Studies of structural evolution and sensing properties of ZnO nanocrystalline films

ZnO nanocrystalline films have been prepared on Si(1 0 0) substrate using direct current (D.C) magnetron sputtering technique at room temperature. The thickness of nanocrystalline films almost linearly increased with deposition duration and the sizes of crystalline grains almost kept unchanged. After deposition, thermal annealing was performed at 800 °C in atmosphere for 2 h in order to improve the qualities of ZnO thin films. Scanning electron microscope (SEM) images showed the surface roughness of the films less than 45 nm. X-ray diffraction (XRD) patterns revealed the slight evolution of the crystal structures. Raman scattering spectra confirmed the data obtained from X-ray diffraction measurements.With these ZnO nanocrystalline films, prototypic gas sensors were fabricated. Both sensitivity and response of the sensors to different gases (H2 and CH4) were investigated. A quick response of time, less than 1 second to CH4 gas sensor has been achieved.

Research highlights▶ The average grain sizes of thin films remains nearly unchanged with deposition time when is prepared by D.C magnetron sputtering technology; ▶ Structural evolution can be observed due to the structure disorder with an increase of film thickness; ▶ The response time and recover time to methane of the ZnO-based gas sensor are less than 1 s and 10 s.