•New Oxides [Sn0.5Zn0.5]GaO3(ZnO)m (m=3–7) with IGZO type structure have been synthesized.•Crystal structure of [Sn0.5Zn0.5]GaO3(ZnO)3 refined from single crystal X-ray diffraction data.•Atomic Resolution HAADF scanning TEM images of [Sn0.5Zn0.5]GaO3(ZnO)3.•High Resolution EELS spectrum imaging for elemental mapping.Several members of hitherto unknown homologous compounds [Sn0.5Zn0.5]GaO3(ZnO)m (m=3–7) of the general formula ARO3(ZnO)m were prepared by solid state methods from the binary oxides in sealed Pt-tubes. UV–vis measurements confirm these compounds to be transparent oxides with an optical band gap in the UV region with Eg≈3 eV. Rietveld refinements on powder samples of [Sn0.5Zn0.5]GaO3(ZnO)m proved the compounds to be isostructural with InGaO3(ZnO)m, where In3+ on octahedral sites is replaced statistically by Sn4+ and Zn2+ in equal amounts preserving an average charge of 3+. Additionally, the structure of [Sn0.5Zn0.5]GaO3(ZnO)3 has been determined from flux-grown single crystals by X-ray diffraction (R3̅m, Z=3, a=3.2387(7) Å, c=41.78(1) Å, 19 parameters, 201 independent reflections, R1=0.047, wR2=0.074). The compound [Sn0.5Zn0.5]GaO3(ZnO)3 is isostructural with InGaO3(ZnO)3. [Sn0.5Zn0.5]GaO3(ZnO)3 was furthermore analyzed by High Angle Annular Dark Field (HAADF) scanning TEM and EELS spectroscopic imaging, supporting the structure model derived from X-ray diffraction data.HAADF TEM image of [Sn0.5Zn0.5]GaO3(ZnO)3 in a axis orientation showing the stacking sequence of cation layers with bright Sn/Zn columns and medium bright Zn/Ga columns

The widely applied metal-catalyzed growth mechanism of ZnO nanowires (NWs) is investigated by advanced methods of transmission electron microscopy and is discussed with respect to thermodynamic growth conditions. Au catalyst particles do not contain a substantial amount of Zn proving a solid Au catalyst at 1173 K growth temperature. This result is owed to the high equilibrium Zn partial pressure over Au–Zn alloys which in turn leads to a very low sticking coefficient of Zn from vapor and prevents alloying. Growth rates of ZnO NWs were measured between 5.5 nm s–1 and 36 nm s–1 as a function of oxygen partial pressure. The enhanced growth rate at higher oxygen partial pressures is explained by an increased sticking coefficient of Zn atoms at the Au catalyst. A growth mechanism is proposed which is quite different from the classic vapor–liquid–solid (VLS) mechanism: Zn alloys only in a thin surface layer at the catalyst and diffuses to the vapor–catalyst–NW triple phase line. There, together with oxygen, ZnO ledges nucleate which grow laterally to inner regions of the ZnO–Au heterointerface where Zn and oxygen can diffuse and finally promote NW growth in a rather kinetically controlled process. The geometry of the ZnO–Au interface — planar or stepped — and the associated diffusional transport properties are shown to be determined by the orientation relationship between Au and ZnO and hence by the atomic structure of the interface.

Inorganic and hybrid sols obtained from Si, Ti, Zr and Ce organometallic precursors were used to prepare single and multilayer coatings with different thicknesses. Planar step-index waveguides with different refractive indices were thus prepared by dip-coating the above sols onto commercial soda-lime glass substrates, followed by appropriate thermal annealing. The resultant coatings were characterized by transmission electron microscopy and energy dispersive X-ray spectrometry to elucidate the interface and bonding between the sol–gel derived coatings and the glass substrates. Diffusion of alkali and alkaline earth elements from the glass into the coating layer was confirmed and proposed to play a role in the coating-substrate bonding, inducing excellent optical quality planar interfaces. Optical waveguide characterization performed on a 4.15 μm thick hybrid SiO2:CeO2 (95:5) step-index waveguide yielded losses of 1.50 dB/cm.

Planar multilayer ZrO2:CeO2 slab waveguides were prepared by a sol–gel route and dip-coating technique onto commercial glass substrates. The coatings were microstructurally characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and by optical confocal microscopy. Coating thicknesses of ca. 500 nm and refractive index values of 2.069 ± 0.001 and 2.087 ± 0.001, respectively for TE and TM light polarization modes, were calculated by Dark m-line spectroscopy. This is consistent with the birefringent character of the coating, associated to the presence of anisotropic crystalline phases within the coating’s vitreous matrix. Finally, propagation losses of 0.9 ± 0.2 and 1.5 ± 0.2 dB/cm were determined by the scattered light measurement for TE and TM polarization modes, respectively.Graphical abstractPlanar multilayer ZrO2:CeO2 slab waveguides can be prepared easily by combining sol–gel and dip-coating methods on inexpensive commercial glass substrates. Tetragonal nanocrystals are found within the ca. 500 nm thick coatings, which cause the resulting waveguides to exhibit birefringence, an interesting property for the development of multifunctional devices.Highlights► Preparation of slab waveguides on sodalime glass substrates via sol–gel dipcoating. ► TEM substrate/interface coating characterization. ► Structural and optical property analysis of waveguide coatings. ► Identification of birefringence arising from the presence of anisotropic nanocrystals.