Single step hydrothermal approach for devising hierarchical Ag–ZnO heterostructures with significant enhancement in field emission performance

Abstract

Hierarchical Ag–ZnO heterostructures have been synthesized via a template free single step hydrothermal method. Structural and morphological studies reveal the formation of heterostructures comprised of Ag nanoparticles (∼20 nm) organized on tapered ZnO nanorods under the prevailing experimental conditions. A plausible reaction and growth mechanism has been discussed. Furthermore, the hierarchical creation of ZnO with Ag as a relatively low work function material offers an effective approach to tailor its field emission properties. The field emission studies reveal a remarkable low turn-on field of ∼ 1 V μm⁻¹, corresponding to an emission current density of ∼10 μA cm⁻², and an emission current density of ∼400 μA cm⁻² has been drawn at an applied field of 2.24 V μm⁻¹. In addition, the Ag–ZnO heterostructures exhibit a good emission current stability at the pre-set value of ∼1 and 4 μA over a duration of 3 h. The enhancement of the field emission characteristics resulting from Ag nanoparticles decorating the tapered ZnO nanorods is discussed on the basis of band structure modifications. The ease of the synthesis route and the remarkable field emission properties offer Ag–ZnO heterostructures as a promising electron source for high current density applications.