Hydrogen Gas Sensors Based On Nanosrystalline SnO2 Thin Films Grown On Different Substrates Using Sol-Gel Spin Coating Method
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Date
2017-05
Authors
Kadhim, Imad Hussein
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Publisher
Universiti Sains Malaysia
Abstract
Sol–gel spin coating is a low-temperature method (below 100 oC) and possibly the lowest cost method for growing nanocrystalline (NC) tin dioxide (SnO2) on various substrates. NC SnO2 has potential to improve the properties of gas sensor device while also significantly lowering the cost. As-deposited and annealed SnO2 thin films suffered from cracks that appeared on the surface of the SnO2 thin films and they exhibited negative response effects of device performance. Therefore, different volume ratios of glycerin (0:1, 1:12 and 1:8) are added to the sol solutions to overcome the problem of cracks. NC SnO2 thin films are grown on three different substrates, namely, bare silicon Si (100), silicon dioxide SiO2/Si, and sapphire Al2O3. The growth mechanisms for the NC SnO2 are investigated through X-ray Diffraction (XRD), field emission scanning electron microscope (FESEM), Energy Dispersive X-ray spectroscopy (EDX) and Raman spectroscopy. The best glycerin volume ratio determined is (1:12), which eliminated cracks and improved the crystallization. X-ray diffraction analysis indicated the amorphous nature of the as-deposited thin films. The samples annealed at 400 oC for 2 h in air exhibited reflection peaks that agreed with the tetragonal rutile structure of standard bulk SnO2. Increasing annealing temperatures from 400 to 600 oC resulted in improvement in the crystallization and increase in the crystallite size. In addition, we observed a reduction of strains and crystalline defects induced during growth of the film such as dislocations, which originated from the incomplete dissolving of tin (II) chloride dihydrate in pure ethanol. However, FESEM images showed the formations of agglomeration on the surface of NC SnO2 thin films when the samples were annealed at 600 oC.
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Keywords
Sol–gel spin coating is a low-temperature method , lowest cost method for growing nanocrystalline