Comprehensive study of hydrothermally grown ZnO nanowires

A hydrothermal procedure has been implemented to grow single-crystal ZnO nanowires (NWs) on sol-gel deposited seed layers. The main characteristics (diameter, length, and aspect ratio) of derived NWs have been studied by scanning electron microscopy in relation to morphological and structural properties of the ZnO films (mean grain size, surface coverage rate, and texture coefficient) and growth process parameters (growth duration and multi-growth procedure). It is shown how suitable combinations arising from the influence of the seed layer properties, growths of various durations, and implementation of a multi-growth process enable to finely tune the NW characteristics in a large range of values, i.e., a diameter, length, and aspect ratio varying in the 30-225 nm, 1.0-9.0 A mu m, and 30-50 ranges, respectively. On the basis of investigated experimental conditions, a simple model is developed that suitably describes the NW crystal growth as a function of the seed layer properties and growth duration. According to this model, lateral and longitudinal growth rates of around 0.01 nm/min and 25-30 nm/min, respectively, are extracted from experimental data and a minimal NW diameter of around 20 nm is predicted.