Abstract
ZnO, a well-known direct band-gap II-VI semiconductor with a large exciton binding energy (60 meV), is a promising material for fabricating advanced optoelectronic and electronic devices. Among various nanostructures of ZnO, nanowires (NWs) have attracted particular attention in the past few years due to their unique one-dimensional structures with adjustable length and diameters. Potential applications of these NWs including field emitters, lasers, chemical sensors, solar cells have been extensively investigated recently. Control of ZnO nanowire structures, their distribution, and electrical and optical properties is critical for many applications. Tremendous efforts need to be invested in this research area. In this regard, this article reviews some recent advancement in the controlled growth and doping of ZnO NW arrays by a low temperature electrochemical process. Experimental Conditions such as current/voltage values and seeding layers for ZnO NW growth are first summarized. Then well-organized two-dimensional ZnO NW arrays produced by using PMMA templates and colloidal crystal templates are presented. Finally, electrochemical doping of ZnO NWs with transition metals, noble metals, and nitrogen are reviewed. In each section, structural and electrical or optical properties of the nanowires are briefly discussed. This review showcases the important role of the electrochemical process for the ZnO NW growth under entire property and structure control for future optoelectronic applications. This solution-based process has showed its advantages over other techniques, namely an easy control of growth, doping at low temperatures, low cost, large area deposition, and large scale production.