4. Conclusion:
Spherical Au nanoparticles on sputtered ZnO films have been fabricated using two-step process. First, ZnO thin films were deposited on inter-digitated alumina substrate by RF magnetron, sputtering at RT, followed by the very thin layer of Au and thermal annealing at 600 oC for 1 h in N2. This yielded the sputtered gold layer on the surface of ZnO to the spherical shapedspherical-shaped gold nanoparticles. All the films exhibited the highly crystalline hexagonal wurtzite ZnO with the analysis of XRD results along (002) axis. The SEM results acknowledged the nucleation of spherical Au nanoparticles, especially in the thermally treated Au/ZnO film in N2. The sensing response of the N2 post-annealed Au/ZnO thin film sensor to 1000 ppm of H2 concentration at 250 oC was increased (80 % to 172 %) TWO times by UV light illumination. Under UV light illumination Au/ZnO thin film sensor exhibited faster response/recovery time and better selectivity compared with pure and air annealed films for the same hydrogen concentration. These results suggest that a combination of post-annealing environment and UV light illumination had a synergetic effect on the gas sensing performance of the sensor. The substantial increase in the response of N2 post-annealed Au/ZnO thin film sensor under UV light irradiation might have been caused by a larger change in the electrical resistance upon the exposure of hydrogen gas molecules due to photo-generated electron–hole pairs. We promise that this study will help the scientific community to realize the high-performance gas sensors using a combination of annealing atmosphere and UV light irradiation.
Acknowledgements:
This work is supported by the NSFC under Grants (No. 61775149) Shenzhen Science and Technology Project (No. JCYJ20160226192754225 No. JCYJ20160307145209361, No. JCYJ20160307111047701), Guangdong Natural Science Foundation (2016A030313059), and Science and Technology plan project of Guangdong (2017A010101018)