Core–shell
nanowires are an interesting and perspective
class of radially heterostructured nanomaterials where epitaxial growth
of the shell can be realized even at noticeable core–shell
lattice mismatch. In this study epitaxial hexagonally shaped shell
consisting of WS2 nanolayers was grown on {11̅00}
facets of prismatic wurtzite-structured [0001]-oriented ZnO nanowires
for the first time. A synthesis was performed by annealing in a sulfur
atmosphere of ZnO/WO3 core–shell structures, produced
by reactive dc magnetron sputtering of an amorphous a-WO3 layer on top of ZnO nanowire array. The morphology and phase composition
of synthesized ZnO/WS2 core–shell nanowires were
confirmed by scanning and transmission electron microscopy (SEM and
TEM), micro-Raman, and photoluminescence spectroscopy. Epitaxial growth
of WS2(0001) layer(s) on {11̅00} facets of ZnO nanowire
is unexpected due to incompatibility of their symmetry and structure
parameters. To relax the interfacial incoherence, we propose a model
of ZnO/WS2 interface containing WS2 bridging
groups inside and use first-principles simulations to support its
feasibility.
A comparative study of heterostructured CuO/CuWO4 core/shell nanowires and doublelayer thin films was performed through X-ray diffraction, confocal micro-Raman spectroscopy and electron (SEM and TEM) microscopies. The heterostructures were produced using a two-step process, starting from a deposition of amorphous WO3 layer on top of CuO nanowires and thin films by reactive DC magnetron sputtering and followed by annealing at 650°C in air. The second step induced a solid-state reaction between CuO and WO3 oxides through a thermal diffusion process, revealed by SEM-EDX analysis. Morphology evolution of core/shell nanowires and double-layer thin films upon heating was studied by electron (SEM and TEM) microscopies. A formation of CuWO4 phase was confirmed by X-ray diffraction and confocal micro-Raman spectroscopy.
Laser-induced damage experiments on HfO2 and Nb 2 O 5 thin films were performed with 500 fs pulse duration at 1030 nm wavelength. Threshold fluences as a function of beam size have been determined for effective beam diameters ranging from 40 to 220 µm, in single shot regime. The results suggest no beam size effect related to material properties in the investigated range, but size effects related to the metrology. The results indicate the importance of appropriate focusing conditions and beam measurement to qualify the optics for use in lasers with large beam sizes.
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