ABSTRACT
Among many semiconductor nanowires, ZnO with the preferentially hexagonal wurzite-type structure has a wide range of
properties, from metallic to insulating conductivities (including n-and p-type conductivities), a direct wide band gap (∼3.4 eV), large exciton-binding energy (∼60 meV), radiation hardness, high transparency, piezoelectricity, room-temperature ferromagnetism, and chemical-sensing e˜ects (Fan and Lu 2005, Klingshirn 2007, Schmidt-Mende and MacManus-Driscoll 2007). In particular, the advantage of large exciton-binding energy and a variety of nanostructures with relative coste˜ectiveness provides excellent optical and electrical properties as a promising material for blue and ultraviolet optical devices, compared with GaN and GaN-based materials. Moreover, since ZnO has stronger radiation hardness than other common semiconductor materials such as Si, GaAs, CdS, and GaN, ZnO materials are promising for space applications (Look et al. 1999). In recent decades, due to these remarkable properties of ZnO materials and the demand for further miniaturization by semiconductor technology, tremendous e˜orts have been devoted to the growth and characterization of one-dimensional semiconductor ZnO nanostructures (or ZnO nanowires) as well as their versatile applications as a potential material for future nanoelectronics. For example, œeld-e˜ect transistors (FETs) (Goldberger et al. 2005), sensors (Dorfman et al. 2006), light-emitting devices (Bao et al. 2006), solar cells (Law et al. 2005), as well as logic circuits (Park et al. 2005, Yeom et al. 2008) have been extensively investigated and demonstrated.
