Effects of surface roughness on the electrical characteristics of ZnO nanowire field effect transistors

We have systematically investigated the effects of surface roughness on the electrical characteristics of ZnO nanowire field effect transistors (FETs) before and after passivation by poly (methyl metahacrylate) (PMMA), a polymer-insulating layer. To control the surface morphology of ZnO nanowires, ZnO nanowires were grown by the vapor transport method on two different substrates, namely, an Au-catalyzed sapphire and an Au-catalyzed ZnO film/sapphire. ZnO nanowires grown on the Au-catalyzed sapphire substrate had smooth surfaces, whereas those grown on the Au-catalyzed ZnO film had rough surfaces. Electrical characteristics such as the threshold voltage shift and transconductance before and after passivation were strongly affected by the surface morphology of ZnO nanowires.