We reported the fabrication of a highly sensitive and fast switchable humidity sensor based on ZnO-TiO 2 core-shell nanorods that were synthesized using hydrothermal solution and atomic layer deposition. These nanorods were thermally treated under various physical conditions to improve their sensing performance.The structural investigation revealed that the crystal and microstructure changed with the thermal treatment. Notably, the amorphous TiO 2 shell layer transformed into various degrees of crystalline phase after annealing in air and a vacuum at 400 C. Furthermore, the responses of the sensors fabricated from the ZnO-TiO 2 nanorods, with and without thermal annealing, to relative humidity (RH) changes were proportional with the increase in humidity. Among various samples, ZnO-TiO 2 nanorods thermally treated in a vacuum exhibited the highest humidity selectivity in response to the cyclic changes in humidity from 11% RH to 33-95% RH at room temperature. Possible mechanisms for the enhancement of sensor performance have been discussed based on structural modifications caused by the thermal treatments.
(La,Sr)MnO3 (LSMO) nanolayers with various crystallographic textures were grown on the sapphire substrate with and without In2O3 epitaxial buffering. The LSMO nanolayer with In2O3 epitaxial buffering has a (110) preferred orientation. However, the nanolayer without buffering shows a highly (100)-oriented texture. Detailed microstructure analyses show that the LSMO nanolayer with In2O3 epitaxial buffering has a high degree of nanoscale disordered regions (such as subgrain boundaries and incoherent heterointerfaces) in the film. These structural inhomogeneities caused a low degree of ferromagnetic ordering in LSMO with In2O3 epitaxial buffering, which leads to a lower saturation magnetization value and Curie temperature, and higher coercivity and resistivity.
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