Structures and emission features of high-density ZnO micro/nanostructure grown by an easy hydrothermal method.

Samples of urchin and multipods-like ZnO micro/nanostructure with various morphology, physical, and optical properties are fabricated on glass and silicon substrates through a simple hydrothermal method without any catalyst. The samples demonstrated that high-density ZnO nanorods are assembled to form ZnO micro/nanostructure which has structures that depended on growth time. The influence of growth time and substrate type on the crystalline structure, morphology, and emission response of synthesized ZnO samples were investigated. The samples were characterized by XRD, EDX, FESEM, and PL measurements. A reduction in consumed growth times to produce ZnO micro/nanostructure was achieved. XRD patterns confirmed the wurtzite hexagonal structure of ZnO micro/nanostructure with good crystallinity for (1–4 h) growth time, irrespective of substrate type. Conversely, FESEM images revealed that prolonged growth time of (6–8 h) resulted in destruction of ZnO morphology. EDX patterns showed an oxygen-deficiency- and crystal-defect-mediated growth of ZnO micro/nanostructure on both substrates with different stoichiometric ratios. Optical band-gap energy evaluated from the emission spectra displayed reasonable blue and red shifts depending on growth time (for 1–4 h) and substrate type. The formation mechanism of ZnO micro/nanostructure was demonstrated from the perspective of nucleation and self-assembly of growth unites. [ABSTRACT FROM AUTHOR]