Multifunkční vrstvy MoOx a MoOxNy s 2,5 < x < 3,0 a y < 0,2 připravené pomocí kontrolovaného reaktivního magnetronového naprašování s hlubokými oscilacemi

Reaktivní magnetronové naprašování s hlubokými oscilacemi, pulzní kontrolou toku reaktivního plynu a vstupem reaktivního plynu, orientovaným k substrátu a umístěným v zóně hustého plazmatu před Mo terčem, bylo použito pro nízkoteplotní (< 120 °C) přípravu vrstev MoOx a MoOxNy s 2,5 < x < 3,0 a y < 0,2. Vysvětlujeme výhody použité depoziční techniky umožňující hladkou a reprodukovatelnou kontrolu složení vrstev a tím i jejich struktury a vlastností. Speciální pozornost věnujeme silnému dopadu malého snížení x ve vrstvách MoOx a malého zvýšení y ve vrstvách MoOxNy na jejich optické a elektrické vlastnosti, které přímo souvisí s proměnnou elektronovou strukturou těchto vrstev. Diskutujeme možné aplikace těchto vrstev v oblasti solárních článků, organické elektroniky a lithium-iontových baterií.Reactive deep oscillation magnetron sputtering with a pulsed reactive gas flow control and to-substrate reactive gas injection into the high-density plasma in front of the sputtered Mo target was used for a low-temperature (< 120 °C) preparation of MoOx and MoOxNy films with 2.5 < x < 3.0 and y < 0.2. We explain the advantages of this deposition technique, allowing us to control smoothly and reproducibly the film composition and thus the film structure and properties. Special attention is paid to the strong effect of slightly decreasing x in MoOx films and slightly increasing y in MoOxNy films on their optical and electrical properties which are directly related to varying electronic structure of the films. We discuss possible applications of these films in the field of solar cells, organic electronic devices and lithium-ion batteries

Anion-mediated electronic effects in reducible oxides: Tuning the valence band of ceria via fluorine doping

Combining experimental spectroscopy and hybrid density functional theory calculations, we show that the incorporation of fluoride ions into a prototypical reducible oxide surface, namely, ceria(111), can induce a variety of nontrivial changes to the local electronic structure, beyond the expected increase in the number of Ce3+ ions. Our resonant photoemission spectroscopy results reveal new states above, within, and below the valence band, which are unique to the presence of fluoride ions at the surface. With the help of hybrid density functional calculations, we show that the different states arise from fluoride ions in different atomic layers in the near surface region. In particular, we identify a structure in which a fluoride ion substitutes for an oxygen ion at the surface, with a second fluoride ion on top of a surface Ce4+ ion giving rise to F 2p states which overlap the top of the O 2p band. The nature of this adsorbate F−–Ce4+ resonant enhancement feature suggests that this bond is at least partially covalent. Our results demonstrate the versatility of anion doping as a potential means of tuning the valence band electronic structure of ceri

Exploiting micro-scale structural and chemical observations in real time for understanding chemical conversion: LEEM/PEEM studies over CeO x –Cu(111)

Proper consideration of length-scales is critical for elucidating active sites/phases in heterogeneous catalysis, revealing chemical function of surfaces and identifying fundamental steps of chemical reactions. Using the example of ceria thin films deposited on the Cu(111) surface, we demonstrate the benefits of multi length-scale experimental framework for understanding chemical conversion. Specifically, exploiting the tunable sampling and spatial resolution of photoemission electron microscopy, we reveal crystal defect mediated structures of inhomogeneous copper–ceria mixed phase that grow during preparation of ceria/Cu(111) model systems. The density of the microsized structures is such that they are relevant to the chemistry, but unlikely to be found during investigation at the nanoscale or with atomic level investigations. Our findings highlight the importance of accessing micro-scale when considering chemical pathways over heteroepitaxially grown model systems