Depth Profiling of Organic Films with X-ray Photoelectron Spectroscopy Using C60+ and Ar+ Co-Sputtering

Yu, Bang-Ying; Chen, Yingyu; Wang, Wei-Ben; Hsu, Ming-Hung; Tsai, Shu-Ping; Lin, Wei–Chun; Lin, Yao; Jou, Jwo-Huei; Chu, Chia‐Chi; Shyue, Jing‐Jong

doi:10.1021/ac702626n

Cited by 63 publications

(52 citation statements)

References 9 publications

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“…Sputter depth profiling with energetic Ar-ions (4 keV) provided some information (Figures S7-S10), but information from the C 1s region is of limited use as the bombardment of carbon films is known to cause some chemical changes to the carbon morphologies. 54,55 Additionally, differential charging observed in the synchrotron-based XPS studies support the electrically resistive nature of the Al oxyfluoride (Al-O-F) formed during cycling in the LiClO 4 electrolyte.…”

Section: Discussionmentioning

confidence: 69%

XPS Investigation of the Electrolyte Induced Stabilization of LiCoO₂and “AlPO₄”-Coated LiCoO₂Composite Electrodes

Quinlan

Kwabi

et al. 2015

J. Electrochem. Soc.

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The "AlPO 4 " coating has been shown to improve the electrochemical performance of LiCoO 2 batteries. We previously showed that the "AlPO 4 " coating promotes the formation of metal fluorides, which could act as a stable surface film and protect LiCoO 2 from continuous degradation upon cycling. In this work, we removed the fluorine source in the LiPF 6 salt by using the LiClO 4 salt and investigated the effectiveness of the "AlPO 4 " coating. Interestingly, the "AlPO 4 " coating was found to improve the voltage efficiency and capacity retention when cycling in the LiPF 6 electrolyte, but was detrimental when cycling in the LiClO 4 electrolyte. XPS revealed that the "AlPO 4 " coating promotes the formation of metal fluoride in both electrolytes, with the surface film formed in LiClO 4 being more electrically resistive compared to that formed in LiPF 6 . The source of fluorine in the coated electrode cycled in LiPF 6 is largely attributed to the LiPF 6 salt whereas the source of fluorine in the coated electrode cycled in LiClO 4 is the binder PVDF. We believe that the coating could react with HF impurity in the LiPF 6 electrolyte or from the binder PVDF and form stable metal fluoride films on the surface. Lithium cobalt oxide, LiCoO 2 , is currently the most common cathode material used in lithium ion battery technology, 1,2 but only half of the theoretical capacity, ≈140 mA h g −1 , is obtained when charged to 4.2 V vs. Li + /Li. Higher capacity is obtainable if cycled to voltages greater than 4.2 V, but this was shown to result in high capacity loss.3,4 Structural instability 3,5 and reactivity of the cathode with the electrolyte 3 have both been proposed as possible mechanisms for the observed capacity fade. Surface modification via coatings with intrinsic materials by thermal treatment during the synthesis process 6 or with extrinsic materials, 7-10 is one successful method of improving performance. These cathodes with surface-modified LiCoO 2 1,2,6-11 have shown improvement when cycled to high voltages compared to bare LiCoO 2 positive electrodes. However, the origin responsible for the increased performance is not well understood. Understanding the mechanism responsible for the enhancement in cycling stability provided by the coatings/surface modification is essential to further stabilize positive electrode materials for applications that demand high cycle life such as electrical vehicles and stationary storage.Enhanced performance in cycling associated with surface coating has been attributed to phase transitions, 3,4,[12][13][14][15] The recent investigation by Dahèron et al.,18 showed that the substitution of Al for Co not only increases the ionic nature of the Co-O bond through orbital mixing, but also that the substitution reduces the basicity of the LiCoO 2 surface, thus making the surface less receptive or vulnerable to acidic attack in the electrolyte. However, this benefit can be temporary as recent work indicates that the Li-Al-Co-O surface region is consumed during cycling. 27 The "AlPO 4 "-coati...

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Section: Discussionmentioning

confidence: 69%

XPS Investigation of the Electrolyte Induced Stabilization of LiCoO₂and “AlPO₄”-Coated LiCoO₂Composite Electrodes

Quinlan

Kwabi

et al. 2015

J. Electrochem. Soc.

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“…Recent evidence suggests that co-sputtering with C þ 60 and other ion beams, such as Ar þ can prevent the accumulation of damage associated with carbon deposition in the source (Yu et al, 2008), where it has been shown that C þ 60 =Ar þ co-sputtering can be used to extend the depth profile range and maintain a more constant sputter rate in polymer depth profiles. The theory is that the Ar þ gun prevents the deposition of carbon and therefore can both improve the quality of the depth profile and increase the achievable erosion depth.…”

Section: Co-sputteringmentioning

confidence: 99%

Cluster secondary ion mass spectrometry of polymers and related materials

Mahoney

2009

Mass Spectrometry Reviews

283

329

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Cluster secondary ion mass spectrometry (cluster SIMS) has played a critical role in the characterization of polymeric materials over the last decade, allowing for the ability to obtain spatially resolved surface and in-depth molecular information from many polymer systems. With the advent of new molecular sources such as C(60)(+), Au(3)(+), SF(5)(+), and Bi(3)(+), there are considerable increases in secondary ion signal as compared to more conventional atomic beams (Ar(+), Cs(+), or Ga(+)). In addition, compositional depth profiling in organic and polymeric systems is now feasible, without the rapid signal decay that is typically observed under atomic bombardment. The premise behind the success of cluster SIMS is that compared to atomic beams, polyatomic beams tend to cause surface-localized damage with rapid sputter removal rates, resulting in a system at equilibrium, where the damage created is rapidly removed before it can accumulate. Though this may be partly true, there are actually much more complex chemistries occurring under polyatomic bombardment of organic and polymeric materials, which need to be considered and discussed to better understand and define the important parameters for successful depth profiling. The following presents a review of the current literature on polymer analysis using cluster beams. This review will focus on the surface and in-depth characterization of polymer samples with cluster sources, but will also discuss the characterization of other relevant organic materials, and basic polymer radiation chemistry.

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“…This has been performed for instance on OLED systems, in which the metallic cathode is removed mechanically before the organic layers analysis [16]. Another approach consists on switching ion sources while crossing hybrid interfaces (e.g., using a monoatomic Ar source on inorganic layers, then switching to Argon cluster ion beams in the organic layers [17]). Finally, hybrid depth profiling with only one source has been attempted on 1.4 to 3.5 nm gold layer embedded in cholesterol deposits [14], sputtered with C 60 + ion source.…”

Section: Introductionmentioning

confidence: 99%

Hybrid Organic/Inorganic Materials Depth Profiling Using Low Energy Cesium Ions

Noël

Houssiau

2016

J. Am. Soc. Mass Spectrom.

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Abstract. The structures developed in organic electronics, such as organic light emitting diodes (OLEDs) or organic photovoltaics (OPVs) devices always involve hybrid interfaces, joining metal or oxide layers with organic layers. No satisfactory method to probe these hybrid interfaces physical chemistry currently exists. One promising way to analyze such interfaces is to use in situ ion beam etching, but this requires ion beams able to depth profile both inorganic and organic layers. Mono-or diatomic ion beams commonly used to depth profile inorganic materials usually perform badly on organics, while cluster ion beams perform excellently on organics but yield poor results when organics and inorganics are mixed. Conversely, low energy Cs + beams (<500 eV) allow organic and inorganic materials depth profiling with comparable erosion rates. This paper shows a successful depth profiling of a model hybrid system made of metallic (Au, Cr) and organic (tyrosine) layers, sputtered with 500 eV Cs + ions. Tyrosine layers capped with metallic overlayers are depth profiled easily, with high intensities for the characteristic molecular ions and other specific fragments. Metallic Au or Cr atoms are recoiled into the organic layer where they cause some damage near the hybrid interface as well as changes in the erosion rate. However, these recoil implanted metallic atoms do not appear to severely degrade the depth profile overall quality. This first successful hybrid depth profiling report opens new possibilities for the study of OLEDs, organic solar cells, or other hybrid devices.

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Depth Profiling of Organic Films with X-ray Photoelectron Spectroscopy Using C₆₀⁺ and Ar⁺ Co-Sputtering

Cited by 63 publications

References 9 publications

XPS Investigation of the Electrolyte Induced Stabilization of LiCoO₂and “AlPO₄”-Coated LiCoO₂Composite Electrodes

XPS Investigation of the Electrolyte Induced Stabilization of LiCoO₂and “AlPO₄”-Coated LiCoO₂Composite Electrodes

Cluster secondary ion mass spectrometry of polymers and related materials

Hybrid Organic/Inorganic Materials Depth Profiling Using Low Energy Cesium Ions

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Depth Profiling of Organic Films with X-ray Photoelectron Spectroscopy Using C60+ and Ar+ Co-Sputtering

Cited by 63 publications

References 9 publications

XPS Investigation of the Electrolyte Induced Stabilization of LiCoO2and “AlPO4”-Coated LiCoO2Composite Electrodes

XPS Investigation of the Electrolyte Induced Stabilization of LiCoO2and “AlPO4”-Coated LiCoO2Composite Electrodes

Cluster secondary ion mass spectrometry of polymers and related materials

Hybrid Organic/Inorganic Materials Depth Profiling Using Low Energy Cesium Ions

Contact Info

Product

Resources

About

Depth Profiling of Organic Films with X-ray Photoelectron Spectroscopy Using C₆₀⁺ and Ar⁺ Co-Sputtering

XPS Investigation of the Electrolyte Induced Stabilization of LiCoO₂and “AlPO₄”-Coated LiCoO₂Composite Electrodes

XPS Investigation of the Electrolyte Induced Stabilization of LiCoO₂and “AlPO₄”-Coated LiCoO₂Composite Electrodes