Hydrothermally grown ZnO nanorods in different aspect ratios and their gas sensing properties

On a glass substrate, zinc oxide nanorods (ZnO NRs) arrays of varying aspect ratios have been grown by hydrothermal method at 90 ᴼC with variable ZnO seed layer thicknesses applied by RF sputtering. The structural properties and gas sensitivity of zinc oxide nanorods were studied by using X-ray diffraction (XRD) for analyzing the structural characteristics was discovered that ZnO NRs and seed layer films are both polycrystalline, with the same plane preferred reflection for (002). The seed layer's crystallite size ranges from 19.51 nm to 30.45 nm for thicknesses t1 and t4, respectively. The measurements of the FESEM showed aspect ratios for ZnO NRs ranging from 3.03 for t1 to 4.9 for t4, with growth in different shapes: ZnO NRs for t1, flowers and rod-like shapes for thicknesses t2 and t3, and hexagonal-rod-like shapes for t4. ZnO NRs based on gas sensors and tests of the response of prepared samples on NH3 and CO2 gases showed good sensitivity to both gases at different concentrations (1000, 2000, and 3000 ppm), reaching 65–70 at operating 50 ᴼC.