Use of gas cluster ion source depth profiling to study the oxidation of fullerene thin films by XPS

McGettrick, James D.; Speller, Emily M.; Li, Zhe; Durrant, James R.; Watson, Trystan

doi:10.1016/j.orgel.2017.06.022

Cited by 5 publications

(4 citation statements)

References 55 publications

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“…Surface-sensitive techniques such as Secondary Ion Mass Spectrometry (SIMS), X-ray Photoelectron Spectroscopy (XPS), and Auger Electron Spectroscopy (AES) combined with ion-induced material removal can be used to create spatial maps of the chemical composition of materials in a process called depth profiling. This approach has been successfully applied to many systems both inorganic and organic. − The main problem of depth profile acquisition is the degradation of resolution with a time of analysis . There are two main factors in play here: topography development , and ion-beam-induced material alteration. ,, The latter issue is virtually solved by the introduction of large gas cluster ion beams (GCIB). − The topography development problem can be mitigated by sample rotation .…”

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confidence: 99%

Intuitive Model of Surface Modification Induced by Cluster Ion Beams

2020

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Topography development is one of the main factors limiting the quality of depth profiles during depth profiling experiments. One possible source of topography development is the formation of self-organized patterns due to cluster ion beam irradiation. In this work, we propose a simple model that can intuitively explain this phenomenon in terms of impact-induced mass transfer. By coupling our model with molecular dynamics simulations, we can predict the critical incidence angle, which separates the smoothening and roughening regimes. The results are in quantitative agreement with experiments. It is observed that the problems arising from topography development during depth profiling with cluster projectiles can be mitigated by reducing the beam incidence angle with respect to the surface normal or increasing its kinetic energy.

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confidence: 99%

Intuitive Model of Surface Modification Induced by Cluster Ion Beams

2020

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“…It is important to note that a key ingredient for the aforementioned photodegradation reactions, namely molecular oxygen, was found to diffuse tens of times faster into the interstitial voids in the fullerene lattice when irradiated with UV or visible light. , The presence of oxygen is thus expected to fuel the generation of more singlet oxygen which compounds PS degradation. Using X-ray photoelectron spectroscopy (XPS), we have previously , shown that AM1.5G light exposure leads to the detection of oxidized species in the bulk of PS–PCBM thin films rather than on just the surface in neat PS and neat PCBM films. A similar conclusion can also be reached with FTIR measurements of PS films having various PCBM loadings (0%, 20%, 80%, and 100%).…”

Section: Results and Discussionmentioning

confidence: 99%

“…8,44 The presence of oxygen is thus expected to fuel the generation of more singlet oxygen which compounds PS degradation. Using X-ray photoelectron spectroscopy (XPS), we have previously 19,45 shown that AM1.5G light exposure leads to the detection of oxidized species in the bulk of PS−PCBM thin films rather than on just the surface in neat PS and neat PCBM films. A similar conclusion can also be reached with FTIR measurements of PS films having various PCBM loadings (0%, 20%, 80%, and 100%).…”

Section: Resultsmentioning

confidence: 99%

Photoswitchable Solubility of Fullerene-Doped Polymer Thin Films

et al. 2020

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Controlling polymer film solubility is of fundamental and practical interest and is typically achieved by synthetically modifying the polymer structure to insert reactive groups. Here, we demonstrate that the addition of fullerenes or its derivatives (C60 or phenyl-C61-butyric acid methyl ester, PCBM) to polymers, followed by ultraviolet (UV) illumination can change the film solubility. Contrary to most synthetic polymers, which dissolve in organic solvents but not in water, the fullerene-doped polymer films (such as polystyrene) can dissolve in water yet remain stable in organic solvents. This photoswitchable solubility effect is not observed in either film constituents individually and is derived from a synergy of photochemistries. First, polymer photooxidation generates macroradicals which cross-link with radical-scavenging PCBM, thereby contributing to the films’ insolubility in organic solvents. Second, light exposure enhances polymer photooxidation in the presence of PCBM via the singlet oxygen pathway. This results in polymer backbone scission and formation of photooxidized products which can form hydrogen bonds with water, both contributing to water solubility. Nevertheless, the illuminated doped polymer thin films are mechanically robust, exhibiting significantly increased modulus and density compared to their pristine counterpart, such that they can remain intact even upon sonication in conventional organic solvents. We further demonstrate the application of this solubility-switching effect in dual tone photolithography, via a facile, economical, and environmentally benign solution-processing route made possible by the photoactive nature of polymer–PCBM thin films.

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“…Further analysis of the optimized PCBM layer was carried out using XPS, to determine if any degradation of the surface layer had occurred. This would be expected to be indicated by oxidation of the PCBM molecules and an increase in the oxygen levels detected in the film 50 . Two main O(1s) features due to the ether like and carbonyl oxygen atoms in the ester group of the PCBM side chain are expected to be present in the XPS spectra in the region of 532eV, as was found and is shown in Figure S16.…”

Section: Electron Transport Layer and Inter Layermentioning

confidence: 99%