Incorporation of novel ternary Sn-Ga-O and Zn-Ga-O nanostructures into gas sensing devices

Novel ternary nanostructures (ZnO-Ga2O3 nanobrushes, SnO2-Ga2O3 heterostructures and Sn-doped Ga2O3 nanowires) are excellent materials for gas sensing applications due to their large surface areas and structural defects. Also, these nanostructures consist of different materials with different degrees of crystallinity and defect densities thus broadening their gas sensing capabilities. Gas sensing devices, developed in our laboratory based on room temperature capacitance measurements, were first fabricated by standard photolithography and lift-off techniques to pattern platinum (Pt) pads and interdigitated fingers acting as conducting paths. The nanostructures, which were characterized by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and photoluminescence (PL), were then incorporated by the catalyst-assisted growth directly onto the devices. The most efficient devices were those with high yield of nanostructures and with low-resistivity of the Pt pads. To achieve that, different catalysts (nickel, Ni; copper, Cu, and gold, Au) were used for different nanostructures. For example, the best catalyst for the device fabrication of Sn-doped Ga2O3 nanowires was Ni whereas for nanostructures with high Sn content Cu was the best catalyst. Challenges and successes of device fabrication for capacitance-based gas sensing devices are discussed in this work together with some sensing results for such analytes as acetone, acetic acid, isopropanol, dichoropentane, nitrotolouene and nitromethane.