Improved Performances of Ethanol Sensor Fabricated on Al-Doped ZnO Nanosheet Thin Films

The effect of Al-doped ZnO (AZO) to the sensitivity improvement of ethanol vapor sensor was investigated. The pure ZnO and AZO thin films were synthesized by chemical bath deposition method. Analysis of the crystal structure, chemical composition, and morphology of the samples are carried out using X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). XRD results show that the phase formed is polycrystalline Zn, while the EDS measurements show that the composition of after synthesized AZO were 1.48 at%, 2.90 at%, and 3.55 at%. The SEM results showed flowerlike microstrcuture and nanosheet shaped are formed in the resulting thin films, which are captured by the formation of sheets of transparent structure in AZO. Moreover, the resulting ZnO and AZO sensors were exposed to the different concentration of ethanol vapor as much as 200, 400, and 600 ppm, respectively. The measurement of vapor sensor system performance was tested to analyze the sensitivity and the responsiveness of the AZO thin films. The sensors have highest sensitivity at certain amount of Al doping. It is obtained that the optimum sensitivity of the sensor is investigated at the sample of 2.9 at% Al-ZnO. The sensitivity for pure ZnO sample at concentration of 200, 400, and 600 ppm of ethanol were 70.88%, 78.21%, and 88.57%, respectively. The highest sensitivity for AZO samples is 95.29% at low ethanol concentrations (200 ppm) and 96.68% at the high concentration (parts per million), respectively.