This study was aimed to test the ability of zinc oxide (ZnO) film fabricated by successive ionic layer adsorption and reaction (SILAR) to detect liquid petroleum gas consisting of a mixture of butane/propane gas. The film was fabricated by alternate dipping of pre-cleaned glass substrates in a sodium zincate bath and in a 95°C hot water bath using an automated dipping machine to control the sequence and dipping time. Scanning electron microscopy (SEM) revealed a uniform film consisting of wurtzite ZnO nanorods for the sample grown using 0.1M concentration of sodium zincate and 200 dippings. Current-voltage characterization of the samples showed an average resistivity of 1.343 Ω-m. EDS analysis of the film confirmed the existence of zinc oxide with 65.9% zinc and 34.1% oxygen. The ZnO film exhibited an ability to detect the gas with an average gas response of 0.44, average response time of 14 seconds and average recovery time of 25 seconds using a gas concentration in air of 1.5 % by volume. Response time is the time for the sensor to reach the peak voltage output from the start of gas exposure while recovery time is the time for the voltage output to return to the initial value without gas when the gas is removed from the chamber. The zinc oxide film also showed a voltage output of 100, 109.31, 118.92, 123.61, 133.5, and 149.52 mV when exposed to percent volume gas concentrations of 0, 0.5, 0.75, 1.0, 1.25, and 1.5, respectively with a correlation coefficient of 0.97. The sensor sensitivity is 32 Δ(mV)/Δ(%conc).
Improved zinc oxide film for gas sensor applications