Harmonische Zusammenarbeit: Nanopartikel aus Mn3O4 und aus Kern/Schale‐strukturiertem Rh/Cr2O3 als Cokatalysatoren auf der Oberfläche eines GaN‐ZnO‐Mischkristalls als Katalysator beschleunigen die O2‐ bzw. H2‐Entwicklung unter sichtbarem Licht (λ>420 nm) und verbessern so die Wasserspaltungsaktivität gegenüber analogen Systemen, die nur mit Mn3O4 oder Rh/Cr2O3 modifiziert wurden.
The coloading effect of H2 and O2 evolution cocatalysts on the overall water splitting reaction was investigated using a solid solution of GaN and ZnO (hereafter termed GaN:ZnO) as a photocatalyst. GaN:ZnO was modified with nanoparticulate Mn3O4, RuO2, and IrO2 as O2 evolution cocatalysts and with core/shell‐type Rh/Cr2O3 composites as H2 evolution cocatalysts. The photocatalytic activity of the coloaded samples for overall water splitting was higher than that of the samples modified with either of the O2 or H2 evolution cocatalysts alone. The activity enhancement induced by coloading was comparable for the three O2 evolution cocatalysts investigated at the optimized loading amounts. Loading of a more efficient Rh/Cr2O3 cocatalyst prepared by adsorption of Rh nanoparticles further improved the photocatalytic activity. It was concluded that a simultaneous improvement in both oxidation and reduction reactions was effective at enhancing the photocatalytic activity of GaN:ZnO, whereas the reduction reactions limited the overall reaction rate of the coloaded system more significantly.
Microstructural changes that occur in a GeSbTe film during repetitious overwriting in phase-change optical recording were investigated. The GeSbTe active layer was melted by a focused laser diode (LD) beam during each overwriting process over amorphous mark formation. The repetitious solidification and liquefaction process in such a short time as 50–200 ns resulted in microstructural changes in the active layer: a segregation, sink, and void formations. The sink was formed in the low-density active layer due to the shrinking of the volume during the resolidification process. Sink formation could be suppressed when a high-density active layer, having more than 80% of the bulk density, was used. Such a high-density GeSbTe film, however, resulted in a void formation of the size of 0.1 μm. The voids were thought to be nucleated by residual vacancies and Ar precipitation, since the active layer contained a high concentration of Ar impurities, due to the atomic peening effect. The subsequent void coalescence and migration processes across the beam scanning direction could result in the formation of thermally discontinuous grooves at the edges of the written marks. The voids could also migrate along the LD beam scanning direction, accompanied by a material flow of the active layer in the opposite direction. These phenomena were also found to depend on the material used to fabricate the protective layers which sandwiched the active layer. A TaOx protective layer enhanced the void migration across the track, resulting in the removal of voids from the center of the track. Use of the ZnS:SiO2 compound protective layer confined voids to the center of the track. The ZnS:SiO2 protective layer also promoted the formation of thermally discontinuous grooves at the edges of amorphous marks. The material flow along the track resulted in a thicker active layer at the start of the consecutive LD irradiation, and also in a high void density region at the final edge of the irradiation having a length on the order of 10 μm. This tendency was found for both the ZnS:SiO2 and TaOx sandwiching media.
As-sputtered and melt-quenched amorphous structures together with the laser-induced crystallized structure of Ge-Sb-Te thin films were investigated using high-resolution electron microscopy ͑HREM͒ and nanobeam electron diffraction ͑NBED͒. Each of the Ge-Sb-Te thin films was embedded in a four-layered stack, which is the same as the layered structure of phase-change optical disks. Cross-sectional HREM revealed crystalline atomic clusters in the melt-quenched amorphous layer at a greater frequency than in the as-sputtered amorphous layer. Autocorrelation function analysis of the HREM images revealed similarity between the structures of atomic ordered regions in the amorphous phase and that of crystalline Sb. Atomic pair-distribution functions derived from halo NBED intensity analysis indicated that the atomic neighbor correlations developed more in the melt-quenched amorphous phase than in the as-sputtered phase. The development of locally ordered regions is considered to be closely related to the differences in optical properties and crystallization behaviors between these two amorphous phases.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.