Morphological, structural and optical properties of ZnO thin solid films formed by nanoleafs or micron/submicron cauliflowers

Thin films of ZnO formed by nano and microstructures with hexagonal crystal phase were successfully synthesized by using pyrolysis technique. At first glance the films resulted divided in 7 zones that were morphologically analyzed and showed the presence of three types of particles: nano-leafs, single microparticles, and particles formed by the addition of microparticles, “clusters”. The largest and therefore the main zone was formed by nanoleafs. Studies on morphology, structure and optical properties of these nanoleafs were obtained and correlated too. The knowledge acquired from these studies allowed the synthesis of nanostructured films entirely formed by nanoleafs with a width of 25 nm and a length 200 nm long regardless of the roughness of the substrate. Energy gap of 3.26 eV was invariant to changes in synthesis parameters. The studies on optical properties of nanoleafs and micro-cauliflower give an energy diagram that account for the location of the energy states introduced by native crystalline defects into the energy band gap and their radiative electronic transitions.