1D nanomaterials are also expected to play an important role as both interconnects and functional units in fabricating electronic, optoelectronic, electrochemical, and electromechanical devices with nanoscale dimensions [5]. Among the inorganic semiconductor nanomaterials, 1D metal oxide nanostructures are the focus of current research efforts in nanotechnology since they are the most common minerals on the Earth due to their special shapes, compositions, and chemical, and physical properties. They have now been widely used in many areas, such as transparent electronics, piezoelectric transducers, ceramics, catalysis, sensors, electro-optical and electro-chromic devices [6�C8].

Doubtlessly, a thorough understanding of the fundamental properties of a 1D metal oxide system is prerequisite in research and development towards practical applications.

Table 1 shows the fundamental physical properties of some important metal-oxide semiconductors, including zinc oxide (ZnO), tin dioxide (SnO2), copper oxide (Cu2O), Gallium oxide (��-Ga2O3), Hematite (��-Fe2O3), Indium oxide (In2O3), Cadmium oxide (CdO) and Ceria (CeO2).Table 1.Fundamental physical properties of some important metal-oxide semiconductors.Among all nanoscale devices, the photodetectors are critical for applications as binary switches in imaging techniques and light-wave communications, as well as in future memory storage and optoelectronic circuits [10,11].

With large surface-to-volume ratios and Debye length comparable to their small size, these 1D nanostructures have already displayed superior sensitivity to light in experimental devices.

Until now, various 1D metal-oxide nanostructures have been used for the fabrication of photodetectors, and the related mechanism has been investigated over the years. This Brefeldin_A mechanism is outlined below, using ZnO nanowire (NW) as a model system. Essentially, all experiments carried out to date on metal-oxide Cilengitide nanostructures indicated that the role of oxygen vacancies is predominant for the electronic properties, similar to the bulk systems [8].As discussed by Yang et al, Wang et al and other groups [9,12�C14], in the dark, the oxygen molecules absorb on the ZnO NW surface and capture the free electrons present in a n-type oxide semiconductor [O2 (g)+e?��O2? (ad)], and a low-conductivity depletion layer is formed near the surface (Figure 1b), that results in the reduction of the channel conduction.