Controlled Growth of Indium Oxide Nanowires for Gas Sensing Application

The In₂O₃ nanowires have attracted enormous attention for gas sensor application due to their advantageous features. However, the controlled synthesis of In₂O₃ nanowires for gas sensors is vital and challenging because the gas sensing performance of the nanowires is strongly dependent on their characteristics.

Here in this patent, we fabricated In₂O₃ nanowires on SiO₂/Si substrate via a simple thermal vapor deposition method with the Au thin film as the catalyst. The growth temperatures were controlled to obtain desired nanowires of small size. The grown In₂O₃ nanowires were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The ethanol gas sensing properties were tested under the dynamic flow of dry air and analytic gas. The synthesized In₂O₃ nanowires have the potential for use in ethanol gas sensor application.

In₂O₃ nanostructures grown at different temperatures ranging from 600 to 900oC have different morphologies. The sample grown at 600oC had a morphology of nanowire, with a diameter of approximately 80 nm and a length of few micrometers. Nanowires grown at 600°C were composed of oxygen (O) and indium (In) elements, with the atomic ratio of [O]/[In] = 3/5. The nanowire was a single phase cubic structure of In₂O₃ crystal. The In₂O₃ nanowire sensor showed typical n-type semiconducting sensing properties. The response decreased from 130 to 75 at 100 ppm when the working temperature decreased from 450°C to 350°C.

The nanowires grown at 600°C by the thermal vapor deposition method had the best morphology with a small diameter of about 80 nm and a length of few micrometers. The In₂O₃ nanowires had a good ability to sense ethanol at varying concentrations in the range of 20 ppm to 100 ppm. The In₂O₃ nanowires can be used as building blocks for future nanoscale gas sensors.