Monochromated Al Kα X-rays Research Articles

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

Experimental determination of electron attenuation lengths in complex materials by means of epitaxial film growth: Advantages and challenges

Accurate electron attenuation lengths are of critical importance in using electron spectroscopic methods to quantitatively characterize complex materials. Here, the authors show that analysis of core-level and valence-band x-ray photoelectron spectra excited with monochromatic AlKα x-rays from the substrate and measured as a function of film thickness can be used to determine electron attenuation lengths in epitaxial SrTiO3 films on Ge(001). Closely lattice-matched epitaxial heterojunctions are ideal systems for determining attenuation lengths provided the films grow in a layer-by-layer fashion, leading to atomically flat surfaces, and the buried interfaces are atomically abrupt. In principle, either the rate of attenuation of substrate peak intensities or the rate of increase of film peak intensities can be used for this purpose. However, the authors find that structural nonuniformities in the films reduce the accuracy of electron attenuation lengths determined from photoelectrons that originate within the films. A more reliable source of information is found in photoelectrons from the substrate which traverse the film. By using the energy dependence of calculated electron attenuation lengths from the NIST database in combination with Ge 3d core and Ge-derived valence-band intensities, the authors determine electron attenuation length as a function of kinetic energy for SrTiO3.

Core-level spectra of powdered tungsten disulfide, WS2

Core level spectra, generated by monochromatic Al Kα x-rays for a commercial, powdered tungsten disulfide (WS2) specimen, have been recorded and presented. The x-ray photoelectron spectra of WS2 obtained include a survey scan, high-resolution spectra of W 4f, S 2p, S 2s, W 4d, W 4p, O 1s, W 4s, S LMM, and the valence band. Quantitative analysis has been achieved using a two-parameter Tougaard background and line shapes indicated for fitting; using these methods a surface composition of WS2 is found.

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.

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

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

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.

As-Received,Ozone Cleaned and Ar+ Sputtered Surfaces of Hafnium Oxide Grown by Atomic Layer Deposition and Studied by XPS

XPS survey and multiplex spectra were collected from 47 nm thick HfO2 films grown by atomic layer deposition (ALD). Measurements were made for as-received, ozone cleaned and surfaces cleaned by sputtering with 2kV Ar+ for 180 sec. The data were collected on a Physical Electronics Quantum 2000 Scanning ESCA Micoprobe using monochromatic Al Kα x-ray (1486.7 eV) excitation. The ALD films were grown using tetraethylmethylaminohafnium (TEMAH) as a precursor. Survey spectra showed the presence of C, O and Hf. Surface hydrocarbon contamination made up approximately 19 atom percent (at%) or approximately 0.5 monolayers (ML) of the as received surface concentration. After treatment by UV in air, the surface hydrocarbon concentration was reduced to approximately 2.5 at% or 0.06 ML. The 1 at% of carbon that remained after sputtering had a binding energy characteristic of carbide believed to be formed by the ion sputtering process. The formation of the low binding energy Hf 4f lines indicates reduction of the Hf oxide due to preferential sputtering.

Beam damage of HS(CH2)15 COOH Terminated Self Assembled Monolayer (SAM) as Observed by X-ray Photoelectron Spectroscopy

XPS spectra of a HS(CH2)15 COOH terminated self assembled monolayer (SAM) sample were collected over a period of 231 min to determine specimen damage during long exposures to monochromatic Al Kα x-rays. For this COOH terminated SAM the loss of oxygen was measured as a function of time while rastering a focused 100 W, 100 μm diameter x-ray beam over a 1.4 mm × 0.2 mm area of the sample.

An independent confirmation of the correlation of Uf4 primary peaks and satellite structures of UVI, UV and UIV in mixed valence uranium oxides by two-dimensional correlation spectroscopy

Two-dimensional (2D) correlation spectroscopy was used to resolve the positions and correlations among U4f primary peaks and satellite structures of UIV, UV and UVI components on a dry mica surface. These different species resulted from the reduction of UVI, initially sorbed/precipitated from solution, upon exposure to a high flux of monochromatic Al Kα X-rays during X-ray photoelectron spectroscopy. Synchronous and asynchronous 2D maps of these results are consistent with previous assignments to UIV, UV and UVI components of the solid. The synchronous spectra confirmed the negative correlation between UVI and UIV components and the asynchronous spectra confirmed the role of UV as a reactive intermediate in the reduction reaction of UVI to UIV. Simulations of 2D correlation maps using synthetic spectra of the primary peaks showed that the presence of highly overlapped peaks centered within 2 eV of each other cannot be distinguished without the presence of additional cross-peaks. The maps have therefore confirmed the existence of three dominant oxidation states, and identified positions of UIV, UV and UVI U4f primary peaks and satellite structures that are consistent with previous peak-fitting efforts. Satellite structures also showed out-of-phase correlations among the different oxidation states, further confirming their use as reliable indicators of oxidation state.

Beam Damage of Poly(vinyl chloride) [PVC] Film as Observed by X-ray Photoelectron Spectroscopy

XPS spectra of a spin-coated film poly(vinyl chloride)(PVC) were collected over a period of 243 min at 303 K to determine specimen damage during long exposures to monochromatic Al Kα x-rays. For this PVC film we measured the loss of chlorine as a function of time by rastering a focused 104.6 W, 100 μm diameter x-ray beam over a 1.4 mm × 0.2 mm area on the sample.

Stability of alkyl monolayers on chemomechanically scribed silicon to air, water, hot acid, and X-rays

Abstract We report the stability of alkyl monolayers on scribed silicon to air, water, boiling 0.1 M H 2 SO 4 , and X-rays. Monolayers (ML) were prepared by scribing silicon surfaces in the presence of 1-pentene, 1-octene, 1-decene, 1-hexadecene, 1-chlorooctane, 1-bromopentane, 1,4-dibromobutane, methyl iodide, 1-iodopentane, 1-iododecane, 1-butanol, and 1-octanol with a computer-controlled, diamond-tipped instrument. In all cases some initial oxidation of the silicon substrate was observed by X-ray photoelectron spectroscopy (XPS), which increased with time, first rapidly, and then more slowly. Oxidation appears to proceed more quickly for silicon scribed under 1-haloalkanes than 1-alkenes, and more quickly for silicon scribed under 1-haloalkanes that were stored in air than in water. In the case of silicon scribed under an iodoalkane, the resulting iodine to silicon XPS ratio decreased with time, but even after extended exposures to air or water some iodine remained on the surfaces. Steric hindrance and/or hydrophobic effects appear to influence the degree of surface oxidation and halogen loss. The C 1s/Si 2p XPS ratios of surfaces prepared from 1-alkenes and 1-haloalkanes remain nearly constant after all exposures to air, water, hot acid and X-rays. Water capacities of hydrophobic corrals were measured in a semi-automated fashion with a Gilson 215 Liquid Handler and showed trends similar to the XPS results. Hydrophobic corrals generally retained significant fractions of their capacities to hold water with time. Sample-to-sample variation in corral capacity was attributed to variation in the scribing procedure, including possible changes in tip shape. To within experimental error no change in the amount of C, O, or Br at the surfaces was observed by XPS after nearly 4 h of illumination with monochromatic Al Kα X-rays.

Manganese Dioxide (MnO2) by XPS

XPS spectra of manganese dioxide (MnO2) powder are presented. The spectra were collected using monochromated Al Kα x-rays. Spectra include survey scan, the Mn 2p, 3p, and 3s regions, the O 1s region, and the Mn LMM Auger transitions.

Rhodium and Rhodium Oxide Thin Films Characterized by XPS

RhO2 belongs to the family of conducting platinum group metal oxides, which have attracted attention as new capacitor electrode materials for dynamic random access memories (DRAMs) and nonvolatile ferroelectric random access memories (FeRAMs). Rh, Rh2O3, and RhO2 thin films were prepared by sputtering and their XPS spectra were collected with a monochromatic Al Kα x-ray source. This report includes XPS spectra of Rh 3d and O 1s core regions for these films.

Characterization of Cobalt Silicide Formation by X-ray Photoelectron Spectroscopy. I. CoSi

X-ray photoelectron spectroscopy (XPS) has been used to characterize the chemical composition and chemical state information of silicide formation in our laboratory and many others. In this work, we report the x-ray photoelectron spectra of CoSi. XPS spectra were measured with the Physical Electronics Quantum2000 system using a monochromatic Al Kα x-ray source. A survey spectrum and multiplex spectra of Co and Si photoemission lines as well as Co Auger lines were recorded.

Characterization of Cobalt Silicide Formation by X-ray Photoelectron Spectroscopy. II. CoSi2

X-ray photoelectron spectroscopy (XPS) has been used to characterize the chemical composition and chemical state information of silicide formation in our laboratory and many others. In the present work, we report the x-ray photoelectron spectra of CoSi2. XPS spectra were measured with the Physical Electronics Quantum2000 system using a monochromatic Al Kα x-ray source. A survey spectrum and multiplex spectra of Co and Si photoemission lines as well as Co Auger lines were recorded.

Epitaxial TiN(001) Grown and Analyzed In situ by XPS and UPS. I. Analysis of As-deposited Layers

X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) were used to characterize as-deposited epitaxial TiN(001) layers grown in situ. The films were deposited by ultrahigh vacuum reactive magnetron sputtering on MgO(001) at 850 °C in pure N2 discharges maintained at a pressure of 5 mTorr (0.67 Pa). Mg Kα and monochromatic Al Kα x-ray sources were used to obtain the XPS spectra, while the UPS data was generated by He I and He II UV radiation. The spectra show that the TiN(001) surfaces are free of O and C. The films were found to be stoichiometric in agreement with Rutherford backscattering spectroscopy (RBS) results, yielding a N/Ti ratio of 1.02 ± 0.02.

Epitaxial ScN(001) Grown and Analyzed In situ by XPS and UPS. I. Analysis of As-deposited Layers

X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) were used to characterize as-deposited ScN(001) layers grown in situ. The films were deposited by ultrahigh vacuum reactive magnetron sputtering on MgO(001) at 800 °C in pure N2 discharges maintained at a pressure of 5 mTorr (0.67 Pa). Mg Kα and monochromatic Al Kα x-ray sources were used to obtain the XPS spectra, while the UPS data were generated by He I and He II UV radiation. The spectra show that the ScN(001) surfaces are free of O and C. The films were found to have a slight excess of nitrogen, in agreement with Rutherford backscattering spectroscopy (RBS) results, yielding a N/Sc ratio of 1.11 ± 0.03.

Epitaxial VN(001) Grown and Analyzed In situ by XPS and UPS. I. Analysis of As-deposited Layers

X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) were used to characterize as-deposited epitaxial VN(001) layers grown in situ. The films were deposited on MgO(001) at 650 °C in pure N2 discharges maintained at a pressure of 5 mTorr (0.67 Pa). Mg Kα and monochromatic Al Kα x-ray sources were used to generate the XPS spectra, while the UPS data were generated by He I and He II UV radiation. Analysis of the results show that the VN(001) surfaces are free of O and C. The films were found to be stoichiometric in agreement with Rutherford backscattering spectroscopy (RBS) results, yielding a N/V ratio of 1.06±0.02.

Third Row Transition Metals by X-ray Photoelectron Spectroscopy

XPS spectra have been obtained from 11 metals in the third row of transition elements using a Quantum 2000 Scanning ESCA Microprobe. The metals analyzed include La, Hf, Ta, W, Re, Ir, Pt, Au, Tl, Pb, and Bi. Each sample was Ar+ ion etched before XPS analysis to remove surface contamination and/or oxide. The spectra include standard survey scans and high-energy resolution scans of the photoelectron peaks, as well as selected x-ray induced Auger peaks. Each spectrum was collected using a 100 μm diameter monochromatic Al Kα x-ray beam scanned over a 1.5 mm × 0.2 mm area of each sample. Survey scans were collected using a 58.7 eV pass energy, while high energy resolution scans were collected using a 23.5 eV pass energy.

Analysis of a Filled Poly(vinyl chloride) Polymer by XPS

We report x-ray photoemission spectra for a CaCO3 filled poly(vinyl chloride) (PVC) polymer with dioctyl pthalate plasticizer. XPS spectra were acquired with a SSI model SSX-100 instrument using monochromated Al Kα x-rays. We present the survey spectrum (binding energy 0–1000 eV) and a narrow spectrum of the C 1s, O 1s, and Cl 2p photoelectron peaks.