This paper introduces a strategy for improving the sensitivity of a gas sensor to NO2 gas. The gas sensor was fabricated using urchin-like ZnO nanostructures grown on MgO particles via vapor-phase growth and decorated with MgZnO nanoparticles via a sol-gel process. The urchin-like ZnO gas sensor decorated with MgZnO showed higher sensitivity to NO2 gas than a pristine urchin-like ZnO gas sensor. When ZnO and MgZnO form a heterojunction, a two-dimensional electron gas is generated. This improves the performance of the fabricated gas sensor. The growth morphology, atomic composition, and phase structure were confirmed through field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction, respectively.

A strategy for improving the sensitivity of a sensor for detecting CO and NH3 gases is presented herein. The gas sensor was fabricated from ZnO metal oxide semiconductor nanostructures grown via a vapor–liquid–solid process and decorated with α-Fe2O3 nanoparticles via a sol–gel process. The response was enhanced by the formation of an α-Fe2O3/ZnO n–n heterojunction and the growth of thinner wires. ZnO nanowires were grown on indium–tin–oxide glass electrodes using Sn as a catalyst for growth instead of Au. The structure and elemental composition were investigated using field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The gas sensing results indicate that the response value to 100 ppm CO was 18.8 at the optimum operating temperature of 300 °C.

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The effect of ambient gas in the sealing process on the field emitter array ͑FEA͒ was analyzed. The FEAs which consist of tips with 1 m height, 1.1 m width, and gate holes with 1 m diameter, were fabricated and these array samples were baked in Ar, N 2 , and vacuum with the same temperature condition of 470°C for 24 min. After this treatment, the measurements of the electron emission current were carried out for each sample and it was found that there was no difference between before and after baking in each sample. Also, the pieces of glass coated with Mo film of 500 Å were baked in the same condition with the arrays. Auger electron spectroscopy ͑AES͒ depth profiling and x-ray photoelectron spectroscopy analysis were performed with these samples. From AES analysis, it was found that the same depth of Mo oxide layer was formed on the surfaces of every sample.