Synthesis and characterization of sol-gel derived nanocrystalline tin oxide thin film as hydrogen sensor

Tin oxide (SnOx) semiconductor thin film is coated on Pyrex glass (silica) substrates using the sol-gel dip-coating technique utilizing alkoxide precursor. The thin film is extensively characterized for its surface morphology, chemistry, thickness, and nanocrystallite size using different analytical techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and high-resolution transmission electron microscopy (HRTEM). The HRTEM sample preparation is done for the first time using focused ion-beam (FIB) milling technique. Under the given processing conditions, SnOx, semiconductor thin film having thickness 100-150 nm and nanocrystallite size 6-8 nm is obtained. In view of the reported literature and the present experimental data, it is demonstrated that the film is suitable for sensing H-2 gas at room temperature. Sensitivity value as high as 394% is observed at room temperature for 4 vol.% H-2, which is an explosive limit at room temperature for the space-based applications as set by NASA. (C) 2003 Elsevier B.V. All rights reserved.