The use of renewable electricity to prepare materials and fuels from abundant molecules offers a tantalizing opportunity to address concerns over energy and materials sustainability. The oxygen evolution reaction (OER) is integral to nearly all material and fuel electrosyntheses. However, very little is known about the structural evolution of the OER electrocatalyst, especially the amorphous layer that forms from the crystalline structure. Here, we investigate the interfacial transformation of the SrIrO3 OER electrocatalyst. The SrIrO3 amorphization is initiated by the lattice oxygen redox, a step that allows Sr2+ to diffuse and O2− to reorganize the SrIrO3 structure. This activation turns SrIrO3 into a highly disordered Ir octahedral network with Ir square-planar motif. The final SryIrOx exhibits a greater degree of disorder than IrOx made from other processing methods. Our results demonstrate that the structural reorganization facilitated by coupled ionic diffusions is essential to the disordered structure of the SrIrO3 electrocatalyst.

We investigated the oxidation of CO on PdO(101) using temperature-programmed reaction spectroscopy (TPRS), reflection absorption infrared spectroscopy (RAIRS), and density functional theory (DFT). We find that about 71% of the CO molecules adsorbed in a saturated layer on PdO(101) transform to CO2 during TPRS, with the CO2 desorbing in two main features centered at 330 and 520 K. RAIRS shows that CO molecules initially adsorb in an atop configuration on coordinatively unsaturated (cus) Pd sites of PdO(101) located next to Ocus atoms, yielding a RAIRS peak at 2135 cm–1, and that the oxidation of these species produces the CO2 TPRS peak at 330 K. Concurrent with reaction, a large fraction of CO molecules migrates to atop-Pdcus sites located next to Ocus atom vacancies (Ov) that are created during reaction, as evidenced by the appearance of a RAIRS peak centered at ∼2085 cm–1. Our RAIRS measurements demonstrate that oxidation of the CO-Pdcus/Ov species is responsible for the CO2 TPRS peak at 520 K, and further show that oxygen atoms from the subsurface readily fill Ov sites as CO molecules vacate the Pdcus/Ov sites above about 400 K. DFT calculations show that a strong enhancement in binding (∼70 kJ/mol) is responsible for the rapid migration of CO molecules from Pdcus/Ocus sites to Pdcus/Ov sites as the PdO(101) surface is reduced at low temperature. DFT also predicts that both CO species can access facile pathways for oxidation on PdO(101) via reaction with Ocus atoms, wherein the apparent reaction barriers are nearly identical in each pathway.

Organotin photoresists have shown promise for next-generation lithography because of their high extreme ultraviolet (EUV) absorption cross sections, their radiation sensitive chemistries, and their ability to enable highresolution patterning. To better understand both temperatureand radiation-induced reaction mechanisms, we have studied a model EUV photoresist, which consists of a charge-neutral butyl−tin cluster. Temperature-programmed desorption (TPD) showed very little outgassing of the butyl−tin resist in ultrahigh vacuum and excellent thermal stability of the butyl groups. TPD results indicated that decomposition of the butyl−tin resist was first order with a fairly constant decomposition energy between 2.4 and 3.0 eV, which was determined by butyl group desorption. Electron-stimulated desorption (ESD) showed that butyl groups were the primary decomposition product for electron kinetic energies expected during EUV exposures. X-ray photoelectron spectroscopy was performed before and after low-energy electron exposure to evaluate the compositional and chemical changes in the butyl−tin resists after interaction with radiation. The effect of molecular oxygen during ESD experiments was evaluated, and it was found to enhance butyl group desorption during exposure and resulted in a significant increase in the ESD cross section by over 20%. These results provide mechanistic information that can be applied to organotin EUV photoresists, where a significant increase in photoresist sensitivity may be obtained by varying the ambient conditions during EUV exposures.

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Dodecameric (Sn ) and hexameric topologies dominate monoalkyltin-oxo cluster chemistry. Their condensation, triggered by radiation exposure, recently produced unprecedented patterning performance in EUV lithography. A new cluster topology was crystallized from industrial n-BuSnOOH, and additional characterization techniques indicate other clusters are present. Single-crystal X-ray analysis reveals a β-Keggin cluster, which is known but less common than other Keggin isomers in polyoxometalate and polyoxocation chemistry. The structure is formulated [NaO (BuSn) (OH) (O) (OCH ) (Sn(H O) )] (β-NaSn ). SAXS, NMR, and ESI MS differentiate β-NaSn , Sn , and other clusters present in crude "n-BuSnOOH" and highlight the role of Na as a template for alkyltin Keggin clusters. Unlike other alkyltin clusters that are cationic, β-NaSn is neutral. Consequently, it stands as a unique model system, absent of counterions, to study the transformation of clusters to films and nanopatterns.

Carbon contamination is a notorious issue that has an enormous influence on surface science experiments, especially in near-atmospheric conditions. While it is often mentioned in publications when affecting an experiment’s results, it is more rarely analyzed in detail. We performed ambient-pressure x-ray photoelectron spectroscopy experiments toward examining the build-up of adventitious carbon species (both inorganic and hydrocarbons) on a clean and well-prepared surface using large-scale (50 × 10 mm2) rutile TiO2(110) single crystals exposed to water vapor and liquid water. Our results highlight how various factors and environmental conditions, such as beam illumination, residual gas pressure and composition, and interaction with liquid water, could play roles in the build-up of carbon on the surface. It became evident that beam-induced effects locally increase the amount of carbon in the irradiated area. Starting conditions that are independent of light irradiation determine the initial overall contamination level. Surprisingly, the rate of beam-induced carbon build-up does not vary significantly for different starting experimental conditions. The introduction of molecular oxygen in the order of 10 mbar allows for fast surface cleaning during x-ray illumination. The surface carbon contamination can be completely removed when the oxygen partial pressure is comparable to the partial pressure of water vapor in the millibar pressure range, as was tested by exposing the TiO2(110) surface to 15 mbar of water vapor and 15 mbar of molecular O2 simultaneously. Furthermore, our data support the hypothesis that the progressive removal of carbon species from the chamber walls by competitive adsorption of water molecules takes place following repeated exposure to water vapor. We believe that our findings will be useful for future studies of liquid-solid interfaces using tender x rays, where carbon contamination plays a significant role.

Solution-based organometallic nanoclusters are unique nanoscale precursors due to the ability to precisely control their size, shape, structure, and assembly. The interaction of extreme ultraviolet (EUV) or X-ray photons with these organometallic nanoclusters can result in processes that can lead to a change in solubility. This makes these materials prime candidates for nextgeneration photoresists for EUV nanolithography. In this study, we investigate the interaction of X-ray radiation with a charge neutral, sodium templated, butyl-tin Keggin (β-NaSn 13 ) nanocluster. This nanocluster is used as a model EUV photoresist to better understand the radiation induced solubility transition. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) was used to characterize the β-NaSn 13 thin films, where Sn 3d, O 1s, and C 1s core levels were measured under a range of ambient conditions, including ultrahigh vacuum and 1 mbar of oxygen, water, methanol, or nitrogen. A photon dose array was obtained for each ambient condition to determine their effect on the photon induced chemistries which result in the solubility transition. The resulting contrast curves indicate that an oxygen ambient significantly reduces the required photon dose for the solubility transition relative to UHV, while all other ambients increase the required photon dose for the solubility transition relative to UHV. We performed in situ XPS after postexposure annealing β-NaSn 13 thin films in multiple ambients to study the chemistry that occurs after a postexposure bake (PEB). The β-NaSn 13 thin films retained a significant amount of aliphatic carbon following the PEB in all the ambients we studied. On the basis of our studies, we propose that the solubility transition for β-NaSn 13 thin films occurs through radical hydrogen abstraction and radical−radical coupling reactions. These studies further improve the understanding of photon induced chemistries in a β-NaSn 13 model resist and provide mechanistic insights for EUV lithography processing with organometallic nanomaterials.

Advances in extreme ultraviolet (EUV) photolithography require the development of next-generation resists that allow high-volume nanomanufacturing with a single nanometer patterning resolution. Organotin-based photoresists have demonstrated nanopatterning with high resolution, high sensitivity, and low-line edge roughness. However, very little is known regarding the detailed reaction mechanisms that lead to radiation-induced solubility transitions. In this study, we investigate the interaction of soft Xray radiation with organotin clusters to better understand radiation-induced chemistries associated with EUV lithography. Butyltin Keggin clusters (β-NaSn 13 ) were used as a model organotin photoresist, and characterization was performed using ambient-pressure X-ray photoelectron spectroscopy. The changes in relative atomic concentrations and associated chemical states in β-NaSn 13 resists were evaluated after exposure to radiation for a range of ambient conditions and photon energies. A significant reduction in the C 1s signal versus exposure time was observed, which corresponds to the radiation-induced homolytic cleavage of the butyltin bond in the β-NaSn 13 clusters. To improve the resist sensitivity, we evaluated the effect of oxygen partial pressure during radiation exposures. We found that both photon energy and oxygen partial pressure had a strong influence on the butyl group desorption rate. These studies advance the understanding of radiation-induced processes in β-NaSn 13 photoresists and provide mechanistic insights for EUV photolithography.