC) powder, resulting in 8.0 at% In-doped SiC powder. Subsequently, heating at 500 °C was performed to form a target, followed by the utilization of electron beam (e-beam) technology to deposit the In-doped SiC thin films with the thickness of approximately 189.8 nm. The first breakthrough of this research was the successful deposition of using e-beam technology. The second breakthrough involved utilizing various tools to analyze the physical and electrical properties of In-doped SiC thin films. Hall effect measurement was used to measure the resistivity, mobility, and carrier concentration and confirm its n-type semiconductor nature. The uniform dispersion of In ions in SiC was as confirmed by electron microscopy energy-dispersive spectroscopy and secondary ion mass spectrometry analyses. The Tauc Plot method was employed to determine the Eg values of pure SiC and In-doped SiC thin films. Semiconductor parameter analyzer was used to measure the conductivity and the I-V characteristics of devices in In-doped SiC thin films. Furthermore, the third finding demonstrated that In2O3-doped SiC thin films exhibited remarkable current density. X-ray photoelectron spectroscopy and Gaussian-resolved spectra further confirmed a significant relationship between conductivity and oxygen vacancy concentration. Lastly, depositing these In-doped SiC thin films onto p-type silicon substrates etched with buffered oxide etchant resulted in the formation of heterojunction p-n junction. This junction exhibited the rectifying characteristics of a diode, with sample current values in the vicinity of 102 mA, breakdown voltage at approximately −5.23 V, and open-circuit voltage around 1.56 V. This underscores the potential of In-doped SiC thin films for various semiconductor devices.

NH3-probe X-ray photoelectron spectroscopy method to characterize solid acidity of clay minerals

Accurate determination of solid acidity is essential for evaluating the catalytic activity of clay minerals. However, the conventional Fourier-transform infrared (FTIR) method using NH3 as the probe encounters challenges in measuring the solid acidity owing to the presence of water on the surface or within interlayer spaces of clay minerals as well as the influence of environmental water during the detection process. To mitigate water interference, a NH3-probe X-ray photoelectron spectroscopy (XPS) approach was adopted as an alternative to the FTIR method for the identification and semi-quantification of solid acidity of clay minerals. Following NH3 adsorption, the types of solid acid sites in clay minerals were identified through the chemical shift in N1s XPS spectra. The ratio of Brønsted and Lewis acid sites in a given sample and the relative concentration of acid sites across different samples were determined by examining the specific N1s peak area ratio. According to the XPS data, the ratios of Brønsted and Lewis acid sites in Ca-montmorillonite (SAz-2) and Na-montmorillonite (SWy-2) were nearly 1:1, whereas that for the illite–smectite mixed-layer mineral (ISCz-1) was 4. The acid site contents in SAz-2 were more than twice those of SWy-2. This work highlights the promising application prospects of the NH3-probe XPS method in solid acidity investigations of clay minerals.

Experiment-Driven Atomistic Materials Modeling: A Case Study Combining X-Ray Photoelectron Spectroscopy and Machine Learning Potentials to Infer the Structure of Oxygen-Rich Amorphous Carbon.

An important yet challenging aspect of atomistic materials modeling is reconciling experimental and computational results. Conventional approaches involve generating numerous configurations through molecular dynamics or Monte Carlo structure optimization and selecting the one with the closest match to experiment. However, this inefficient process is not guaranteed to succeed. We introduce a general method to combine atomistic machine learning (ML) with experimental observables that produces atomistic structures compatible with experiment by design. We use this approach in combination with grand-canonical Monte Carlo within a modified Hamiltonian formalism, to generate configurations that agree with experimental data and are chemically sound (low in energy). We apply our approach to understand the atomistic structure of oxygenated amorphous carbon (a-COx), an intriguing carbon-based material, to answer the question of how much oxygen can be added to carbon before it fully decomposes into CO and CO2. Utilizing an ML-based X-ray photoelectron spectroscopy (XPS) model trained from GW and density functional theory (DFT) data, in conjunction with an ML interatomic potential, we identify a-COx structures compliant with experimental XPS predictions that are also energetically favorable with respect to DFT. Employing a network analysis, we accurately deconvolve the XPS spectrum into motif contributions, both revealing the inaccuracies inherent to experimental XPS interpretation and granting us atomistic insight into the structure of a-COx. This method generalizes to multiple experimental observables and allows for the elucidation of the atomistic structure of materials directly from experimental data, thereby enabling experiment-driven materials modeling with a degree of realism previously out of reach.

Enhancing sp3 content in diamond-like carbon thin film electrodes by pulsed laser annealing for durable charge storage performance

In this work, diamond-like carbon (DLC) thin film electrodes were grown on Si substrate by pulsed laser deposition (PLD) technique, and the implication of pulsed laser annealing (PLA) treatment on their electrochemical supercapacitor performance was examined by three electrode systems in 1 M Na2SO4 electrolyte solutions. The SEM micrographs exhibit a sheet-like wrinkled surface of DLC film on Si which later transformed into tiny hierarchical heap-like structures with enhanced surface roughness. The Raman spectra confirm signature of the D and G peaks of pristine DLC film at ∼1352 cm−1 (1356 cm−1 after PLA) and 1591 cm−1 (1589 cm−1 after PLA), and appearance of minor T2g (diamond) (1332 cm−1) peaks with an increment of the sp3 content after PLA treatment. The X-ray photoelectron spectroscopy (XPS) spectra were deconvoluted into three different contributions CC (sp2), CC (sp3), and CO, and their sp3 percentages were estimated ∼48.9 %, and 64.7 % before and after annealing. The area under cyclic voltammetry (CV) curve and galvanostatic charging discharging (GCD) performance of PLA-treated DLC film were improved and the highest areal-specific capacitance was obtained to be ∼48.25 mF/cm2 for scan rate of 5 mV/s and 36.01 mF/cm2 for current density of 2 mA/cm2, respectively. Excellent charging discharging cyclic stability of PLA treated electrode was observed over 5000 cycles, and Coulombic efficiency and capacitance retention were determined to be ∼93.5 % and ∼ 97.3 %, respectively. The electrochemical impedance spectroscopy (EIS) was performed to obtain the Nyquist plot (Z′vs.Z′′) of both electrodes before and after the stability test, and a small degradation in impedance was observed. The Nyquist plots were fitted with the well-known Randles equivalent circuit model Rs(Cdl(RctZw)) and substantial curtailment of Warburg resistance (Zw) in PLA-induced DLC electrode signifies the dominance of the diffusion-controlled region in the charging-discharging process. Minor changes in the Nyquist plot before and after the stability test manifest the enduring charge kinetics of both electrodes and PLA-treated DLC exhibits better cyclic stability. PLA techniques have a great impact on upgrading the areal-specific capacitance, capacitance retention with high Coulombic efficiency, and stability with negligible impedance loss of the DLC film electrodes.

Reduction of graphene oxide film on glass substrate using argon ion beam irradiation: A systematic study with X-ray photoelectron spectroscopy analysis

In our research, we explored a novel and eco-friendly method of utilizing argon ion beam irradiation to thin down graphene oxide (GO) films on glass substrates, aiming to enhance their mechanical, electrical, and optical properties. By employing high-energy argon ions, we developed a groundbreaking, environmentally conscious technique that not only permits micro-patterning directly on GO films but also facilitates concurrent material characterization. Varying the energy levels (1000, 2000, and 3000 eV) and exposure times (0 to 80 s, in 20-second increments), we meticulously examined the impact on carbon and oxygen atomic ratios of the GO using X-ray photoelectron spectroscopy (XPS) for in-depth analysis. Our findings revealed that increasing the argon ion beam energy to 2000 eV and extending the irradiation time significantly reduced oxygen content while increasing the carbon atomic ratio, indicating effective GO surface reduction. However, further increasing the energy to 3000 eV resulted in a slight increase in oxygen content and a decrease in the carbon atomic ratio compared to the energy 2000 eV, suggesting a decrease in reduction efficacy. This method's simplicity, eco-friendliness, and precision mark a significant advancement over traditional chemical reduction methods, offering a solid understanding of high-energy argon ion beam irradiation's effectiveness in GO reduction. Our comprehensive analysis, including survey and high-resolution C 1s and O 1s XPS spectra, highlights the surface chemistry modifications induced by this treatment, demonstrating the versatility of argon ion beam irradiation in producing reduced graphene oxide (rGO) for various applications.

Growth of β-Ga2O3 nanostructures by thermal oxidation of GaN-on-sapphire for optoelectronic devices applications

Heterostructures of wide-bandgap semiconductors, like β-Ga2O3/ GaN, are being used in many high-power, high-frequency electronic and optoelectronic devices. This paper presents the growth of β-Ga2O3 thin film and nanostructures by thermally oxidizing (at 1000 °C) the planar and nano-structured GaN surfaces respectively. The nano-structures of GaN (having 300–500 nm long vertical nano-kinks) are fabricated by metal-assisted chemical etching of GaN surface for 1–2 hours. The thermally grown β-Ga2O3 samples are polycrystalline. The chemical analysis of the samples using X-ray photoelectron spectroscopy (XPS) showed enhancement of Ga-O peak intensity (at 20.21–20.3 eV) at the expense of the Ga-N peak intensity (at 19.2–19.7 eV) in the thermal oxidation process. The O1s XPS spectra of the oxidized samples exhibited prominent signature of O2- ions (530.7–530.9 eV) representing the formation of Ga2O3 with presence of adsorbed hydroxyl group at the surface (532.2 – 532.4 eV). The valance band XPS spectra disclosed the formation of an additional Ga(4 s)–O(2p) hybridization energy state, and the valence band maxima increased from 2.3 eV to 3.25 eV. The Raman spectra of the oxidized samples exhibited multiple Ag and Bg vibrational modes of β-Ga2O3 along with intense E2(high), A1(LO) modes of GaN. The time-resolved photoluminescence spectra of the samples demonstrated fast transition of charge carriers from excited state to ground state with 460–820 pico-seconds average career lifetime.

Atom-Scaled Hafnium Doping for Strengthening the Germanium Oxide Interfacial Layer of The Gate Stack of Germanium P-Type Metal-Oxide-Semiconductor Field Effect Transistor

We have developed a method that uses a half-cycle Hf precursor adsorption to subtly dope GeO2 IL of the Hf-based gate stack through in situ plasma-enhanced atomic layer deposition. This technique can effectively reduce GeO vaporization and improve the thermal stability of the GeO2 layer. Our results indicated that the accumulation capacitance (Cacc) undergoing higher temperatures showed no noticeable increase in the capacitance-voltage (CV) curves once Hf was delicately introduced into the GeO2 layer. According to the Ge 3d spectra of X-ray photoelectron spectroscopy, we found that the IL had a signal from extra Hf-O bonds; thus, we conclude GeO evaporation can be suppressed substantially by Hf incorporation. As a result, adding metal into GeOx IL to form HfGeOx achieved a remarkably low leakage current of 9 × 10−5 A cm−2 and the lowest interface trap density (Dit) of approximately 2 × 1011 eV−1 cm−2 at 500 °C of PMA. In addition, applying this gate stack structure to device fabrication significantly reduced the leakage current of the off-state and improved the effective peak hole mobility.

Structural, electronic, and optical properties of 6H-SiC layers synthesized by implantation of carbon ions into silicon

Systematic studies of the gradual fabrication by means of carbon ion-implantation of high-quality 6H-SiC layers on silicon surfaces have been carried out. The fluence of carbon ions varied from 5 × 1015 cm−2 to 1017 cm−2. Results of first-principle calculations, X-ray diffraction (XRD), and Raman spectroscopy demonstrate the amorphization of silicon substrate without any tendency to the segregation of carbon in the samples synthesized at low fluencies. The formation of a SiO2-like structure at this stage was also detected. X-ray photoelectron spectroscopy (XPS), XRD, and Raman spectroscopy demonstrate that an increase in carbon content at 1017 cm−2 fluence leads to the growth of 6H-SiC films on the surface of the amorphous silicon substrate. Atomic force microscopy (AFM) data obtained also demonstrates the decreasing of surface roughens after the formation of SiC film. XPS and Raman spectra suggest that excessive carbon content leaves the SiC matrix via the formation of an insignificant amount of partially oxidized carbon nanostructures. Optical measurements also support the claim of high-quality 6H-SiC film formation in the samples synthesized at 1017 cm−2 fluence and demonstrate the absence of any detectable contribution of nanostructures formed from excessive carbon on the optical properties of the material under study.

Efficient green light-emitting diodes based on alloy quantum dots with an organic/inorganic hybrid surface passivation

As we know, the ligands on the surface of core/shell structured quantum dots (QDs) play an important role. They not only bind with metal ions to passivate surface defects but also have a great influence on colloidal stability. All-organic or all-inorganic ligands afford QDs with some disadvantages such as low conductivity, poor dispersibility and undesirable stability. By combining with the advantages of organic and inorganic ligands, herein, we achieve an organic/inorganic hybrid surface passivation through exchanging partial oleic acid ligands with chlorine ions (Cl−), affording QD with a core/shell structure of CdZnSe/ZnSe/ZnS/OACl. It exhibits an excellent nanostructure with a mean size of around 11.6 nm. According to X-ray photoelectron spectroscopy (XPS) spectra, around 30% oleid acid ligands are removed by Cl−, resulting in the hybrid surface passivation. The CdZnSe/ZnSe/ZnS/OACl QD exhibit an efficient green emission at the wavelength of around 535 nm with a quantum yield of over 90%. The QD light-emitting diode (QLED) based on CdZnSe/ZnSe/ZnS/OACl exhibits a peak EQE of 15.6% and a brightness of over 1.1 × 105 cd m−2 at 6 V, corresponding to an efficient green emitting device. Therefore, we believe that the hybrid surface passivation could provid a reliable avenue to efficient QD materials.

XPS Study on the determination of binding energies in high-purity TiO2 nanoparticles

This study focuses on the precise determination of the binding energies of high-purity TiO2 nano-particles, using X-ray photoelectron spectroscopy (XPS). TiO2, an essential ceramic in high-tech sectors such as electronics, aerospace and photocatalysis, was analyzed in its pure state (99.5%) directly as received from the supplier, without previous alterations. XPS spectra revealed typical bond energy peaks for Ti at 458.42 eV and 464.13 eV, corresponding to Ti2p3/2 and Ti2p1/2 levels respectively, with a difference of 5.71 eV, validating the expected electron structure for Ti in TiO2. Additionally, peaks were identified at 457.36 eV and 463.36 eV, attributable to Ti3+, present in a Ti3O5 phase, as confirmed by X-ray diffraction (XRD) analysis. The mid-height width (FWHM) of the main Ti4+ peaks, ranging from 1.08 to 1.87 eV, and 0.96 eV for the Ti3+ peaks, highlights the homogeneity and exceptional purity of the sample. These findings not only corroborate the high quality of TiO2, but also provide a crucial benchmark for the scientific community, facilitating de-tailed comparisons with other samples and encouraging the development of innovative processes and materials. This study underscores the value of the XPS technique in the characterization of advanced ceramic materials and sets a standard for future research.