Decay emission study of ZnO nanostructures obtained by low-pressure vapor transport technique

Abstract

Currently, the search for inexpensive, non-toxic, and environmentally friendly materials for optoelectronic applications has led to an increased interest in one-dimensional ZnO materials. Attributes such as their high surface area, crystalline phase purity, and high photoexcited response make them attractive for light emission, biosensing, and energy harvesting applications. However, there is still a need for studies that correlate the optical and structural properties of these materials, so they can be integrated as functional building blocks in practical devices. In this work, we report the growth of 1D ZnO nanostructured films using a low-pressure vapor transport technique. Gold-plated substrates allowed us to achieve different types of homogeneous films composed of nanowires/nanorods. Through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-Ray diffraction (XRD) the high-crystalline structure and morphological properties of the materials were determined. The presented methodology also offers control over the growth direction of the nanostructures, as both random and highly aligned matrixes were obtained. Finally, the optical properties of the system were studied by photoluminescence spectroscopy (PL). Along with the excitonic emission, a significant role of defect-related luminescence was found, allowing us to interpret the emission mechanism for the different morphologies of ZnO nanostructures. Time-resolved PL experiments determined decays between 1.9-0.3 ns where an enhancement in the carrier's lifetime was observed as the size of the nanostructure increased. The present study could help us to design efficient ZnO nanostructures with control over their morphology and controllable optoelectronic properties for modern device fabrication.