Ion beam engineering of morphological, structural and optical properties of Au/SnO2 hybrid nanostructured thin films

Hybrid nanostructured thin films of Au/SnO2 consisting of SnO2 nanostructures decorated with Au nanoparticles were synthesized by thermal evaporation of nanostructured SnO2 thin films combined with deposition of ultrathin Au films by sputtering. The synthesized Au/SnO2 hybrid nanostructured thin films were irradiated with 8 MeV Si3+ ions at room temperature to fluences varying from 2 × 1014 to 5 × 1015 ions/cm2. Effects of MeV ion irradiation on the morphological, structural and optical properties of Au/SnO2 hybrid nanostructured thin films were studied using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman spectroscopy, UV-Visible absorption spectroscopy and photoluminescence spectroscopy (PL). XRD studies revealed the presence of nanostructures of SnO2, Au, Sn and Au-Sn alloy in the as-deposited thin films. XRD and AFM studies showed growth in size of nanostructures in the Au/SnO2 hybrid nanostructured thin films upon ion irradiation. PL studies on as-deposited Au/SnO2 hybrid nanostructured thin film revealed intense peaks at 382, 399, 419, 455 and 542 nm. MeV ion irradiation resulted in strong enhancement in UV emission and visible emissions from SnO2 nanostructures in the Au/SnO2 hybrid nanostructured thin films. Gas sensing studies showed that the sensor prepared using Au/SnO2 hybrid nanostructured thin film exhibits highly enhanced CO gas sensing properties as compared to pure SnO2 nanostructured thin film sensor and shows excellent selectivity for CO gas with negligible interference from CH4, NH3, CO2 and SO2. The mechanism underlying the enhanced gas sensing properties of Au/SnO2 nanostructured thin film is tentatively proposed.