High-resolution X-ray Photoelectron Spectroscopy Research Articles

Improvement of electrical performance using PtSe2/PtTe2 edge contact synthesized by molecular beam epitaxy

One-dimensional (1D) edge contact is considered critical to reducing contact resistance between two-dimensional transition-metal dichalcogenides (TMDs) and contact metal and overcoming surface contact effects, such as surface damage and orbital hybridization. Although several studies have investigated edge contact, some problems such as inevitable etching damage and a limited area persist. Herein, a tellurization method is applied to a specific lateral region to fabricate PtTe2/PtSe2/PtTe2 edge-contact field-effect transistors (FETs) without etching damage. High-resolution X-ray photoelectron spectroscopy and Raman spectroscopy are used to verify tellurization completion, which is evidenced by the complete transformation of PtSe2 to PtTe2 by the substitution of Se atoms with evaporated Te atoms. Furthermore, tellurization is applied to a specific lateral region by utilizing the hexagonal boron nitride to block the interdiffusion of evaporated Te atoms, which is confirmed by Raman spectroscopy and cross-sectional annular dark-field scanning transmission electron microscopy. Finally, the 1D edge-contact FETs fabricated by tellurization demonstrate a higher on–off ratio and carrier mobility than the surface-contact FET. Therefore, this method can be applied to various FETs based on TMDs for improving electrical performance through a reduction in contact resistance.

Lifetime effects and satellites in the photoelectron spectrum of tungsten metal

Tungsten is an important and versatile transition metal and has a firm place at the heart of many technologies. A popular experimental technique for the characterisation of tungsten and tungsten-based compounds is X-ray photoelectron spectroscopy (XPS), which enables the assessment of chemical states and electronic structure through the collection of core level and valence band spectra. However, in the case of metallic tungsten, open questions remain regarding the origin, nature, and position of satellite features that are prominent in the photoelectron spectrum. These satellites are a fingerprint of the electronic structure of the material and have not been thoroughly investigated, at times leading to their misinterpretation. The present work combines high-resolution soft and hard X-ray photoelectron spectroscopy (SXPS and HAXPES) with reflection electron energy loss spectroscopy (REELS) and a multi-tiered ab-initio theoretical approach, including density functional theory (DFT) and many-body perturbation theory (G0W0 and GW+C), to disentangle the complex set of experimentally observed satellite features attributed to the generation of plasmons and interband transitions. This combined experiment-theory strategy is able to uncover previously undocumented satellite features, improving our understanding of their direct relationship to tungsten's electronic structure. Furthermore, it lays the groundwork for future studies into tungsten based mixed-metal systems and holds promise for the re-assessment of the photoelectron spectra of other transition and post-transition metals, where similar questions regarding satellite features remain.

Band alignment of ultrawide bandgap ε-Ga2O3/h-BCN heterojunction epitaxially grown by metalorganic chemical vapor deposition

In this work, ultrawide bandgap ɛ-Ga2O3/h-BCN heterojunctions were epitaxially grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD). This heterojunction was systematically studied by various material characterization techniques, including X-ray diffraction (XRD), atomic force microscope (AFM), transmission electron microscopy (TEM), high-resolution X-ray photoelectron spectroscopy (HR-XPS), energy dispersive spectroscopy (EDS), and UV–Vis-NIR spectroscopy. h-BCN conformed to a two-dimensional layered structure, while ɛ-Ga2O3 grown on h-BCN was found to be polycrystalline. TEM and EDS element mapping showed a clear and sharp interface of the heterojunction. HR-XPS measurements were carried out to unveil the band alignment of the ε-Ga2O3/h-BCN heterojunction. It was found that the ε-Ga2O3/h-BCN heterojunction exhibits a type-II band alignment with a conduction band offset of 2.77 eV and a valence band offset of − 1.60 eV. This work provides valuable information on the epitaxial growth and band alignment of the ultrawide bandgap ɛ-Ga2O3/h-BCN heterojunctions, opening the door to a myriad of electronic and photonic applications.

Influence of POSS Type on the Space Environment Durability of Epoxy-POSS Nanocomposites.

In order to use polymers at low Earth orbit (LEO) environment, they must be protected against atomic oxygen (AO) erosion. A promising protection strategy is to incorporate polyhedral oligomeric silsesquioxane (POSS) molecules into the polymer backbone. In this study, the space durability of epoxy-POSS (EPOSS) nanocomposites was investigated. Two types of POSS molecules were incorporated separately—amine-based and epoxy-based. The outgassing properties of the EPOSS, in terms of total mass loss, collected volatile condensable material, and water vapor regain were measured as a function of POSS type and content. The AO durability was studied using a ground-based AO simulation system. Surface compositions of EPOSS were studied using high-resolution scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that with respect to the outgassing properties, only some of the EPOSS compositions were suitable for the ultrahigh vacuum space environment, and that the POSS type and content had a strong effect on their outgassing properties. Regardless of the POSS type being used, the AO durability improved significantly. This improvement is attributed to the formation of a self-passivated AO durable SiO2 layer, and demonstrates the potential use of EPOSS as a qualified nanocomposite for space applications.

Engineering the doping amount of rare earth element erbium in CdWO4: Influence on the electrochemical performance and the application to the electrochemical detection of bisphenol A

Rare earth elements Er doped CdWO4 (Er-CdWO4) nanorods were successfully prepared. The morphology, crystal structure, chemical environments and electrochemical properties of Er-CdWO4 nanomaterials were regulated by changing the doping amount of Er. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) have shown that the introduction of moderate content of Er could optimize the morphology of CdWO4. X-ray diffraction (XRD) results suggested that the larger Er ions partially replaced the Cd ions in CdWO4 nanocrystals and produced favorable lattice gaps and defects around the unit cell. The high-resolution X-ray photoelectron spectroscopy (XPS) of O 1 s and the enhanced peak intensity in electron spin resonance (EPR) declared that the doping of Er generated more oxygen vacancies in Er-CdWO4. Based on the physico-chemical characterizations, 0.5 wt% Er-CdWO4 was confirmed to be the best electrocatalyst within the tested samples, which exhibited the fastest electron transfer performance and the strongest electrocatalytic capacity to BPA. Taking the low-cost and simply prepared Er-CdWO4 with the optimal content of Er as the electrode modifier, a novel electrochemical sensor (Er-CdWO4/CPE) for BPA has been constructed for the first time, which exhibited the wide linear range from 0.01 to 6 μM and the limited detection of 0.003 μM, respectively. Moreover, satisfactory reproducibility, stability and anti-interference performance were also achieved on Er-CdWO4/CPE. Meanwhile, the proposed sensor successfully realized the determination of BPA spiked in local tap water samples.

Structure of Ge<sub><i>x</i></sub>Ga<sub>8</sub>S<sub>92–<i>x</i></sub> glasses studied by high-resolution X-ray photoelectron spectroscopy and Raman scattering

In this paper, the structures of chalcogenide glasses Ge<sub><i>x</i></sub>Ga<sub>8</sub>S<sub>92–<i>x</i></sub> (<i>x</i> = 24%, 26.67%, 29.6%, 32% and 36%) at a fixed Ga atomic content of 8% are studied by high-resolution X-ray photoelectron spectroscopy and Raman scattering spectra. In order to quantify the evolutions of the different structural units in Ge<sub><i>x</i></sub>Ga<sub>8</sub>S<sub>92–<i>x</i></sub> glasses, the number of double peaks in the Ge 3d, Ga 3d and S 2p spectra are determined by iterative fitting method, the binding energy and the full width at half maximum of each peak, and the relative ratio of the integral area of each decomposed peak to that of the whole area of the X-ray photoelectron spectroscopy are thus achieved. On the other hand, the Raman scattering spectra of Ge<sub><i>x</i></sub>Ga<sub>8</sub>S<sub>92–<i>x</i></sub> glass are decomposed into multiple Gaussians based on the structural units. We use the iterative method to simulate the position of peak center, full width at half maximum, and height of each Raman peak. By analyzing the evolution of each unit structure in the glasses, it is found that the network structure of glass network is mainly formed by S atom bridging the tetrahedral structure of GeS<sub>4</sub> and GaS<sub>4</sub>. The S chains or rings structural units are formed in Ge<sub>24</sub>Ga<sub>8</sub>S<sub>68</sub> glass, indicating that S atoms are in excess in the chemical composition of the glass, so there are enough S atoms around Ge and Ga atoms, forming heteropolar Ge—S and Ga—S bonds. With the gradual increase of Ge content, S chains or rings structure units rapidly disappear in Ge<sub>26.67</sub>Ga<sub>8</sub>S<sub>65.33</sub> glass. The Ge—Ge homopolar bonds in the ethane-like structure S<sub>3</sub>Ge—GeS<sub>3</sub> and the <i>M</i>—<i>M</i> (Ge—Ge, Ga—Ga or Ge—Ga) homopolar bonds in the S<sub>3</sub>Ge/Ga—Ga/GeS<sub>3</sub> structure simultaneous appear in the Ge<sub>29.6</sub>Ga<sub>8</sub>S<sub>62.4</sub> glass, and the number of structures increases gradually with the increase of Ge content. This is mainly due to the insufficient number of S atoms in the Ge-Ga-S glass. Once S atoms are lacking, the excess Ge and Ga atoms can only combine with themselves to form the homopolar bond <i>M</i>—<i>M</i>. It can be concluded below. Firstly, Ge and Ga atoms appear mainly in the form of 4-coordination, while S atoms occur mainly in the form of 2-coordination in the chalcogenide glasses of Ge<sub><i>x</i></sub>Ga<sub>8</sub>S<sub>92–<i>x</i></sub>. Secondly, the existence of <i>M</i>—<i>M</i> bond leads the nanophase to separate, and the ordering degree of glass network structure to decrease .

Characterization of front contact degradation in monocrystalline and multicrystalline silicon photovoltaic modules following damp heat exposure

Reliability and durability tests play a key role in the photovoltaic (PV) industry by minimizing potential failure risks for both existing and new cell and module technologies. In this work, a detailed study of contact degradation in monocrystalline and multicrystalline PV modules is performed. The modules are subjected to a sequence of damp heat (DH) exposures followed by electrical characterization after each step. Electroluminescence (EL) imaging shows different darkening patterns for monocrystalline modules compared to multicrystalline modules; the former shows darkening near the busbars and the latter shows it across virtually the entire cell surface. The primary loss mechanism is confirmed to be resistive after comparing the current-voltage ( I–V ) characteristics at each DH exposure step. Representative samples have been cored out from both the degraded modules and controls for materials characterization to gain further insights into the degradation mechanism. Top-down and cross-sectional scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and top-down high-resolution X-ray photoelectron spectroscopy (XPS) analysis performed on the cored samples confirm the degradation is due to metallization corrosion. Our study suggests that the difference in the darkening pattern can most likely be attributed to the different silver paste composition used for contacting each cell technology, particularly the composition of the glass frit. • Monocrystalline and multicrystalline PV modules show different cell darkening patterns in EL images after damp-heat exposure. • Performance losses are due to an increase in series resistance, not to any increase in the optical or recombination losses. • Primary reason for performance losses is the degradation of metal contacts, particularly the glass layer/metal-Si interface. • Sn migration from the interconnects to the metal contact surface plays a key role in accelerating the glass layer corrosion. • Difference in the darkening pattern can be attributed to the Ag paste composition used for contacting each cell technology.

Nickel-Decorated Mesoporous Iron–Cerium Mixed Oxides: Microstructure and Catalytic Activity in Methanol Decomposition

Nickel-decorated mesoporous cerium-iron oxide composites were synthesized by a combination of incipient wetness impregnation and template-assisted hydrothermal techniques. The effects of the Fe/Ce ratio and the calcination temperature of cerium-iron oxides on the phase composition, texture, structure, and redox properties of the composites were studied by a combination of N2 physisorption, XRD, high-resolution transmission electron microscopy, SEM, Mössbauer, Raman, XPS, ultraviolet-visible and FTIR spectroscopies, H2-temperature-programmed reduction, and total oxidation of ethyl acetate as a catalytic test. The combined physicochemical characterization and in situ FTIR investigation of methanol decomposition was used for a proper understanding of the microstructure of the Ni/FeCe oxide composites and the mechanism of the reaction occurring on them. The complex role of the FeCe support in the stabilization of highly dispersed Ni particles, the generation of surface intermediates, and the impact of the support phase transformation under the reaction medium are discussed.

Effect of Fe on Bi2Te3: Structure, magnetic properties, and XPS valence band

The crystal structure and magnetic properties of Fe doped Bi2Te3 are presented. The samples were studied by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and magnetization measurements. Rietveld refinement results show a decrease in volume due to the decrease in c lattice parameter as iron is introduced. By XPS measurements, the Te 3d, Bi 4f, Bi 5d, Te 4d, and Fe 3d core levels were identified, and the XPS valence band (VB) was measured. The deconvolution process of high resolution XPS spectra in Fe 3d orbital shows that the Fe3+ ion is present in the samples. Theoretical calculations by DFT reveal that the Bi2Te3 compound is a semiconductor with a narrow energy band gap in agreement with experimental results. DOS analysis shows that the main contributions to the valence band are the Te 5p, Bi 6p, and Fe 3d states. XPS VB shows a decrease in the intensity at zero eV due to increased Fe 3d states and good correspondence with DOS calculated for Bi2Te3. Finally, magnetic susceptibility measurements on Bi2Te3 do not show a magnetic behavior; however, for the doped sample with x = 0.2, a weak ferromagnetic behavior (WFM) below 14 K is observed.

Effect of Shewanella oneidensis MR-1 on U(VI) sequestration by montmorillonite

Bacteria may change the physicochemical properties of montmorillonite and further effect the disposal of high-level radioactive waste. Therefore, we explored the influence of Shewanella oneidensis MR-1 on the elimination of representative radionuclide U(VI) by montmorillonite (MMT). The batch experiments showed that MR-1 significantly enhanced the removal efficiency of U(VI), the adsorption capacity of MMT improved from 8.4 to 16.1 mg/g after addition of MR-1, and the adsorption type changed from Langmuir to Freundlich. FTIR and XPS analysis revealed that hydroxyl, phosphate, carbonyl and amine in MMT + MR-1 were primary actors in the elimination of U(VI). The U 4f high-resolution XPS spectrum of MMT + MR-1 showed U(VI) and U(IV) peaks at the same time, indicating that the adsorption process was accompanied by the reduction reaction, which may be due to the extracellular respiration of MR-1. These investigations are significant to insight the potential significance of microbial processes for the transport and elimination of U(VI) in repositories, which in return will contribute to their safe disposal.

Enhanced Photocurrent of the Ag Interfaced Topological Insulator Bi2Se3 under UV- and Visible-Light Radiations.

Bi2Se3 is a topological quantum material that is used in photodetectors, owing to its narrow bandgap, conductive surface, and insulating bulk. In this work, Ag@Bi2Se3 nanoplatelets were synthesized on Al2O3(100) substrates in a two-step process of thermal evaporation and magnetron sputtering. X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) revealed that all samples had the typical rhombohedral Bi2Se3. Field-emission scanning electron microscopy (FESEM)-energy dispersive x-ray spectroscopy (EDS), XPS, and HRTEM confirmed the presence of the precipitated Ag. The optical absorptance of Bi2Se3 nanoplatelets in UV-visible range decreased with the Ag contents. Results of photocurrent measurements under zero-bias conditions revealed that the deposited Ag affected photosensitivity. A total of 7.1 at.% Ag was associated with approximately 4.25 and 4.57 times higher photocurrents under UV and visible light, respectively, than 0 at.% Ag. The photocurrent in Bi2Se3 at 7.1 at.% Ag under visible light was 1.72-folds of that under UV light. This enhanced photocurrent is attributable to the narrow bandgap (~0.35 eV) of Bi2Se3 nanoplatelets, the Schottky field at the interface between Ag and Bi2Se3, the surface plasmon resonance that is caused by Ag, and the highly conductive surface that is formed from Ag and Bi2Se3. This work suggests that the appropriate Ag deposition enhances the photocurrent in, and increases the photosensitivity of, Bi2Se3 nanoplatelets under UV and visible light.

Enhanced high-temperature thermal conductivity of the reduced graphene oxide@SiO2 composites synthesised by liquid phase deposition

Liquid phase deposition was developed to synthesise thermally conductive reduced graphene oxide@SiO2 (rGO@SiO2) composites for use in aerobic environments above 600 °C. This method is a mild, controllable reaction, good repeatability, easy operation, and low cost. The composition, morphology, oxidation resistance property, thermal conductivity (TC) property, and deposition dynamics of the rGO@SiO2 composites were systematically investigated in this study. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and high-resolution X-ray photoelectron spectroscopy (XPS) measurements proved that SiO2 particles were synthesised on the rGO. Spherical SiO2 particles were uniformly dispersed on both sides of the rGO, the SiO2 particle size was relatively uniform (∼500 nm), and there was no excessive aggregation. Isothermal oxidation and TC analyses showed that the rGO@SiO2 composite possessed better high-temperature and oxidation-resistance properties compared to pristine rGO, while still exhibiting excellent TC in the out-of-plane direction (k⊥) at 650 °C after 24 h. Moreover, the deposition dynamics of the rGO@SiO2 composite were established based on the analysis results. The synthesis method, liquid phase deposition, provides a promising route for the mild and controllable synthesis of rGO-ceramic composites for thermal management materials.

Design a novel g-C3N4 based Ce2O3/CuO ternary photocatalysts for superior photo-degradation performance of organic mixed pollutants: Insights of Z-scheme charge transfer mechanism

In this work, a novel ternary g-C3N4/Ce2O3/CuO (GCC) composite photocatalyst was effectively synthesized by facile calcination and dynamic hydrothermal technique. The as-obtained photocatalysts (PCs) samples were characterized using several techniques such as XRD, FT-IR, FESEM-EDAX with mapping, HR-TEM, high-resolution XPS, UV-DRS absorption and PL spectra respectively. The photo-degradation outcomes specified that the ternary GCC composite PCs possessed the better photocatalytic efficiency by degrading for the aqueous MY (94.5%) and MB (90.3%) mixed dye compared to other as-obtained PCs samples within 150 min under visible-light exposure. Moreover, after the fifth recycles of the superior GCC composite PCs, the photo-degradation rate of MB and MY mixed dyes still could be reached to 81% and 86.5%, respectively, which revealed the excellent reusability and photostability after the five successive recycles. Hence, the improved photo-degradation activity could be ascribed to a lower bandgap, superior visible-light absorption capacity and reduced the recombination rate of photo-excited electron-hole (e−/h+) pairs among the synergistic effects of unique g-C3N4, Ce2O3 and CuO heterointerface in the efficient three-level e−/h+ transfer. Based on the various scavenger's tests, a probable charge transfer pathway with the strong reduction ability process was also proposed. The superior photo-degradation efficiency and their probability, which make reusable PCs and a potential aspirant for environmental wastewater purification and energy conversion.

Aminopropylimidazole as an Advantageous Coating in the Synthesis of Functionalized Magnetite Nanoparticles.

Implementing new methods to prepare magnetite nanoparticles with a covered or uncovered surface has been, and still is, a significant challenge. In this work, we describe a very clear and effortless way for the preparation of magnetite nanoparticles using two types of bases, namely: 1-(3-aminopropyl)imidazole and sodium hydroxide. Fourier transform infrared spectroscopy (FTIR) served as a tool for the structural investigation of the as-prepared magnetite nanoparticles. The morphology of the samples was investigated using Transmission Electron Microscopy (TEM). Comprehensive high-resolution X-ray photoelectron spectroscopy investigations (XPS) were applied as an effective tool for analyzing the composition of the various types of magnetic nanoparticles. Further polymer linkage was accomplished with poly(benzofuran-co-arylacetic acid) on the amino-functionalized surface of aminopropylimidazole-containing magnetic nanoparticles. The findings are promising for biomedicine, catalysis, and nanotechnology applications.

Trimetallic Ag@Pt-Rh core-shell nanocubes modified anode for voltammetric sensing of dopamine and sulfanilamide

Core-shell structured catalysts have attracted numerous attention due to their high utilization of metallic atoms, abundance of active sites, and high catalytic activity. Herein, Ag@Pt-Rh core–shell nanocubes were prepared by overgrowth of Pt-Rh on selective facets of Ag nanocubes via co-titration method for electrochemical detection of micropollutants such as dopamine (DA) and sulfanilamide (SA). The morphology and elemental distribution of Ag@Pt-Rh core–shell nanocubes were studied by TEM and high-resolution XPS. Results show that the Pt and Rh atoms were distributed uniformly on the surface of the Ag nanocubes. The electrochemical characterizations indicate that Ag@Pt-Rh NCs exhibited wide linear ranges of 0.2–512 µM with detection limits of 12 nM for determination of DA and a linear range of 2.6–320 μM with detection limits of 270 nM for monitoring SA. Thus, the Ag@Pt-Rh core–shell NCs may serve as a model for developing electrochemical sensors to monitor other biomolecules and pollutants.

Selective photocatalytic conversion of benzyl alcohol to benzaldehyde or deoxybenzoin over ion-exchanged CdS

The visible light absorbing CdS nanoparticles were partially modified with Au2S and Ag2S via a simple cation exchange process to prepare heterostructure photocatalysts (denoted as Au2S@CdS and Ag2S@CdS), which were employed for the conversion of aromatic alcohols to valued-added products, such as benzaldehyde and C-C coupling products, including deoxybenzoin and hydrobenzoin. When Au2S@CdS was used as the photocatalyst, benzaldehyde was obtained as the main product with a selectivity of 99%, and when Ag2S@CdS was used as the photocatalyst, deoxybenzoin was obtained as the main product with a selectivity of 95%. The critical photogenerated electron and hole transfer occurring during the photocatalytic reaction was systemically investigated by performing various control experiments and using in-situ high-resolution X-ray photoelectron spectroscopy. In addition, with the photocatalytic system proposed in this study, benzyl alcohol could be photoconverted into benzaldehyde or deoxybenzoin almost completely with high selectivity by altering the cocatalyst component via simple ion exchange.

Band alignment of type-I SnS2/Bi2Se3 and type-II SnS2/Bi2Te3 van der Waals heterostructures for highly enhanced photoelectric responses

Heterostructures based on new advanced materials offer a cornerstone for future optoelectronic devices with improved photoelectric performance. Band alignment is crucial for understanding the mechanism of charge carrier transportation and interface dynamics in heterostructures. Herein, we grew SnS2/Bi2X3 (X = Se, Te) van der Waals heterostructures by combining physical vapor deposition with chemical vapor deposition. The band alignment, measured by high-resolution X-ray photoelectron spectroscopy, suggested the successful design of type-I SnS2/Bi2Se3 and type-II SnS2/Bi2Te3 heterostructures. The SnS2/Bi2X3 heterostructure greatly improved the photoelectric response of a photoelectrochemical-type photodetector. The photocurrent densities in the type-I SnS2/Bi2Se3 and type-II SnS2/Bi2Te3 heterostructure-based devices were more than one order of magnitude higher than those of SnS2, Bi2Se3, and Bi2Te3. The improved photoelectric properties of the SnS2/Bi2X3 heterostructures can be explained as follows: (i) the photoexcited electrons and holes are effectively separated in the heterostructures; (ii) the charge-transfer efficiency and carrier density at the interface between the SnS2/Bi2X3 heterostructures and the electrolyte are greatly improved; (iii) the formed heterostructures expand the light absorption range. The photoelectric performance was further enhanced by efficient light trapping in the upright SnS2. The photoelectric response is higher in the type-I SnS2/Bi2Se3 heterostructure than in the type-II SnS2/Bi2Te3 heterostructure due to more efficient charge transportation at the type-I SnS2/Bi2Se3 heterostructure/electrolyte interface. These results suggest that suitable type-I and type-II heterostructures can be developed for high-performance photodetectors and other optoelectronic devices.

The synergistic effect of carbon edges and dopants towards efficient oxygen reduction reaction

Decoration with alien atoms and increasing the edge content are two valid ways to activate the oxygen reduction reaction (ORR) property of nanocarbons. To further enhance their intrinsic activity and explore the underlying ORR mechanism, graphene nanoribbons (GNRs) were selected as an ideal catalyst model. Theoretical simulations have predicted that with the synergistic effect between heteroatom-doping and edge sites, the ORR activity can be significantly improved. Inspired by this, N-GNRs were synthesized via the oxidative unzipping of CNTs followed by nitrogen incorporation with urea. Ample edges and nitrogen doping sites were detected by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. As a result, N-GNRs exhibited remarkably higher ORR properties in terms of onset and half-wave potentials, Tafel slopes, electron transfer number and methanol tolerance than either GNRs, the control sample without doping, or N-CNTs, the control sample without abundant edges, simply clarifying the significance of synergy between dopants and edges. Thus, this work provides a simple but efficient strategy to fabricate high-performance oxygen reduction catalysts.

Exploration of Copper Oxide Nanoneedle Electrosynthesis Applied in the Degradation of Methylene Blue.

In this study, we report a low cost, fast and unexplored electrochemical synthesis strategy of copper oxide nanoneedles films as well as their morphological and chemical characterization. The nanostructured films were prepared using electrochemical anodization in alkaline electrolyte solutions of ethylene glycol, water and fluoride ions. The film morphology shows nanoneedle-shaped structures, with lengths up to 1–2 μm; meanwhile, high-resolution X-ray photoelectron spectroscopy (HRXPS) and spectroscopy Raman analyses indicate that a mixture of Cu(II) and Cu(I) oxides, or only Cu(I) oxide, is obtained as the percentage of water in the electrolyte solution decreases. A preliminary study was also carried out for the photocatalytic degradation of the methylene blue (MB) dye under irradiation with simulated sunlight in the presence of the nanoneedles obtained, presenting a maximum degradation value of 88% of MB and, thus, demonstrating the potential characteristics of the material investigated in the degradation of organic dyes.

Impacts of surface nitridation on crystalline ferroelectric phase of Hf1-xZrxO2 and ferroelectric FET performance

This paper presents an approach to enhance Hf0.5Zr0.5O2 (HZO) ferroelectric orthorhombic phase (O-phase) formation via in situ NH3 plasma treatment. High-resolution non-disruptive hard x-ray photoelectron spectroscopy confirmed that O-phase formation can be enhanced by suppressed interfacial diffusion between HZO and the top TiN electrode. Additional N-bonding facilitated by NH3 treatment was shown to suppress the interaction between TiN and HZO, thereby reducing the formation of oxygen vacancies within HZO. It was shown to improve the reliability and ferroelectric performance (examined by the leakage current and positive-up-negative-down measurements) of HZO devices. After cyclic operations, NH3-treated ferroelectric FETs (FeFETs) exhibited stable transfer characteristics and memory windows, whereas untreated devices presented unstable behaviors. Our results demonstrate the efficacy of the proposed in situ NH3-treatment scheme in enhancing the stability of HZO-based FeFETs.