The commercialization of solar fuel devices requires the development of novel engineered photoelectrodes for water splitting applications which are based on redundant, cheap, and environmentally friendly materials. In the current study, a combination of titanium dioxide (TiO2) and zinc oxide (ZnO) onto nanotextured silicon is utilized for a composite electrode with the aim to overcome the individual shortcomings of the respective materials. The properties of conformal coverage of TiO2 and ZnO layers are designed on the atomic scale by the atomic layer deposition technique. The resulting photoanode shows not only promising stability but also nine times higher photocurrents than an equivalent photoanode with a pure TiO2 encapsulation onto the nanostructured silicon. Density functional theory calculations indicate that segregation of TiO2 at the ZnO surfaces is favorable and leads to the stabilization of the ZnO layers in water environments. In conclusion, the novel designed composite material constitutes a promising base for a stable and effective photoanode for the water oxidation reaction.

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We studied features of Raman scattering and the third-harmonic generation in silicon nanowire (SiNW) ensembles formed by means of chemical etching of crystalline silicon (c-Si) wafers with preliminary deposited silver nanoparticles in hydrofluoric acid. The c-Si wafers of different crystallographic orientations and doping levels were used, which results in variations of the formed nanostructure size and degree of order. For the excitation at 1064 nm the ratio of Raman scattering signals for SiNWs and those for initial c-Si wafer ranges from 2 to 5, whereas for shorter wavelengths the ratio increases for more ordered arrays of SiNWs of greater diameter and decreases for less ordered SiNW structures. The TH signals in SiNW ensembles demonstrate both fall and one- or two-orders-of-magnitude rise in comparison with c-Si depending on the structure of the SiNW ensemble. The obtained results are explained by the effect of partial light localization in SiNW ensembles.

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