Synthesis of flower shaped ZnO thin films for resistive sensing of NO2 gas

A soft chemical synthetic method is used to obtain highly crystalline ZnO flower thin films. Hexagonal wurtzite ZnO structure is observed from X-ray diffraction studies. A large-area jasmine flower-shaped morphology of ZnO is uniformly maintained at all deposition temperatures. The films were characterized by energy dispersive X-ray spectroscopy, Raman spectroscopy and field emission scanning electron microscopy. Elemental analysis showed the presence of Zn and O elements without any other impurity. Raman spectroscopy spectroscopy in combination with elemental and resistivity analysis indicated wurtzite ZnO structure and the presence of oxygen vacancies. The films deposited at 338 K were studied with respect to their gas sensing capability at operating temperatures of 473 K. They show a fast response (65 s) and recovery time (54 s) for NO2 gas at a concentration as low as 10 ppm.