Figure 2

SEM images of the ZnO structures grown on the sensor board: (a) and (b) without seeding layer (5000x and 25000x, respectively); (c) and (d) 03GO03ZnAc (5000x and 25000x, respectively); (e) and (f) 06GO06ZnAc (5000x and 25000x, respectively); (g) and (h) 12GO12ZnAc (5000x and 25000x, respectively). (i) Raman spectra.