Review of hydrothermal ZnO nanowires: Toward FET applications

In this short review, the authors put forward the case that ZnO nanowires grown by low temperature (<100  °C) hydrothermal synthesis routes are suitable for use in both single-wire field effect transistor (FET) devices and multiwire FET devices, and are capable of achieving device characteristics that are at least as good as ZnO nanowires produced by high temperature (>600  °C) vapor phase methods. The hydrothermal synthesis route displays many advantages over vapor phase synthesis routes, the foremost being the compatibility of hydrothermal synthesis with flexible and vulnerable substrates. However, most hydrothermally synthesized ZnO nanowires require annealing at temperatures above 400 °C in order to exhibit field dependent transport necessary for FET devices. Effort should be directed toward understanding the mechanism causing some as-grown hydrothermal ZnO nanowires to display field dependence without the need for annealing. If these mechanisms are understood, great strides can be made in achieving integrated nanodevices using lateral arrays on technologically relevant substrates and understanding the fundamental cause of doping leading to n-type behavior in ZnO.