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An inexpensive single-step carbon-assisted thermal evaporation method for the growth of SnO2-core/ZnO-shell nanostructures is described, and the ethanol sensing properties are presented. The structure and phases of the grown nanostructures are investigated by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. XRD analysis indicates that the core-shell nanostructures have good crystallinity. At a lower growth duration of 15 min, only SnO2 nanowires with a rectangular cross-section are observed, while the ZnO shell is observed when the growth time is increased to 30 min. Core-shell hierarchical nanostructures are present for a growth time exceeding 60 min. The growth mechanism for SnO2-core/ZnO-shell nanowires and hierarchical nanostructures are also discussed. The sensitivity of the synthesized SnO2-core/ZnO-shell nanostructures towards ethanol sensing is investigated. Results show that the SnO2-core/ZnO-shell nanostructures deposited at 90 min exhibit enhanced sensitivity to ethanol. The sensitivity of SnO2-core/ZnO-shell nanostructures towards 20 ppm ethanol gas at 400 °C is about ∼5-times that of SnO2 nanowires. This improvement in ethanol gas response is attributed to high active sensing sites and the synergistic effect of the encapsulation of SnO2 by ZnO nanostructures.

Thermal oxidation of 150-nm sputtered pure samarium metal film on silicon substrate has been carried out in oxygen ambient at various temperatures (600°C to 900°C) for 15 min and the effect of the oxidation temperature on the structural, chemical, and electrical properties of the resulting Sm 2 O 3 layers investigated. The crystallinity of the Sm 2 O 3 films and the existence of an interfacial layer were evaluated by x-ray diffraction (XRD) analysis, Fouriertransform infrared (FTIR) spectroscopy, and Raman analysis. The crystallite size and microstrain of Sm 2 O 3 were estimated by Williamson-Hall (W-H) plot analysis, with comparison of the former with the crystallite size of Sm 2 O 3 as calculated using the Scherrer equation. High-resolution transmission electron microscopy (HRTEM) with energy-dispersive x-ray (EDX) spectroscopy analysis was carried out to investigate the cross-sectional morphology and chemical distribution of selected regions. The activation energy or growth rate of each stacked layer was calculated from Arrhenius plots. The surface roughness and topography of the Sm 2 O 3 layers were examined by atomic force microscopy (AFM) analysis. A physical model based on semipolycrystalline nature of the interfacial layer is suggested and explained. Results supporting such a model were obtained by FTIR, XRD, Raman, EDX, and HRTEM analyses. Electrical characterization revealed that oxidation temperature at 700°C yielded the highest breakdown voltage, lowest leakage current density, and highest barrier height value.

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In this work, electrical properties of simultaneously oxidized and nitrided sputtered Zr thin film on n-type Si via N 2 O gas were systematically investigated and charge conduction mechanisms through the oxide were quantitatively analyzed. Effects of simultaneous oxidation and nitridation duration on the metal-oxide-semiconductor characteristics were reported. It was revealed that 15-min oxidized/nitrided sample showed the highest effective dielectric constant, breakdown field, and reliability. This was attributed to the thinnest interfacial layer, lowest total interface trap, effective oxide charge, and highest barrier height between conduction band edge of the oxide and semiconductor. Depending on the applied electric field and oxidation/nitridation duration, charges were conducted through the oxide via space-charge-limited conduction, Schottky emission, Poole-Frenkel emission, and Fowler-Nordheim tunneling mechanisms.

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