Synthesis, Characterization and Gas Sensing Properties of SnO$_{2}$-\textit{x}Fe$_{2}$O$_{3}$(\textit{x} = 0 to 1) Thin Films

Due to special properties and enhanced performance, nanocrystalline composites are being explored for use in potential applications in gas sensors, solar energy conversion and photocatalysis. We report the properties of SnO$_{2}$ -- $x$Fe$_{2}$O$_{3}$ ($x$ = 0 to 1) nanocrystalline composite thin films grown by the spin-on metal-organic decomposition method using Fe and Sn ethyl hexanoate on sapphire substrates. The films, on annealing at 600$^{o}$C, are comprised of SnO$_{2}$ and Fe$_{2}$O$_{3}$ nanoparticles, as evidenced by X.ray diffraction and Raman spectra. Ultraviolet-visible spectra indicate a decreasing band gap of this composite from $\sim $3.9 to 2.25eV with increasing Fe$_{2}$O$_{3}$ concentration. These samples were also tested for response to CO gas in a nitrogen environment. Parameters such as annealing temperature, operating temperature and CO concentration were varied, showing an increase in sensitivity with operating temperature, and a decreasing sensitivity with increasing Fe$_{2}$O$_{3 }$concentration.