With a reduction in size, unique electrical, mechanical, chemical and optical properties have been reported in semiconductor nanowires, offering an unprecedented broad range of applications. These applications encompass various disciplines of science and engineering such as electronics, photonics, biomedical sensors and communications. For instance, nanowire diameters are comparable to the sizes of many biological and chemical species. Specific receptor proteins can be linked to the nanowire active surface. The binding of charged biological/chemical molecules to this receptor-modified-surface changes the properties of the nanowire surface, which can then be measured. In addition, nanowires have a very large surface area to volume ratio. Therefore, nanowires can be used as ultra-sensitive sensors, which can sense chemicals, pH, DNA, drugs, and even viruses with single molecule detection sensitivity.