Al Kα X-ray Source Research Articles

Analysis of silver metal with a Thermo Scientific K-Alpha XPS instrument at 50 and 200 eV pass energies

Silver metal was analyzed by x-ray photoelectron spectroscopy using a Thermo Scientific K-Alpha instrument with an Al Kα x-ray source (1486.6 eV). The silver survey spectrum and high-resolution Ag 3d, Ag M4N45N45, Ag M5N45N45, Ag 3p, O 1s, C 1s, Ar 2p, Ag 4p, and Ag 4s narrow scans were obtained. The sample analyzed is the standard instrument calibration silver foil mounted inside the analysis chamber of the K-Alpha. Sputtering with monoatomic Ar+ was performed prior to analysis to remove surface contamination. Narrow and survey scans were collected at 50 and 200 eV pass energy, respectively.

Li7P2S8Br0.5I0.5 (LPSBI) solid state electrolyte by XPS

There have been increasing surface characterization studies of battery materials specifically in the context of before and after cell operation to determine any chemical changes. Therefore, providing reliable reference spectra of battery-related materials is important. In this paper, survey and high-energy resolution data are reported for the solid-state electrolyte Li7P2S8Br0.5I0.5, which has been synthesized and characterized at Pacific Northwest National Laboratory. The current data present narrow-scan regions of I 3d, I 4d, Br 3d, O 1s, P 2p, S 2p, and C 1s core-level spectra, as well as wide-scan survey data that were obtained using the Al Kα x-ray source with a Thermo Fisher Nexsa instrument.

Formation of cesium carbonate in ion-implanted graphite, examined with dual-source x-ray photoelectron spectroscopy, density functional theory calculations and thermodynamic modelling

A sample of highly orientated pyrolytic graphite (HOPG) was implanted with Cs+ ions in order to study the effect on the graphite matrix and the chemical form of Cs once embedded. The mean implantation depth was calculated to be ∼22 nm, allowing for investigation with X-ray Photoelectron Spectroscopy, (XPS), where both a traditional Al Kα X-ray source and a higher energy Ag Lα source was used for an increased sampling depth deeper into the surface. Analysis found that there was a reduction of sp2 C–C bonding with increasing implantation dose, resulting in a total loss of sp2 character at ∼6 atomic % Cs+. A striking increase in higher binding energy components (285.8–289.4 eV) in the C 1s spectra cannot be attributed solely to the presence of C–O species, instead indicating a dramatic re-ordering of the graphitic lattice to accommodate and neutralize the embedded Cs. XPS analysis indicates the formation of cesium carbonate within the graphitic material; this is reinforced by analysis of a Cs2CO3 reference sample. Additionally, thermodynamics equilibrium simulations, supported by simplified density functional theory (DFT) calculations, are performed, leading to strong agreement with the XPS findings; that is, the most stable form of Cs within the graphite matrix is expected to be cesium carbonate (Cs2CO3), which is in thermodynamic equilibrium with degraphitised HOPG and oxygenated degraphitised HOPG.

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids) for Efficient and Stable Perovskite Solar Cells

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids) for Efficient and Stable Perovskite Solar Cells

Dual Triplet Sensitization Strategy for Efficient and Stable Triplet–Triplet Annihilation Upconversion Perovskite Solar Cells

Dual Triplet Sensitization Strategy for Efficient and Stable Triplet–Triplet Annihilation Upconversion Perovskite Solar Cells

Influence of the carrier wafer during GaN etching in Cl2 plasma

In this study, we have performed a thorough characterization of the GaN surface after etching up to 100 nm in Cl2 plasma under various bias voltages and according to the carrier wafer used (Si, SiO2, Si3N4, and photoresist). The objective of this article is to evaluate the etch damage and contamination of the GaN surface when materials with other chemical nature are present during etching. The effects of etching conditions on surface morphology and chemical compositions of etched GaN films are studied in detail using XPS and AFM measurements. To this aim, a universal methodology is proposed to estimate accurately by XPS the stoichiometry of the GaN surface exposed to reactive plasmas when only an Al Kα x-ray source is available. The results indicate that the GaN etching mechanisms are very sensitive to the chlorine radical density present in the plasma, the latter being strongly influenced by the carrier wafer. Substrates that are more chemically reactive with Cl2 plasma such as silicon or photoresist compared to SiO2 or Si3N4 will lead to a greater loading of atomic chlorine, which in turn will lead to lower GaN etch rates. Moreover, the GaN surface contamination will depend on the etch by-products ejected by the carrier wafer. The GaN surface exposed to Cl2 plasma shows a Ga-depleted surface because of the more important reactivity of Cl with Ga rather than N, except in the SiO2 carrier wafer case. In this latter case, the formation of Ga–O bond limits the Ga removal. Regarding the surface roughness, it seems that the contaminants play a little role in the roughness formation except for the oxygen released by the SiO2 carrier wafer. On the other hand, the surface roughness evolution is clearly driven by the chlorine radical flux reaching the GaN surface. At low bias voltage, a preferential crystalline orientation etching driven by the Cl radicals leads to the formation of hexagonal shaped defects that are associated to screw-type threading dislocations already present in the pristine GaN material. At higher bias, the enlargement of the defects is limited, leading to a very low surface roughness value but to amorphized surfaces.

Li-ion solvation in TFSI and FSI -based ionic liquid electrolytes probed by X-ray photoelectron spectroscopy

For Li-ion batteries, the Li-ion solvation in liquid electrolytes is a crucial parameter affecting directly the electrochemical cycling performance. X-ray photoelectron spectroscopy (XPS) can play an essential role for investigating the cation and anion electronic structure and monitoring the Li-ion solvation into various solvent and salt environments. In this contribution, we demonstrate the capability of conventional laboratory XPS using Al Kα X-ray source to determine the anions solvation shell of Li+ cation within the low vapour pressure and vacuum compatible ionic liquid electrolytes. 1M of LiTFSI and 1M of LiFSI salts dissolved in (EMIM+-FSI-) and (EMIM+-TFSI-) ionic liquids respectively are investigated by acquiring the F1s, N1s, C1s, S2p and Li1s core levels. The binding energy difference between the N1s component originating from the EMIM+ cation and the N1s component originating from TFSI- or FSIanions solvating the Li+ confirms that both TFSI- and FSIcontribute simultaneously to the Li+ solvation. Additionally, the stability of the TFSI and FSI -based ionic liquid electrolytes is carefully discussed for long X-ray exposure times.

Efficient Electronic Modulation of g-C 3 N 4 Photocatalyst by Implanting Atomically Dispersed Ag 1 -N 3 for Extremely High Hydrogen Evolution Rates

Efficient Electronic Modulation of g-C ₃ N ₄ Photocatalyst by Implanting Atomically Dispersed Ag ₁ -N ₃ for Extremely High Hydrogen Evolution Rates

Versailles Project on Advanced Materials and Standards interlaboratory study on intensity calibration for x-ray photoelectron spectroscopy instruments using low-density polyethylene.

We report the results of a Versailles Project on Advanced Materials and Standards interlaboratory study on the intensity scale calibration of x-ray photoelectron spectrometers using low-density polyethylene (LDPE) as an alternative material to gold, silver, and copper. An improved set of LDPE reference spectra, corrected for different instrument geometries using a quartz-monochromated Al Kα x-ray source, was developed using data provided by participants in this study. Using these new reference spectra, a transmission function was calculated for each dataset that participants provided. When compared to a similar calibration procedure using the NPL reference spectra for gold, the LDPE intensity calibration method achieves an absolute offset of ∼3.0% and a systematic deviation of ±6.5% on average across all participants. For spectra recorded at high pass energies (≥90 eV), values of absolute offset and systematic deviation are ∼5.8% and ±5.7%, respectively, whereas for spectra collected at lower pass energies (<90 eV), values of absolute offset and systematic deviation are ∼4.9% and ±8.8%, respectively; low pass energy spectra perform worse than the global average, in terms of systematic deviations, due to diminished count rates and signal-to-noise ratio. Differences in absolute offset are attributed to the surface roughness of the LDPE induced by sample preparation. We further assess the usability of LDPE as a secondary reference material and comment on its performance in the presence of issues such as variable dark noise, x-ray warm up times, inaccuracy at low count rates, and underlying spectrometer problems. In response to participant feedback and the results of the study, we provide an updated LDPE intensity calibration protocol to address the issues highlighted in the interlaboratory study. We also comment on the lack of implementation of a consistent and traceable intensity calibration method across the community of x-ray photoelectron spectroscopy (XPS) users and, therefore, propose a route to achieving this with the assistance of instrument manufacturers, metrology laboratories, and experts leading to an international standard for XPS intensity scale calibration.

Ru(0001) and SiO2/Ru(0001): XPS study

X-ray photoelectron spectroscopy (XPS) is used to analyze the chemistry of the Ru(0001) film surface and the Ru/SiO2 interfacial region at different annealing conditions. The XPS spectra are collected under ultrahigh vacuum (base pressure of ∼5 × 10−10 Torr) condition using a SPECS electron spectrometer with a PHOIBOS 100 hemispherical energy analyzer and an XR 50 Al Kα x-ray source (1486.67 eV). High-resolution spectra of O 1s, Ru 3d/C 1s, and Si 2p together with survey scans are presented. The presence of 1 × 1 low energy diffraction pattern, collected from a 950 °C Ar/H2 step-annealed Ru(0001) sample, confirms the hexagonal periodicity of Ru(0001) surfaces.

On the X-ray photoelectron spectroscopy analysis of LiNixMnyCozO2 material and electrodes

X-ray photoelectron spectroscopy (XPS) is a widely used technique to study surface chemistry and ageing mechanisms of LiNixMnyCozO2 (NMC) based cathodes of lithium ion batteries. Analysis of the literature, however, reveals common problems in interpretation of their XPS spectra: (1) confusion of Ni2p spectra with Auger electron spectra (FKLL) of fluorine from commonly used PVdF binder and from decomposition of the fluorinated electrolyte components, when the XPS spectra are acquired with Al Kα X-ray source; (2) ambiguous fitting of the XPS spectral lines with several Lorentzian-Gaussian shapes leads to doubtful assignments of the oxidation states and questionable conclusions on the ageing mechanisms of the electrode materials. Revisiting the XPS data from aged NMC electrodes emphasizes the contribution of LiF and downplays the effect of nickel and manganese fluorides in the formation of cathode-electrolyte interface. To quantify Ni2+/Ni3+ ratio we introduce a novel method based on the ratio between Ni2p3/2 main peak intensity and intensity of the shake-up satellite. Applying this approach for commercial NMC333, NMC532, NMC622 and NMC811 powder materials we find good correlation with theoretically predicted values for freshly made materials.

Performance Test of a Laboratory-Based Ambient Pressure X-ray Photoelectron Spectroscopy System at the Gwangju Institute of Science and Technology

The performance test of a laboratory based ambient pressure X-ray photoelectron spectroscopy (AP-XPS) system at the Gwangju Institute of Science and Technology (GIST) was carried out. The system, consisted of a Scienta R4000 HiPP-3 electron analyzer and a monochromatized Al Kα X-ray source, is designed to operate a gas pressure of up to 25 Torr. An Al polyimide X-ray window is used to isolate the X-ray source from the back-filled-type ambient pressure measurement chamber. Two modes of XPS operations were tested, a one-dimensional chemical imaging mode and a transmission mode. In the transmission mode, the lens voltage of analyzer was optimized for maximum detection of photo-excited electrons under elevated pressure condition, i.e., a typical standard lens operation mode. On the other hand, in the imaging mode, spatial information on the outgoing electrons is conserved to generate a one-dimensional chemical image of surface being measured. The test of the imaging mode on a Au/Si reference sample showed a spatial resolution of ∼10 µm under an Ar gas pressure of 500 mTorr. With the superb design of the differential pump and the electron transfer optics, a good signal-to-noise ratio was obtained for the XPS core-level spectra at Ar gas pressure up to 1 Torr.

Investigation of Tm2O3 As a Gate Dielectric for Ge MOS Devices

Germanium (Ge) has been intensively investigated as a high-mobility channel material alternative to silicon (Si). A high quality Ge/dielectric interface with interface state density Dit compared to Si is required for competitive device performance. GeO2 has been identified as potential candidate for an interfacial layer (IL) due to effective Ge surface passivation with Dit in the range of 1011 cm-2eV-1 [1]. However, in order to achieve scaled effective oxide thickness (EOT) a combination of GeO2 IL and a high-k dielectric is needed. Low interface state density in the range of 1011 cm-2eV-1 has been achieved while employing Al2O3 barrier [2] as well as rare earth oxides such as Y2O3 [3]. Rare-earth thulium oxide (Tm2O3) provides high dielectric constant k~16 [4] and sufficient valence (3.05 eV) and conduction (2.05 eV) band offsets [5] for a high-k dielectric layer on Ge. In this work Ge/GeOx/Tm2O3 interface quality and the impact of post deposition anneal ambient are investigated. Metal oxide semiconductor (MOS) capacitors were fabricated to evaluate Ge/GeOx/Tm2O3 gate stacks. After n-Ge substrate clean (acetone, propanol and O2 plasma) and native germanium oxide removal with aqueous HF and HCl solutions the samples were immediately loaded into the rapid thermal anneal (RTA) chamber where oxidation was carried out at 550 °C for 5 s to 5 min. The temperature in the chamber is controlled by a pyrometer which is calibrated to a Si wafer, and oxidation is performed by placing a Ge substrate piece on a Si carrier wafer. The temperature of the Ge sample is thus lower than that of the Si wafer. After oxidation the samples were loaded to atomic layer deposition (ALD) chamber where 40 cycles (~7 nm) of Tm2O3 were deposited using TmCp3 and H2O as precursors. Then Ge/GeO2/Tm2O3 gate stacks were annealed in different ambient (O2, O3, N2 and H2/N2) and temperatures (400 - 550 °C). Reference samples without Tm2O3 deposition or without post deposition anneal (PDA) were also fabricated. Al gate metal was deposited by physical vapor deposition and patterned. MOS capacitors were electrically characterized with capacitance-voltage (CV) measurements. Interface state density in the midgap was evaluated from CV curves using a method described in [6]. X-ray photoelectron spectroscopy (XPS) was performed on some samples using Al Kα X-ray (1486.6 eV) source and PSP Vacuum Technology electron energy analyser. Electrical properties of thermally grown Ge/GeO2 interfaces were evaluated and low interface state density Dit < 5·1011 cm-2eV-1 in the midgap was extracted from CV measurements. The influence of Tm2O3 deposition on high-quality Ge/GeO2 interfaces was then determined. A degradation of the interface quality after the deposition was observed as displayed in Fig. 1. Dit is higher for thinner underlying GeOx layer and seems to saturate to ~9·1011 cm-2eV-1 for thick layers. A series of post deposition anneals in different ambient and temperatures were performed on Ge/GeOx/Tm2O3 gate stacks in order to investigate the influence on the interface state density and capacitance equivalent thickness (CET). The results are shown in Fig. 2. It can be seen that a temperature of 500 °C or higher and O2 ambient is needed to sufficiently reduce Dit, when values as low as 2·1011 cm-2eV-1 can be reached. XPS measurement was performed on Ge/GeOx/Tm2O3 gate stack with O2 PDA at 500 °C and the obtained spectrum is shown in Fig. 3. The difference between the GeOx 3d5/2 peak and Ge0 3d5/2 peak is 2.7 eV which corresponds to Ge3+ oxidation state. This result is consistent with previously reported XPS results on Ge/GeOx/Al2O3 stacks [7] and suggests that Ge3+ oxidation state provides the low Dit values of Ge/GeOx/Tm2O3 gate stacks. Tm2O3 integrated with GeO2 and O2 PDA is a viable candidate for Ge MOS devices due to low interface state density of ~2·1011 cm-2eV-1 which is correlated to Ge3+ oxidation state. A further investigation of O2 PDA time in terms of the trade-off between Dit and CET will be reported.

An in situ XPS study of L-cysteine co-adsorbed with water on polycrystalline copper and gold

The interactions of biomolecules with metal surfaces are important because an adsorbed layer of such molecules introduces complex reactive functionality to the substrate. However, studying these interactions is challenging: they usually take place in an aqueous environment, and the structure of the first few monolayers on the surface is of particular interest, as these layers determine most interfacial properties. Ideally, this requires surface sensitive analysis methods that are operated under ambient conditions, for example ambient pressure x-ray photoelectron spectroscopy (AP-XPS).This paper focuses on an AP-XPS study of the interaction of water vapour and l-Cysteine on polycrystalline copper and gold surfaces. Thin films of l-Cysteine were characterized with XPS in UHV and in a water vapour atmosphere (P ≤ 1 mbar): the structure of the adsorbed l-Cysteine layer depended on substrate material and deposition method, and exposure of the surface to water vapour led to the formation of hydrogen bonds between H2O molecules and the COO− and NH2 groups of adsorbed l-Cysteine zwitterions and neutral molecules, respectively. This study also proved that it is possible to investigate monolayers of biomolecules in a gas atmosphere with AP-XPS using a conventional laboratory Al-Kα x-ray source.

Water vapor electron scattering cross-section measurements using a hydrophobic ionic liquid

The interface of ionic liquid (IL) 1-ethyl-3-methylimidazolium-bis-(trifluoromethylsulfonyl)-imide, [EMIM][Tf2N], was examined in the presence of water vapor using lab-based ambient pressure X-ray photoelectron spectroscopy (APXPS) with a monochromatic Al Kα X-ray source. Room temperature water vapor exposures to [EMIM][Tf2N] ranged from 10−6 to 2.0Torr with no evidence of water uptake at the IL-vapor interface. The hydrophobic nature of [EMIM][Tf2N] allowed for measuring the attenuation of F 1s, O 1s, N 1s, C 1s and S 2p APXPS peaks as a function of pressure, allowing for the determination of the electron scattering cross-section (σe) of gas phase water. The elemental diversity of [EMIM][Tf2N] allowed for the extraction of σe over a 520eV kinetic energy range in the absence of a variable energy X-ray source. Herein we show that lab-based APXPS in combination with an elementally diverse, unreactive substrate is an effective tool for the determination of electron scattering cross sections for gas phase species.

Changing the surface properties on naval steel as result of non-thermal plasma treatment

The problem of corrosion, related to Biofouling formation, is an issue with very high importance in the maritime domain. According to new rules, the paints and all the technologies for the conditioning of naval materials must fulfil more restrictive environmental conditions. In order to solve this issue, different new clean technologies have been proposed. Among them, the use of non-thermal plasmas produced at atmospheric pressure plays a very important role. This study concerns the opportunity of plasma treatment for preparation or conditioning of naval steel OL36 type.The plasma reactors chosen for the experiments can operate at atmospheric pressure and are easy to use in industrial conditions. They are based on electrical discharges GlidArc and Spark, which already proved their efficiency for the surface activation or even for coatings of the surface. The non-thermal character of the plasma is ensured by a gas flow blown through the electrical discharges. One power supply has been used for reactors that provide a 5 kV voltage and a maximum current of 100 mA. The modifications of the surface properties and composition have been studied by XPS technique (X-ray Photoelectron Spectroscopy).There were taken into consideration 5 samples: 4 of them undergoing a Mini-torch plasma, a Gliding Spark, a GlidArc with dry air and a GlidArc with CO2, respectively the fifth sample which is the untreated witness. Before the plasma treatment, samples of naval steel were processed in order to obtain mechanical gloss. The time of treatment was chosen to 12 minutes. In the spectroscopic analysis, done on a ULVAC-PHI, Inc. PHI 5000 Versa Probe scanning XPS microprobe, a monocromated Al Kα X-ray source with a spot size of 100 μm2 was used to scan each sample while the photoelectrons were collected at a 45-degree take-off angle. Differences were found between atomic concentrations in each individual case, which proves that the active species produced by each type of plasma affects the surface properties of the treated naval steel.

All‐Solid‐State Cable‐Type Supercapacitors with Ultrahigh Rate Capability

All‐Solid‐State Cable‐Type Supercapacitors with Ultrahigh Rate Capability

Performance test of new near-ambient-pressure XPS at Korean Basic Science Institute and its application to CO oxidation study on Pt3Ti polycrystalline surface

A performance test of near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) at Korean Basic Science Institute (KBSI) in Daejeon, Korea is carried out. The NAP-XPS at KBSI is equipped with SPECS PHOIBOS 150 analyzer and 2-dimensional-delay line detector, which provides improved detection efficiency with 1-dimensional chemical imaging mode. The in-situ gas-pressure cell is designed to operate at pressure up to 25 mbar with differential pumping scheme. A micro-focused AlKα X-ray source is utilized as photon excitation source. The NAP-XPS is composed of two separate chambers, e.g. a main preparation chamber and a measurement chamber, which hold a low energy electron diffraction, a high pressure cell, an ion sputter gun, a multi-cell E-beam evaporators, and a four-axis manipulator with heating and cooling capability. As a test run of NAP-XPS, a CO oxidation experiment is carried out on Pt3Ti polycrystalline surface. During the active phase of CO oxidation, a clear formation of Ti oxide is found on surface, revealing the intriguing role of surface metal oxide in surface chemical reaction.

Sulfur-Doped Carbon with Enlarged Interlayer Distance as a High-Performance Anode Material for Sodium-Ion Batteries.

S-doped carbon is investigated as a high-performance anode material for sodium-ion batteries. Due to the introduction of a high-content of S atoms, the as-obtained S-doped carbon shows an enlarged interlayer distance. As an anode, a high specific capacity of up to 303 mAh g-1 is achieved, even after 700 cycles at 0.5 A g-1.

Increased photoelectron transmission in High-pressure photoelectron spectrometers using “swift acceleration”

A new operation mode of a HPXPS (high-pressure X-ray photoelectron spectroscopy) analyzer is evaluated on a HPXPS system fitted with an Al Kα X-ray source. A variety of metal foil samples (gold, silver and copper) were measured in different sample gas environments (N2 and H2O), and a front aperture diameter of 0.8mm. The new design concept is based upon “swiftly” accelerating the photoelectrons to kinetic energies of several keV after they pass the analyzer front aperture. Compared to the standard mode, in which the front section between the two first apertures is field-free, this gives a wider angular collection and a lower tendency for electron losses in collisions with gas molecules within the analyzer. With the swift-acceleration mode we attain, depending on the experimental conditions, up to about 3 times higher peak intensities in vacuum and about 10 to 20 times higher peak intensities in the 6–9mbar regime, depending on kinetic energy. These experimental findings agree well with simulated transmission functions for the analyzer. The new mode of operation enables faster data acquisition than the standard mode of operation, particularly valuable in a home laboratory environment. Further demonstrations of performance are highlighted by measurements of the valence band structure in dye-sensitized solar cell photoelectrodes under a 2mbar H2O atmosphere, a molecularly modified surface of interest in photoelectrochemical devices.