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- Haitjema, Jarich, et al.
(författare)
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Soft X-ray absorption and fragmentation of tin-oxo cage photoresists
- 2024
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Ingår i: Physical Chemistry Chemical Physics. - 1463-9076. ; 26:7, s. 5986-5998
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Tidskriftsartikel (refereegranskat)abstract
- “Tin-oxo cage” organometallic compounds are considered as photoresists for extreme ultraviolet (EUV) photolithography. To gain insight into their electronic structure and reactivity to ionizing radiation, we trapped bare gas-phase n-butyltin-oxo cage dications [(BuSn)12O14(OH)6]2+ in an ion trap and investigated their fragmentation upon soft X-ray photoabsorption by means of mass spectrometry. In complementary experiments, the tin-oxo cages with hydroxide and trifluoroacetate counter-anions were cast in thin films and studied using X-ray transmission spectroscopy. Quantum-chemical calculations were used to interpret the observed spectra. At the carbon K-edge, a distinct pre-edge absorption band can be attributed to transitions in which electrons are promoted from C1s orbitals to the lowest unoccupied molecular orbitals, which are delocalized orbitals with strong antibonding (Sn-C ?*) character. At higher energies, the most prominent resonant transitions involve C-C and C-H ?* valence states and Rydberg (3s and 3p) states. In the solid state, the onset of continuum ionization is shifted by ?5 eV to lower energy with respect to the gas phase, due to the electrostatic effect of the counterions. The O K-edge also shows a pre-edge absorption, but it is devoid of any specific features, because there are many transitions from the different O1s orbitals to a large number of vacant orbitals. In the gas phase, formation of the parent [(BuSn)12O14(OH)6]3+ radical ion is not observed at the C K-edge nor at the O K-edge, because the loss of a butyl group from this species is very efficient. We do observe a number of triply charged photofragment ions, some of which have lost up to 5 butyl groups. Structures of these species are proposed based on quantum-chemical calculations, and pathways of formation are discussed. Our results provide insight into the electronic structure of alkyltin-oxo cages, which is a prerequisite for understanding their response to EUV photons and their performance as EUV photoresists.
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| 2. |
- Suchorski, Y., et al.
(författare)
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Surface-structure libraries: multifrequential oscillations in catalytic hydrogen oxidation on rhodium
- 2019
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:7, s. 4217-4227
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Tidskriftsartikel (refereegranskat)abstract
- Multifrequential oscillating spatiotemporal patterns in the catalytic hydrogen oxidation on rhodium have been observed in situ in the 10 -6 mbar pressure range using photoemission electron microscopy. The effect is manifested by periodic chemical waves, which travel over the polycrystalline Rh surface and change their oscillation frequency while crossing boundaries between different Rh(hkl) domains. Each crystallographically specific μm-sized Rh(hkl) domain exhibits an individual wave pattern and oscillation frequency, despite the global diffusional coupling of the surface reaction, altogether creating a structure library. This unique reaction behavior is attributed to the ability of stepped surfaces of high-Miller-index domains to facilitate the formation of subsurface oxygen, serving as a feedback mechanism of kinetic oscillations. Formation of a network of subsurface oxygen as a result of colliding reaction fronts was observed in situ. Microkinetic model analysis was used to rationalize the observed effects and to reveal the relation between the barriers for surface oxidation and oscillation frequency. Structural limits of the oscillations, the existence range of oscillations, as well as the effect of varying hydrogen pressure are demonstrated.
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