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

Abstract

Tin oxide (SnO x ) 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, SnO x 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.