Swiderek, Petra
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Swiderek, Petra
Official Name
Swiderek, Petra
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Swiderek, P.
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GND
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Item type:Publication, Electron-induced hydroamination of ethane as compared to ethene: implications for the reaction mechanism(Royal Society of Chemistry, 2023-12-15); ; ; The properties of carbonaceous materials with respect to various applications are enhanced by incorporation of nitrogen-containing moieties like, for instance, amino groups. Therefore, processes that allow the introduction of such functional groups into hydrocarbon compounds are of utmost interest. Previous studies have demonstrated that hydroamination reactions which couple amines to unsaturated sites within hydrocarbon molecules do not only proceed in the presence of suitably tailored catalysts but can also be induced and controlled by electron irradiation. However, studies on electron-induced hydroaminations so far were guided by the hypothesis that unsaturated hydrocarbons are required for the reaction while the reaction would be much less efficient in the case of saturated hydrocarbons. The present work evaluates the validity of this hypothesis by post-irradiation thermal desorption experiments that monitor the electron energy-dependent yield of ethylamine after electron irradiation of mixed C2H4:NH3 and C2H6:NH3 ices with the same composition and thickness. The results reveal that, in contrast to the initial assumption, ethylamine is formed with similar efficiency in both mixed ices. From the dependence of the product yields on the electron energy, we conclude that the reaction in both cases is predominantly driven by electron ionization of NH3. Ethylamine is formed via alternative reaction mechanisms by which the resulting NH2˙ radicals add to C2H4 and C2H6, respectively. The similar efficiency of amine formation in unsaturated and saturated hydrocarbons demonstrates that electron irradiation in the presence of NH3 is a more versatile tool for introducing nitrogen into carbonaceous materials than previously anticipated.journal articleBand:26Heft:363 55 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Water-Assisted Process for Purification of Ruthenium Nanomaterial Fabricated by Electron Beam Induced Deposition(American chemical society, 2020-08-04); ; ; ; The purity of nanomaterials fabricated by focused electron beam induced deposition (FEBID) is often not high enough for the desired application. For instance, large amounts of carbon incorporated into the deposits deteriorate their electrical conductivity. Such impurities stem from incomplete electron-induced fragmentation of the applied precursors. Except for nanomaterials containing the most noble and thus oxidation-resistant metals, deposits cannot be purified by harsh post-processing steps like O2 treatment, and excessive thermal annealing is detrimental to the desired shape fidelity. Milder purification protocols based on electron irradiation in the presence of H2O vapor have thus been developed, and it was demonstrated that they yield pure Pt and Au deposits. Herein, we report on the application of such a water-assisted purification strategy to deposits produced from the FEBID precursor bis(ethylcyclopentadienyl)ruthenium(II) ((EtCp)2Ru). Such Ru nanomaterials are relevant to the repair of masks for extreme ultraviolet lithography. In contrast to noble metals, where higher doses lead to higher purity, and contrary to purification using O2 that is accompanied by a continuous increase of the oxygen content, we here demonstrate the existence of an ideal purification dose for Ru-based FEBID materials, where oxidation is kept at a minimum, while carbon is effectively removed from the deposits. In addition, a complementary surface study under ultrahigh vacuum conditions provides insights into the chemistry that transforms the carbonaceous contamination into CO. The results provide evidence that water-assisted purification can be applied to a wider range of FEBID deposits also including those containing Ru as an example of a less noble metal.journal articleBand:3Heft:836 114 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Electron-Induced Processing of Methanol IceThe formation of methane (CH4), formaldehyde (H2CO), ethylene glycol (HOCH2CH2OH), methoxymethanol (CH3OCH2OH), dimethyl ether (CH3OCH3), and ethanol (CH3CH2OH) upon electron irradiation of condensed multilayer adsorbates of CH3OH as a model of cosmic CH3OH ice has been monitored by the combined use of electron-stimulated and thermal desorption experiments. The energy-dependent relative yields of all products were measured between 2.5 and 20 eV, and the reaction mechanisms of product formation were deduced. The energy dependences of the yields of HOCH2CH2OH, CH3OCH2OH, CH3OCH3, and CH3CH2OH agree closely with their threshold at the lowest electronic excitation energy of CH3OH. The formation of these products is consequently ascribed to the reactions of radicals formed by the dissociation of neutral electronically excited states and, at higher energy, also by ionization and subsequent proton transfer to an adjacent CH3OH. These electron–molecule interactions also can contribute to the nonresonant formation of H2CO and CH4; these latter products are also produced through resonances around 4 eV reported previously from anion electron-stimulated desorption (ESD) experiments and around 13 eV seen earlier in the energy-dependent yield of carbon monoxide (CO). The present results constitute the most complete data set on the energy dependence of product formation during low-energy electron exposure of condensed CH3OH so far. They provide a comprehensive picture of the reactions triggered by electron impact with energies in the range between 2.5 and 20 eV as representative of low-energy secondary electrons that are released from condensed material, for instance, under the effect of cosmic radiation.journal articleBand:5Heft:244 44 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Controlling electron beam induced deposition of iron from Fe(CO)5: Inhibition of autocatalytic growth by NH3 and reactivation by electron irradiation(American Vacuum Society, 2023-04-13); ; ; Focused electron beam induced deposition (FEBID) is a versatile direct-write approach to produce nanostructures from organometallic precursor molecules. Ideally, the material is deposited only when precursors interact with and are dissociated by the impinging electrons so that the process is spatially defined by the electron beam. In reality, however, thermal surface reactions as known from chemical vapor deposition can also contribute to the dissociation of the precursors. They often produce material with higher purity but can also impair the spatial selectivity of the electron-induced deposit growth. This work aims at an approach to suppress such thermal chemistry and to re-enable it within an area defined by the electron beam. We have, thus, used a surface science approach to study the inhibition of autocatalytic growth (AG) of Fe from Fe(CO)5 by NH3 and the reactivation of AG on the surface by electron irradiation. The experiments were performed under ultrahigh vacuum conditions using thermal desorption spectrometry to characterize adsorption and reactivity of Fe(CO)5 on Fe seed layers that were prepared by dosing Fe(CO)5 during electron irradiation of the entire sample surface (referred to as EBID herein). Auger electron spectroscopy was used to monitor deposit growth and to reveal the potential inhibition of AG by NH3 as well as the reactivation of the surface by electron irradiation. The results show that adsorption of NH3 slows down AG on deposits prepared by EBID but not on Fe layers produced by AG. Electron irradiation after adsorption of NH3 reactivates the surface and thus re-establishes AG. We propose that co-injection of NH3 during FEBID from Fe(CO)5 could be a viable strategy to suppress unwanted AG contributions and, therefore, enhance the spatial control of the deposition process.journal articleBand:41Heft:367 74