This paper reports the synthesis of alkali-free layered nickel oxides with a highly swollen hydrate structure, derived from NaNiO2 through soft-chemical processes involving oxidation with bromine and subsequent acid treatment. Complete removal of interlayer Na+ ions and subsequent hydration yielded a single phase of H
x
NiO2·nH2O (x < 1, n ∼1) with an enlarged basal spacing of 9.6 Å. The materials had a monoclinic structure (C2/m); unit cell parameters for a typical composition of H0.66NiO2·0.9H2O were a = 4.8993(8) Å, b = 2.8256(4) Å, c = 9.7598(9) Å, and β = 98.88(2)°. Rietveld refinement revealed that the structure was composed of pseudohexagonal NiO2 sheets accommodating partially occupied three layers of H2O molecules and H3O+ ions in the galleries. The highly expanded layered structure is analogous to Na0.3NiO2·1.3H2O and other layer oxides such as buserite-type manganese oxide and superconducting Na
x
CoO2·yH2O but differs in alkali-free composition. The 9.6 Å phase underwent partial dehydration to give a basal spacing of 7 Å upon exposure to atmosphere with a relative humidity of <30%.
Magneto-optical Faraday effect has been investigated for 3d-transition-metal-substituted titania nanosheets Ti1−xMxO2 (M=Fe,Co). In Ti0.8Co0.2O2 and Ti0.6Fe0.4O2 nanosheets, a strong magneto-optical response (∼104deg∕cm) appeared near the absorption edge at 260nm. We find that tailoring magneto-optical properties could be achieved by (Fe∕Co) cosubstitution and an optimally doped Ti0.75Fe0.1Co0.15O2 nanosheet exhibits a gigantic magneto-optical response (∼105deg∕cm) over the wide wavelength region (400–750nm). By analyzing electronic structures from first-principle calculations, we have clarified that the d-d transitions are responsible for the gigantic signal in (Fe∕Co)-cosubstituted nanosheets.
We have developed a high-mobility and high-processability oxide semiconductor using amorphous In2O3–SnO2–ZnO (a-ITZO) as the channel material. An a-ITZO thin-film transistor (TFT) was fabricated by a back-channel-etch process. Its field effect mobility was more than 20 cm2 V-1 s-1 and its subthreshold swing was 0.4 V s-1, which makes it a promising candidate for next-generation TFTs.
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