X-ray Photoelectron Spectroscopy Survey Research Articles

Physicochemical properties of in situ microwave-assisted germanium oxide modified nitrogen-doped carbon dots

Preparation of carbon dots (CDs) and nitrogen-doped carbon dots (NCDs) with germanium oxide (GeO2/GeO) using a facile one-step microwave-assisted synthesis procedure is presented. Iso-ascorbic acid, urea and Ge-132 were used as carbon, nitrogen and germanium sources, respectively. Studies have shown that the CDs, NCDs and GeO2/GeO nanoparticles individually have excellent qualities for bio-imaging applications including photoluminescence, biocompatibility, good stability and low toxicity. While CDs have been thoroughly explored in literature, CDs with germanium oxide on their surface are an avenue that has scarce information. Hence the synthesis and physicochemical characterizations of CDs- /NCDs- GeO2/GeO composites were studied using different microscopic and spectroscopic techniques to explore their compatibility for bio-imaging applications. In the presence of Ge, the approximate particle sizes of both the CDs and NCDs increased from 2.5 nm to 5.8 nm and the spherical or quasi-spherical shape was maintained. The X-ray photoelectron spectroscopy survey spectrum showed that the surface of Iso-N-Ge-CDs contained nitrogen and germanium, indicating the successful synthesis of nitrogen-doped carbon dots (NCDs) with germanium oxide (GeO2/GeO). Photoluminescence emissions of longer wavelengths suitable for cell imaging were observed for Iso-N-Ge-CDs (350 nm) and Iso-Ge-CDs (430 nm) and the Iso-N-Ge-CDs are able to fluoresce under the red and blue wavelengths. The Ge-NCDs demonstrated excitation-dependent emission wavelength behaviour, pH sensitivity and Fe3+ sensitivity which may be used as a probe for Fe3+ metal ions and intracellular pH measurements.

The Photochemical Stability of PbI2 and PbBr2: Optical and XPS and DFT Studies

We investigated the photochemical stability of PbX2 (X = I and Br) halides by optical and X-ray photoelectron spectroscopy (XPS). The optical absorbance displayed a strong reduction for PbI2 with light soaking and permanent behavior for PbBr2. The XPS survey spectra showed a sharp drop in the I:Pb ratio for PbI2 from 1.63 to 1.14 with exposure time from 0 to 1000 h while for PbBr2, it remains practically unchanged (1.59–1.55). The measurements of the XPS Pb 4f and Pb 5d spectra have shown the partial photolysis of PbI2 with the release of metallic lead whereas PbBr2 demonstrated remarkable photochemical stability. According to the density functional theory (DFT), calculations of the metal and iodide vacancy formation energies for PbBr2 are higher than for PbI2 which confirms the better stability to light soaking. The high photochemical stability of PbBr2 means that it can be used as excess under MAPbBr3 perovskite synthesis to improve not only the power conversion efficiency but also stability to light soaking.

The Role of Diethanolamine on Chemical Mechanical Polishing in Alkaline Glycine-Based Slurries for Cobalt Interconnects

Cobalt (Co) and its low resistivity, superior adhesion property, and void-free seamless fill ability, pledge to transform the landscape of integrated circuits in many areas, especially in interconnects and logic contacts. Chemical mechanical polishing (CMP), which can realize local and global planarization, has been recognized as one of the indispensable manufacturing approaches for the fabrication of multilevel metal interconnection structures. The present work introduces diethanolamine (DEA) into our alkaline glycine-based slurries for Co CMP process. The action mechanism of DEA on Co CMP process in glycine-based slurries at pH 8.1 has been clearly revealed by various approaches, including polishing and static etching experiments, X-ray photoelectron spectroscopy survey, electrochemical analysis, as well as adsorption isotherm calculation. At low concentrations, DEA could be able to accelerate the polishing process via its auxiliary complexing effect, obtaining higher removal rates and larger corrosion current densities. Some pitting corrosion could appear on Co surfaces due to the production of Co-glycine complex as well as the auxiliary complexing process, making rougher surface qualities. On the other hand, when the DEA concentration increased to a certain level, it could play a role of corrosion inhibitor, protecting Co surfaces by forming a stable passive layer and moderating material removal rates, removal selectivity, and surface roughness.

The role of dipotassium ethylenediaminetetraacetic acid and potassium oleate on chemical mechanical planarization relevant to heterogeneous materials of cobalt interconnects

Cobalt (Co) with its low resistivity, superior adhesion property, and void-free seamless fill ability, pledges to transform the landscape of integrated circuits in many areas, especially in interconnects and logic contacts. The present work describes the selection and optimization process of the complexing agent and inhibitor in chemical mechanical polishing barrier slurries relevant for heterogeneous materials of Co interconnects. An alkaline colloidal silica based slurry has been proposed, consisting of 0.5 wt% hydrogen peroxide, 5 mM dipotassium ethylenediaminetetraacetic acid (EDTA-2K), 13 mM potassium oleate (PO) and producing a Co removal rate of 45.6 Å/min, along with an appropriate removal rate selectivity between oxide dielectric, barrier layer and Co, which reaches above ∼ 2:1:1. Furthermore, synergetic effects of the oxidizer, complexing agent EDTA-2K and inhibitor PO on the Co CMP process have been investigated systematically by several analytical techniques, including electrochemical analysis, X-ray photoelectron spectroscopy survey, and adsorption isotherm characterization. The role of EDTA-2K affecting SERs and MRRs embodies in its strong complexing ability by dissociating to full deprotonated EDTA ion and then reacting with Co to produce very stable chelate Co(Ⅱ)EDTA. Moreover, the effect of inhibitor PO has a critical point. With the addition of PO at a low concentration, an effective passivation layer could be formed on Co surfaces spontaneously via chemisorption, protecting Co from severe pitting corrosion. While in case of PO at high concentration, Co(Ⅱ)PO ligand will be generated, reducing the stability of the original PO-Co passive layer and providing paths for complexing agent EDTA-2K to produce Co(Ⅱ)EDTA chelate.

2H-MoS 2 Modified Nitrogen-Doped Hollow Mesoporous Carbon Spheres as the Efficient Catalytic Cathode Catalyst for Aprotic Lithium-Oxygen Batteries

2H-MoS ₂ Modified Nitrogen-Doped Hollow Mesoporous Carbon Spheres as the Efficient Catalytic Cathode Catalyst for Aprotic Lithium-Oxygen Batteries

Defect Passivation via Isoxazole Doping in Perovskite Solar Cells.

To improve perovskite solar cell (PSC) performance, which is deeply related to perovskite layer quality, researchers have explored numerous strategies. Additive doping into perovskite precursors has been widely used to improve the PSC performance. In this study, we used isoxazole—a Lewis-base small molecule—as an additive for the CH3NH3PbI3 (MAPbI3) precursor and explored how isoxazole effectively passivates defects in the perovskite structure. We found that isoxazole interacted with undercoordinated Pb2+ ions from an X-ray photoelectron spectroscopy survey and verified that isoxazole doping improved the device performance. When the optimized concentration of isoxazole was doped in the MAPbI3 precursor, the power conversion efficiency increased from 15.6 to 17.5%, with an improved fill factor and short-circuit current density. In addition, an isoxazole-doped device sustained 94% of its initial performance after 8 days under ambient air conditions (10 ± 5 RH %, 25 °C), whereas a device without isoxazole doping only maintained 64% of its initial performance.

Spectroscopic Insights into the Near-Infrared Polaronic Transitions in Surface-Passivated Substoichiometric MoO3–x Nanodots

Oxygen vacancies are the key factor that significantly influences physical and/or chemical properties of substoichiometric transitional metal oxide nanomaterials. In this study, we evaluate substoichiometric MoO3–x nanodots protected by penicillamine. In the synthesis, a carboxylic thiol reduction protocol is followed by a hydrothermal treatment, which makes the purification and isolation procedures facile. The obtained MoO3–x nanodots are well redispersed in both water and N,N-dimethylformamide, allowing us to examine the influence of the dispersion solvent on their optical properties. The nanodots exhibit three absorption peaks in the near-infrared (NIR) region, and their positions do not depend on the dispersion solvent, suggesting that the NIR absorption is originated not from the plasmonic resonances but from polaronic transitions caused by the oxygen vacancies. However, the spectral linewidth and intensity for the two lower-energy peaks strongly depend on the solvent, whereas those for the highest-energy peak do not. Magnetic circular dichroism measurements additionally reveal that the highest-energy peak arises from two interacting polaronic transitions that are close in energy, giving a derivative-like response based on the Faraday B term. Since the X-ray photoelectron spectroscopy survey shows that the main defect centers are different between the surface and inside of the nanodots, we propose a new mechanism to account for the NIR transitions from a viewpoint of bulk and surface polarons.

Qualitative surface characterization of Indian Permian coal using XPS and FTIR

ABSTRACT This paper reports on the surface properties associated with high-ash Indian Permian coal, which primarily depend on its geochemical compositions. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) techniques have been used to assess surface properties. The results confirm the presence of different elements, mineral phases, and organic functional groups in coal. The XPS survey confirms the presence of different elements on the surface of the coal. Some of them are C 1s (286.0 eV), O 1s (534.5 eV), N 1s (399.9 eV), S 2p (158.2 eV), such as SiO2 and Al2O3, which correspond to Si 2p (102.7 eV) and Al 2p (75.6 eV) with other clay minerals. XPS spectra of C 1s confirm the presence of aliphatic and aromatic carbon, which are hydrophobic compared to hydrophilic groups such as alcoholic, carboxylic, and phenolic. FTIR also validates the existence of hydrophobic functional groups as being higher than hydrophilic groups. Proximate and ultimate analysis results also confirm the presence of less moisture and a higher carbon percentage in the coal samples. Hence, the inherent hydrophobicity of the coal surface is excellent, and the surface hydrophobicity of coal can also be characterized using XPS and FTIR techniques. This information about the coal properties will be very beneficial for coal beneficiation and utilization.

Constructing ultra-stable photothermal plastics assisted by carbon dots with photocaged reactivity

Constructing ultra-stable photothermal plastics assisted by carbon dots with photocaged reactivity

Controlled Growth Interface of Charge Transfer Salts of Nickel-7,7,8,8-Tetracyanoquinodimethane on Surface of Graphdiyne

Controlled Growth Interface of Charge Transfer Salts of Nickel-7,7,8,8-Tetracyanoquinodimethane on Surface of Graphdiyne

Study of the Layer-Type BST Thin Film with X-ray Diffraction and X-ray Photoelectron Spectroscopy

In the present paper, results of X-ray photoelectron studies of electroceramic thin films of barium strontium titanate, Ba1−xSrxTiO3 (BST), composition deposited on stainless-steel substrates are presented. The thin films were prepared by the sol-gel method. A spin-coating deposition of BST layers with different chemical compositions was utilized so the layer-type structure of (0-2) connectivity was formed. After the deposition, the thin-film samples were heated in air atmosphere at temperature T = 700 °C for 1 h. The surfaces of BST thin films subjected to thermal treatment were studied by X-ray diffraction. X-ray diffraction measurements confirmed the perovskite-type phase for all grown thin-film samples. The oxidation states of the elements were examined by the X-ray photoelectron spectroscopy method. X-ray photoelectron spectroscopy survey spectra as well as high-resolution spectra (photo-peaks) of the main metallic elements, such as Ti, Ba, and Sr, were compared for the layer-type structures, differing in the deposition sequence of the barium strontium titanate layers constituting the BST thin film.

Bidirectional Light-Driven Ion Transport through Porphyrin Metal–Organic Framework-Based van der Waals Heterostructures via pH-Induced Band Alignment Inversion

Bidirectional Light-Driven Ion Transport through Porphyrin Metal–Organic Framework-Based van der Waals Heterostructures via pH-Induced Band Alignment Inversion

Retraction Note to: Structural and electrochemical impedance spectroscopic studies on reactive magnetron sputtered titanium oxynitride (TiON) thin films

Titanium oxynitride films were deposited onto commercially pure titanium substrates by direct current reactive magnetron sputtering method using Ti targets and an Ar–N2–O2 mixture discharge gas. The X-ray photoelectron spectroscopy survey spectra on the etched surfaces of TiON films exhibited the characteristic Ti 2p, N 1s, and O 1s peaks at the corresponding binding energies 454.5, 397.0, and 530.7 eV, respectively. The surface topography of these coatings was studied using atomic force microscopy. The characteristic Raman peaks at 200 and 641 cm−1 for the TiN bonds and at 148, 398 ,and 518 cm−1 for the TiO2 bonds were observed from the Laser Raman spectrometer. The potentiodynamic polarization studies in simulated bodily fluid were performed and the results are reported in this article.

XPS study of iodine and tin doped Sb2S3 nanostructures affected by non-uniform charging

X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements are used for investigating incorporation of iodine and tin into the stibnite (Sb2S3) lattice, as well as for determining surface composition and structure, respectively. The XRD analysis revealed the visible presence of a single phase, that of pure orthorhombic Sb2S3 structure. XPS survey spectra confirmed the presence of expected elements (Sb, S, Sn and I) at the surface of corresponding samples. Since the bonding identification was hindered by non-uniform charging of samples during acquiring the photoelectron spectra, a novel approach for the analysis of high resolution spectra was proposed and successfully implemented. XPS results showed that surface composition of the non-doped sample coincides with that of the bulk, while doping strongly affects surface of the samples. Sn-doped sample appears to be prone to surface oxidation. The presence of Sb2S3, Sb2O3, SnS2 and Sn(0) phases at the surface was revealed. Strong segregation of antimony was observed in the I-doped Sb2S3 sample. Iodine is also present at the surface in the form of the SbI3 phase, while the detected sulphur signal most probably corresponds to S atoms from unaltered deeper layers.

Rare-Earth Doping Graphitic Carbon Nitride Endows Distinctive Multiple Emissions with Large Stokes Shifts

Rare-Earth Doping Graphitic Carbon Nitride Endows Distinctive Multiple Emissions with Large Stokes Shifts

Optimization of substrate-selective atomic layer deposition of zirconia on electroplated copper using ethanol as both precursor reactant and surface pre-deposition treatment

Recent developments on the further optimization of the selective atomic layer deposition (ALD) of zirconium oxide (ZrO2) onto silicon over electroplated copper are reported with tris(dimethylamino)cyclopentadienyl zirconium as the zirconium precursor and ethanol as both oxygen source for precursor and pretreatment of copper surface to reduce surface oxides. A comparison between the electroplated (EP) and e-beam deposited (EB) copper before ALD using high-resolution X-ray photoelectron spectroscopy (XPS) showed EP Cu having more oxides on the surface and unexpectedly the EP Cu was found to have higher selectivity of ALD. In addition, a comparison of deposition of zirconia on silicon over EP and EB copper substrates for 70 ALD cycles show experimental conditions can impact the degree of selective deposition with the electroplated copper. With further optimization of the substrate pretreatment and ALD process parameters, both XPS survey analysis and ellipsometry showed ALD selectivity was enhanced up to 100 cycles on electroplated copper samples which is higher than ever previously reported forming an amorphous ZrO2 film of ~ 3 nm thickness on silicon and no deposition on copper. Lack of crystallinity of the ALD ZrO2 films is manifested by X-ray absorption fine structure and grazing incidence X-ray diffraction. Atomic force microscopy and scanning electron microscopy performed on the samples indicated no significant changes of the roughness and topography on the samples before and after ZrO2 ALD. Both thermodynamic calculations and experimental data presented here show that ALD selectivity is mainly dictated by the balance of the total amounts of oxygen and carbon in the reactor along with the ALD conditions and reactor design. These studies show pre-deposition ethanol exposure of the substrate, deposition/adsorption of reduction byproducts formed, and the total oxygen and carbon in the ALD reactor are important contributors to whether ALD selectivity can be significantly enhanced or even achieved at all.

Practical guide to the use of backgrounds in quantitative XPS

This guide is intended for both the novice in x-ray photoelectron spectroscopy (XPS) as well as users with some experience. XPS is one of the most widely used methods to characterize surface nanostructured samples, and XPS is now also commonly accessible to most material scientists through XPS facility centers. It is, therefore, increasingly used as a routine analysis technique to complement other techniques. This has led to an increase in the number of users who may not have a full understanding of the details of XPS and consequently must rely on the report provided by the XPS center. The purpose of this practical guide on the aspects of quantitative XPS is first to put the reader in a position to be able to understand and judge the meaning and possible errors in atomic concentrations based on analysis of peak intensities, which is the standard way quantitative XPS is reported. We discuss different ways to improve the analysis. This is attained by giving the reader a good understanding of how the intensities in the peak and the background of inelastically scattered electrons are linked together through the depth distribution of atoms. We then explore how this can be applied to greatly increase the capabilities of XPS to more accurately determine the composition and structure of surfaces on the nanoscale. This is possible at different levels of sophistication. We first see how a visual inspection of the XPS survey spectrum can be applied to get a quick rough indication of the structure. Next, we go through other more quantitative methods that are being used. The practical application of these techniques is illustrated by several examples.

Controlled Synthesis of Porous Carbon Nanostructures with Tunable Closed Mesopores via a Silica-Assisted Coassembly Strategy

Controllable fabrication of mesoporous carbon nanoparticles (MCNs) with tunable pore structures is of great interest, due to the remarkable effect of pore structure on electrochemical performance o...

Oxidized Black Phosphorus Nanosheets as an Inorganic Antiresorptive Agent

Black phosphorus (BP) is a newly discovered two-dimensional material that has promising applications from bioelectronics to biomedicine. However, facile oxidation of BP leads to changes in surface ...

Tunable luminescence of Eu3+ -activated CaWO4 nanophosphors via Bi3+ incorporation.

A series of CaWO4 :3Eu3+ :xBi3+ (x = 2, 5, 7 and 10 at.%) nanophosphors was prepared through the efficient low-temperature ethylene glycol route. Their structural, as well as photophysical, properties were studied. X-ray diffraction analysis and a X-ray photoelectron spectroscopy survey confirmed that the Bi3+ and Eu3+ ions incorporated perfectly into Ca2+ and without disturbing the lattice. The samples exhibited almost spherical morphology with average particle sizes from 10 to 30 nm. For the nanoparticles, Fourier transform infrared spectroscopy featured broad absorption bands around 871 and 778 cm-1 that were due to antisymmetric stretching, whereas a peak at 435 cm-1 was assigned to antisymmetric bending vibrations of the bonds in [WO4 2- ] clusters. The nanophosphors showed orange-red luminescence, which was further tuned to red by incorporation of sensitizer Bi3+ ions. This colour tuning of the nanoparticles is described in the context of energy transfer from the WO4 2- group to sensitizer Bi3+ and activator Eu3+ ions under 394 nm excitation. A CIE diagram supports this colour tunability.