Band XPS Research Articles

Design of different oxygen content and high performance bilayer In2O3 thin-film transistors at room temperature for flexible electronics

In this study, homojunction bilayer In2O3thin film transistors (TFTs) were prepared by RF-magnetron sputtering at room temperature. Herein, an active channel of bilayer In2O3TFTs are consist of the front channel with lower (poor) oxygen content and the back channel with higher (rich) oxygen content. Therefore, optimizedbilayer In2O3TFT was fabricatedandaμFE of 32.5 cm2/Vs and a small SS of 280 mV/decade, a small VTH of 0.3 Vwere achieved. In addition, small VTH shifts of 0.7 (−1.0) and 0.4 (−1.2) V under gate bias and light illumination stress tests were obtained. Through XPS band structure analysis indicated that the formation of band bending between the channel layers leads to electron injection from the back channel into the front channel, resulting in accumulation of forming carriers near the interface of the bilayer, resulting in increase the μFE of In2O3TFTs. Furthermore, XPS and LFN measurement demonstrate that control the oxygen content can reduced the oxygen-related defects and bulk/interface trap density while controlling the Ne and carrier transport in the bilayer In2O3 film,which enhance the stability of In2O3TFTs. Overall, the high-performance bilayer In2O3TFTshave opena new method to obtaine the flexible electronic devices.

Zwitterionic surface modification of polyethylene via atmospheric plasma-induced polymerization of (vinylbenzyl-)sulfobetaine and evaluation of antifouling properties

Zwitterionic polymer brushes were grafted from bulk polyethylene (PE) by air plasma activation of the PE surface followed by radical polymerization of the zwitterionic styrene derivative (vinylbenzyl)sulfobetaine (VBSB). Successful formation of dense poly-(VBSB)-brush layers was confirmed by goniometry, IR spectroscopy, XPS and ToF-SIMS analysis. The resulting zwitterionic layers are about 50–100 nm thick and cause extremely low contact angles of 10° (water) on the material. Correspondingly we determined a high density of > 1.0 × 1016 solvent accessible zwitterions/cm2 (corresponding to 2,0 *10-8 mol/cm2) by a UV-based ion-exchange assay with crystal violet. The elemental composition as determined by XPS and characteristic absorption bands in the IR spectra confirmed the presence of zwitterionic sulfobetaine polymer brushes. The antifouling properties of the resulting materials were evaluated in a bacterial adhesion test against gram-positive bacteria (S. aureus). We observed significantly reduced cellular adhesion of the zwitterionic material compared to pristine PE. These microbiological tests were complemented by tests in natural seawater. During a test period of 21 days, confocal microscopy revealed excellent antifouling properties and confirmed the operating antifouling mechanism. The procedure reported herein allows the efficient surface modification of bulk PE with zwitterionic sulfobetaine polymer brushes via a scalable approach. The resulting modified PE retains important properties of the bulk material and has excellent and durable antifouling properties.

A metastable Cr4+-compound AlCrO3+δ, δ ≤ 0.5, grown at a nanocolloid, and its ultraviolet absorption, phonon bands, and dielectric properties

AlCrO3+δ, δ ≤ 0.5, is a Cr4+:CrO2 product of a metastable compound of two types Cr4+−3d2 electrons that determine its spin degree of freedom and allied magnetic/optical properties at a magnetic semiconductor. A nanocolloid of Cr6+ bonded via Al3+ and O2– in small micelles (a hydrogel) in water is explored to grow up AlCrO3+δ, δ ≤ 0.5, at hydrothermal reactions at microwave irradiation. It forms hexagonal plates (20–40 nm thickness) as annealed at 500 °C − 1000 °C (microwave). It has 4.69% larger X-ray crystal density of 4.848 g/cm3 than a usual phase, AlCrO3.5 → AlCrO3 + ¼O2↑, turned up on anneals at ≥ 1000 °C, at a larger bandgap, ≥ 4.2 eV, of a Cr3+−3d3 insulator. X-ray diffraction, XPS, electronic absorption, and phonon bands studied at duly annealed samples confer a Cr5+ → Cr4+ → Cr3+ charge ordering at anneals. A 700 °C annealed sample (others behave as an antiferromagnet, AFM) exhibits a ferromagnetic (FM) loop, with an unsaturated magnetization 9.2 emu/g (at 50 kOe fields), a coercivity 3.67 kOe, and a 0.1 MGOe energy-product at room temperature. The two types FM−AFM spins channels govern electrical conduction at major charge carriers Cr4+ → Cr3+ − e–, O2– vacancies, and ‘e–−h+’ electron-hole pairs as per applied frequencies. The results have renewed interest to design and develop spintronics-photonics at Cr4+−3d2 spin doped Al2O3 type oxides.

CuBi2O4/BiOBr composites promoted PMS activation for the degradation of tetracycline: S-scheme mechanism boosted Cu2+/Cu+ cycle

• The CBB-50/PMS/Vis system reached a TC removal of 90.3% within 35 min. • CBB-50 maintained high photocatalytic activity at a wide pH range from 2.5 to 10.5. • The Cu 2+ /Cu + cycle was remarkably boosted by the CBB-50 S-scheme heterojunction. The CuBi 2 O 4 /BiOBr S-scheme photocatalysts, combining 1D CuBi 2 O 4 nanorods and 2D BiOBr nanosheets were successfully synthesized by a hydrothermal method to activate peroxymonosulfate (PMS) towards efficient tetracycline (TC) degradation. Benefiting from the construction of S-scheme heterojunction, the Cu 2+ /Cu + cycle of CuBi 2 O 4 /BiOBr-50 (CBB-50) had been greatly boosted and further promoted the activation of PMS for TC degradation. Compared with bare CuBi 2 O 4 and BiOBr, CBB-50 could degrade 90.3% of TC within 35 min, and the degradation kinetic rate was notably increased by 8.4 and 3.3 times, respectively. The results of the cycling degradation experiment indicated that the as-prepared CBB-50 retained 91.7% of the degradation ability, implying its excellent stability. Interestingly, compared with the harsh pH requirements of traditional Fenton reactions, CBB-50 could perform photocatalytic reactions in the pH range of 2.5–10.5 and maintain excellent TC degradation performance. The scavenging experiments implied that SO 4 ·− /·OH/h + /·O 2 – / 1 O 2 were active species for the TC degradation. The XPS analysis, band structure and trapping results further verified that the transfer of photogenerated carriers conformed to the S-scheme mechanism. Considering its excellent performance, stability and applicability, CBB-50 would become a reliable candidate for the large-scale practical application of PMS activation in the degradation of antibiotics.

Effects of pyrolytic carbon on carburization strengthening and corrosion of 3YSZ hollow fiber membranes

Carbon species incorporation and carbon deposits are common in the manufacture process and application of yttria-stabilized zirconia (YSZ) ceramics, while the potential corrosion induced by the resultant carburization is unclear. The 3YSZ hollow fiber membranes were prepared by wet spinning method. A sintering procedure at 1300–1450 °C under 0.02 MPa oxygen partial pressure, and thereafter an oxidation treatment at 800 °C were applied to investigate the carbothermal reaction and carburization corrosion mechanism. It was found that the trace carbon species of 1.0–2.2 mol% derived from polymeric precursors triggered the carburizing strengthening of porous YSZ membranes without sacrificing porosity and deformability. However, the carburization corrosion also occurred at the mild oxidation treatment, resulting in deterioration in bending strength and integrated structure converting into fine grains. Raman spectra, XPS bands and HR-TEM images confirmed that the in-situ synthesized ZrCxOy oxidized into monoclinic ZrO2, and micro-cracking formed along grain boundaries, which led to substantial mechanical strength loss.

Ag nanoparticles-embellished Bi12GeO20 composites: A plasmonic system featured with reinforced visible-light photocatalytic performance and ultra-stability

In this study, various plasmonic binary composites Ag-Bi12GeO20 were fabricated through a facile in-situ photo-reduction route and subsequently analyzed by multitudinous techniques. The presence of both desirable ingredients in heterojunction structures were confirmed by XPS, SEM, TEM, and EDS elemental mapping and band structures were analyzed by UV–Vis DRS spectra. Moreover, steady-state and transient PL and electrochemical spectra were recorded to reveal effective spatial separation of charge carriers. The effective separation of charge carriers, reinforced visible-light absorption by local surface plasmon resonance effect of Ag nanoparticles, appropriate phase composition, and enlarged specific surface areas contributed to enhanced catalytic degradation of organic dye RhB and antibiotic TC and reduction of Cr (VI) under visible light. Specifically, the best candidate 1AB exhibited apparent reaction rate constants over degradation of RhB and TC and reduction of Cr (VI) about 5.0, 1.72, and 5.77 times those of bare Bi12GeO20 under the identical condition. In addition, basing on experimental and electrochemical analyses a possible photocatalysis mechanism was speculated for these robust and recyclable plasmonic binary composites. Such investigation would provide a novel alternative plasmonic system for environmental protection and mediation by means of photocatalytic technology.

Optical properties of heat-treated hierarchical structure of Eu3+ modified C-CaIn2O4 of small core–shell crystallites

A natural aloe-vera gel is promptly bridging the Eu3+, Ca2+ and In3+ species in a bio-complex of a polymer network, so as it yields a sample Eu3+:CaIn2O4 of small crystallites bonding over a grafted C-sp2 surface layer when it is burnt in a self-propagating combustion in air. The Eu3+ doped C-CaIn2O4 sample appears in a core–shell structure in part of the carbon forming a conjoint surface layer (shell) thereon of the individual crystallites in a hybrid nanostructure. The results are analyzed in terms of XRD patterns, phonon bands (in IR and Raman spectra), XPS bands, and hierarchical microstructure in the samples prepared with different Eu3+ dosages in finely tuning the microstructure and optical properties as useful for an efficient phosphor, optical display system, visible lasers, energy-converters, photocatalysts, optical imaging, medical tools, and several others. A partial Eu3+ → In3+ doping in a crystal lattice CaIn2O4 clearly reflects in a marked expansion of the lattice, as much as 2.2% found in the Eu3+ content progressively raised to 2.0 mol% in a tailored hybrid composite structure. An inbuilt C-sp2 shell structure of the crystallites is characterized in terms of its characteristic phonon bands in a conjoint polymer network, which are accounted well in modified XPS bands in the surface species.

Characteristics and performance of rutile/anatase/brookite TiO2 and TiO2–Ti2O3(H2O)2(C2O4)·H2O multiphase mixed crystal for the catalytic degradation of emerging contaminants

The as-synthesized rutile/anatase TiO2 and rutile/anatase/brookite TiO2–Ti2O3(H2O)2(C2O4)·H2O, particularly rutile/anatase TiO2, showed excellent catalytic oxidation of organic contaminants (MO and HBA).

Coexistence of ferromagnetic-type order and spin-glass-like behavior in Ce5AgGe2

In this study we report the magnetic properties of new ternary compound Ce5AgGe2. The electronic ground state properties of Ce5AgGe2 were characterized by magnetic susceptibility, magnetization, specific heat, and electrical resistivity measurements, and by investigations of the electronic structure (XPS study and band structure calculations). This novel phase was found to be ferromagnetic type with Curie temperature TC=14.6 K in coexistence with spin-glass-like phase. Ce5AgGe2 crystallizes in Mn5Si3P63/mcm structure with Ag and Ge atoms randomly distributed at 6g Wyckoff positions. To explain a variety of magnetic properties we analyzed different possibilities of the occupation of 6g sites by Ag atoms and the impact of the local atomic environment of Ce ions on its mixed (static) valence.

Translating XPS Measurement Procedure for Band Alignment into Reliable Ab Initio Calculation Method

Band alignment between solids is a crucial issue in condensed matter physics and electronic devices. Although the XPS method has been used as a routine method for determination of the band alignment, the theoretical calculations by copying the XPS band alignment procedure usually fail to match the measured results. In this work, a reliable ab-initio calculation method for band alignment is proposed on the basis of the XPS procedure and in consideration of surface polarity and lattice deformation. Application of our method to anatase and rutile TiO2 shows well agreement between calculation and experiment. Furthermore, our method can produce two types of band alignment: the coupled and the intrinsic, depending on whether the solid/solid interface effect is involved or not. The coupled and intrinsic band alignments correspond to alignments measured by XPS and electrochemical impedance analysis, respectively, explaining why band alignments reported by these two experiments are rather inconsistent.

ChemInform Abstract: Electronic Structure of the Heavy Fermion Superconductor Ce2PdIn8: Experiment and Calculations.

AbstractThe electronic structure of the heavy‐fermion superconductor Ce2PdIn8 is investigated by means of XPS and ab initio DFT band structure calculations.

Fly ash supported Ni―Fe solid acid catalyst for efficient production of diesel additive: intensification through far‐infrared radiation

AbstractNovel Ni―Fe solid acid catalyst was prepared through co‐wet impregnation of Fe2 (SO4)3·H2O and Ni (NO3)2·6H2O on fly ash (FA) support. XRD, BET‐BJH, SEM‐EDX, XPS and FTIR methods were employed to characterize the catalyst. The excellent catalyst activity was assessed and optimized in the production of methyl oleate (biodiesel/diesel‐additive). The response surface methodology (RSM) computed optimal parametric values pertaining to maximum oleic acid (OA) conversion (98.37 ± 0.01%) were 15:1 methanol/OA molar ratio, 1:15:2 nickel nitrate: ferric sulphate:FA (wt. ratio) and 4 wt.% (of OA) catalyst concentration in 1 h under conventional heating at mild reaction temperature (60 °C). The optimal catalyst possessed 27.64 m2/g specific surface area and 0.0233 cc/g pore volume with predominantly mesoporous framework. XPS bands confirmed the presence of Fe3+ and mixed Ni2+/Ni3+species rendering an acidity of 5.5 mmol KOH/g. The catalyst comprised of crystalline Fe2O3, Ni2O3 and NiS phases as revealed from XRD analysis. This study also reports the remarkable intensification of esterification reaction through an energy‐efficient application of far‐infrared radiation protocol (1/3rd of conventional power requirement) resulting 99.20% OA conversion in only 10 min at the derived optimal conditions. © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.

Electrochemical Detection of Four Prominent Tuberculosis Biomarkers Using Functionalized Titania Nanotubular Array Sensing Platform

Current available state-of-art tuberculosis (TB) detection techniques face four challenges: cost, time of detection, equipment portability, and performance. For rapid, point-of-care (POC) detection, sensing of volatile organic compounds (VOCs) from the breath is important for early diagnosis of several pulmonary diseases such as TB. VOCs such as methyl nicotinate, methyl p-anisate, methyl phenylacetate, and o-phenylanisole have been identified as prominent TB breath biomarkers. Sensing of VOCs using solid-state TiO2 nanotube array sensors is a robust method to detect VOC vapors. Highly ordered titania nanotubular arrays (TNA) were synthesized through electrochemical anodization and functionalized with cobalt. Passing nitrogen gas through an ethanol biomarker solution was used to deliver the vapor of the individual biomarkers to the sensor. Detection of biomarkers was carried out in amperometric mode at optimized bias potentials determined from cyclic voltammetry studies. The sensor response towards the biomarkers was calculated by subtracting the base current (only N2/ethanol) from the peak current obtained (N2/ethanol + biomarker). Varying the concentration of the biomarker in solution was used to determine the sensitivity of the sensors. Further, the sensitivity was also examined through electrochemical sensing of all the four biomarkers mixed in solution. The selectivity of the sensor was investigated by operating the sensor at different potentials when exposed to the mixture of biomarker vapors. The results illustrate that titania nanotubular morphology and cobalt are necessary for volatile organic biomarker (VOB) detection. Also, the sensor exhibits good sensitivity and selectivity towards the four prominent TB biomarkers. Further, mechanisms have been proposed to describe the attachment of the biomarkers to Co-TNA and are supported by XPS characterization and band theory.

Self-controlled growth of Fe 3BO 6 crystallites in shape of nanorods from iron-borate glass of small templates

Fe 3BO 6 can be an ideal compound for devising functional magnetic and dielectric properties in a single material for multiple applications such as electrodes, gas sensors, or medical tools. Useful to tailor such properties, here we report on a self-controlled Fe 3BO 6 growth in a specific shape of nanorods from a supercooled liquid precursor (an inorganic polymeric liquid or glass) of an initial composition (100 − x)B 2O 3 − xFe 2O 3, x = 40–50 mol%. B 2O 3 as a strong glass former co-bridges the Fe 3+ ions in oxygen polygons primarily in a 2-D interconnected polymer network so that it dictates preferably a 1-D directional growth on the reaction Fe 3+ species in form of a compound Fe 3BO 6, a favorable phase to nucleate and grow when annealing a precursor at 500–800 °C in ambient air. Distinct nanorods with a diameter ∼200 nm and 40–100 μm length have been formed on 10–15 min annealing a sample in microwave at moderate temperature 550 °C. A bonded surface B 2O 3 layer (15–25 nm thickness) has grown on the Fe 3BO 6 of the nanorods in situ in a specific structure. XPS bands in the Fe 3+, B 3+ and O 2− species confer this model structure. A local BO 3 → BO 4 conversion has incurred in the boroxol (B 3O 4.5) n , n → ∞, rings in the surface layer, showing three distinct IR bands at 1035, 1215 and 1425 cm −1.

Band diagram for chemical vapor deposition diamond surface conductive layer: Presence of downward band bending due to shallow acceptors

The properties of surface conductivity (SC) of impurity-non-doped CVD diamond (001) samples were studied by various methods of sheet-resistance ( R S ) measurement, Hall-effect measurement, XPS, UPS, SES, SR-PES, PEEM and 1D band simulation taking into account special emphases on deriving the information about the surface band diagram (SBD). The R S values in UHV conditions were determined after no-annealing or 200 ∼ 300 °C annealing in UHV. C 1 s XPS profiles were measured in detail in bulk-sensitive and surface-sensitive modes of photoelectron detection. The energy positions of valence band top ( E V) relative to the Fermi level ( E F) in UHV conditions after no-annealing or 200 ∼ 300 °C annealing in UHV were determined. One of the samples was subjected to SR-PES, PEEM measurements. The SBDs were simulated by a band simulator from the determined R S and E V − E F values for three samples based on the two models of surface conductivity, namely, so-called surface transfer doping (STD) model and downward band bending with shallow acceptor (DBB/SA) model. For the DBB/SA model, there appeared downward bends of SBDs toward the surface at a depth range of ∼ 1 nm. C 1 s XPS profiles were then simulated from the simulated SBDs. Comparison of simulated C 1 s XPS profiles to the experimental ones showed that DBB/SA model reproduces the C 1 s XPS profiles properly. PEEM observation of a sample can be explained by the SBD based on the DBB/SA model. Mechanism of SC of CVD diamonds is discussed on the basis of these findings. It is suggested that the STD model combined with SBD of DBB/SA model explains the surface conductivity change due to environmental changes in actual cases of CVD diamond SC with the presence of surface E F controlling defects.

Effect of Pt addition on vanadium-incorporated TiO2 catalysts for photodecomposition of ammonia

This study investigated the effect of adding Pt components to V-TiO2 for highly concentrated ammonia photodecomposition. Pt components were introduced to the V-TiO2 photocatalysts by using two method types: the common sol-gel (Pt-V-TiO2) and impregnation (Pt/V-TiO2) methods. The observed X-ray diffraction (XRD) peaks were assigned to V2O5 at 19.5, 27.5 and 30.20° in V-TiO2, and to Pt metals at 39.80° (111) in Pt/V-TiO2. The Pt component of Pt-V-TiO2 was identified at Pt2+ from the Pt4f7/2 and Pt4f5/2 bands at 73.6 and 77.4 eV in XPS bands, respectively, but the band was shifted to a lower binding energy in Pt/V-TiO2. The H2 temperature-programmed reduction (TPR) curves showed that the temperature of reduction from Ti3+ to Ti0 was decreased by Pt addition and that the area was larger in Pt-V-TiO2 than in Pt/V-TiO2. The NH3 decomposition was slightly increased with vanadium addition compared to that of pure TiO2, and the decomposition was further enhanced with Pt addition. Particularly, the NH3 (1,000 ppm) decomposition reached 100% over Pt/V-TiO2 after 120 min, although about 10–30% of the ammonia was converted into undesirable NO2 and NO.

Hydrogen production from methanol/water decomposition in a liquid photosystem using the anatase structure of Cu loaded [formula omitted

This study investigated the production of hydrogen over Cu (1, 5, 10 and 15 mol%)/ TiO 2 photocatalysts loaded with CuO, prepared by an impregnation method. The CuO (0 0 2 and 1 1 1 plane) peaks at 2 θ = 35 . 50 ∘ and 38.73° appeared with above 5 mol% loaded TiO 2 . The CuO component ( Cu 2 p 3 / 2 ) at 933.5–934 eV was shown in the XPS band of the Cu / TiO 2 photocatalysts, which increased in size with increasing amount of loaded Cu. All of Ti 2 p 3 / 2 bands for Cu / TiO 2 appeared at 458.8 eV, which were assigned to Ti 4 + , most likely due to pure TiO 2 . The measured full widths at half maximum (FWHM) of the Ti 2 p peaks for Cu / TiO 2 were larger compared to that of pure TiO 2 ; a larger FWHM implies a greater amount of less-oxidized metals. The ratios of metal-OH/metal-O in the O1s bands, which imply hydrophilicity, were increased in the Cu / TiO 2 compared to pure TiO 2 . The production of H 2 from methanol/water photodecomposition was greater over the Cu / TiO 2 photocatalysts than over the pure TiO 2 ; the production reached 13,500 μ mol after 10 h over 10 mol% Cu / TiO 2 .

Electronic Structure of Perovskite‐Type YBRh3: X‐Ray Photoelectron Spectroscopy and ab initio Band Calculations.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The investigation of carbon nitride films annealed at different temperatures

The effects of thermal annealing on the component and microstructure of carbon nitride films deposited by vacuum cathodic arc method are reported. The bonding structure of the films is investigated by Raman spectroscopy, FTIR, XPS and valence band XPS. Upon annealing, the N content of the film drops gradually from original 31.0 to 17.0 at.% at 600 °C. The results of Raman spectroscopy, FTIR and valence XPS demonstrate that the films below 500 °C mainly consist of aromatic cluster component and polymeric component, which is rather stable upon the increasing of anealing temperatures. With the further increasing of the annealing temperatures from 400 to 600 °C, the fraction of polymeric component decreases and the aromatic component develops greatly. Meanwhile the films tend to transform towards the fullerene-like microstructure, which can be seen from the large separation of the N 1s peaks (>2.0 eV). As a result the N sp 3 C bonds increase due to the rising of cross-linking between the graphite plane.

Electronic structure of perovskite-type YBRh 3: X-ray photoelectron spectroscopy and ab initio band calculations

The perovskite structure type YBRh 3 was synthesized by the arc melting method. Its electronic structure was studied by XPS and ab initio band calculations. The chemical shifts of the Y and Rh 3d levels from the elements were negative. The experimental and calculated valence band XPS coincided well with each other. The band calculation indicated that the metallic behavior of the compound originates from the Rh 4d electrons. The atomic distance between Y and Rh is 93% of the sum of the radii of the elements. The electron density has a maximum between the Y and Rh atoms, and the distance between the maximum point and center of the Y atom is 77% of its atomic radius. This indicates that charge transfer occurs from Y to Rh. The nearly equal electronegativities of B and Rh result in a covalent bond between them, which is shown as an asymmetric electron distribution in the circumference of the B and Rh atoms. The covalent bond results from hybridization of the B 2p and Rh 4d levels.