Integration of emerging complex-oxide compounds into sophisticated nanoscale single-crystal geometries faces significant challenges arising from the kinetics of vapor-phase thin-film epitaxial growth. A comparison of the crystallization of the model perovskite SrTiO (STO) on (001) STO and oxidized (001) Si substrates indicates that there is a viable alternative route that can yield three-dimensional epitaxial synthesis, an approach in which STO is crystallized from an amorphous thin film by postdeposition annealing. The crystallization of amorphous STO on single-crystal (001) STO substrates occurs via solid-phase epitaxy (SPE), without nucleation and with a temperature-dependent amorphous/crystalline interface velocity. In comparison, the crystallization of STO on SiO/(001) Si substrates requires nucleation, resulting in a polycrystalline film with crystal sizes on the order of 10 nm. A comparison of the temperature dependence of the nucleation and growth processes for these two substrates indicates that it will be possible to create crystalline STO materials using low-temperature crystallization from a crystalline seed, even in the presence of interfaces with other materials. These processes provide a potential route for the formation of single crystals with intricate three-dimensional nanoscale geometries.

Doped and undoped zinc oxide fibers were fabricated by electrospinning at various solution flow rates of 2, 4, and 6 ll/min followed by sintering at 550 C. The nanogenerators (NGs) fabricated from the fibers were examined for their performance by applying loads (0.25-1.5 kg) representing fingers taps on the keyboard. A higher solution flow rate resulted in a larger fiber diameter, thus reducing nanogenerator voltage. The maximum power density for undoped zinc oxide-based and doped zinc oxide-based nanogenerators was 17.6 and 51.7 nW/cm 2 , respectively, under a load of 1.25 kg. Enhancing nanogenerator stability is a topic that should be investigated further.

The compatibility between natural dyes and semiconductors to produce a good performance of dye-sensitized solar cells plays an important role. The dyes from papaya leaves, mangosteen pericarps, beetroots, and N719 were investigated as sensitizers in the ZnO nanorods-based dye-sensitized solar cells. The ZnO film-coated fluorine-doped tin oxide glass substrates were prepared using a doctor blade method, followed by sintering at 450 °C. Meanwhile, the counter electrode contained of chemically deposited catalytic platinum coating. The working electrodes were first immersed in the N719 dye solution and the respective natural dye solutions at corresponding concentrations of 8 g/100 mL and 21 g/100 mL. The absorptance spectra of the dyes and dye-loaded semiconductor-working electrode were obtained by UV-Vis spectroscopy. In addition, the Fourier transform infrared spectroscopy was used to determine the characteristic functionalities of the dye molecules. Furthermore, N719-based DSSC displayed the highest efficiency (0.47%) whereas papaya leaf-based DSSC achieved the highest efficiency (0.17%) amongst the studied natural dye-based DSSCs. The improved efficiency noted in the natural dye-based DSSC was attributed to the increased current density value. The high absorptance and low electrical resistance of the DSSC loaded with papaya leaf-based dye (concentration: 8 g/100 mL) contributed to the high generated current density value. However, further studies are required to improve the fill factor properties of these solar cells that were < 33%.

Low-temperature solid-phase epitaxy is a promising route for the synthesis of thin films of ScAlMgO 4 , a compound with lattice spacings close to compound semiconductors for which there are no practical lattice-matched bulk substrates. Amorphous ScAlMgO 4 films deposited by sputtering on c-plane sapphire, Al 2 O 3 (0001), were crystallized by subsequent heating. Crystallization at 950 °C resulted in the formation of epitaxial ScAlMgO 4 from the initially amorphous layer over a period of 10 h. The epitaxial film exhibits an epitaxial arrangement in which ScAlMgO 4 [0001] is parallel to Al 2 O 3 [0001] and ScAlMgO 4 [1120] is parallel to Al 2 O 3 [1120]. The as-deposited ScAlMgO 4 films had a nonstoichiometric composition, and thus regions of MgAl 2 O 4 were produced during crystallization at 950 °C. Crystallization at a higher temperature, 1400 °C, resulted in unfavorable solid-state reactions between the thin film and the substrate, producing MgAl 2 O 4 and ScAlO 3 .

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