Highly conductive and transparent films have many important applications such as transparent electrodes for optoelectronic devices and transparent heat mirrors for solar energy utilization. Although indium-tin-oxide (ITO) thin films are generally used for practical applications, ITO is a relatively expensive material because indium is not abundant. Recently Al-doped ZnO thin films have attracted interest as a transparent and conductive coating material because the low cost of this material makes it attractive for large-scale applications. In this book, the optimized deposition conditions for the preparation of Al-doped ZnO thin films by reactive DC magnetron sputtering method will be discussed. The structural, surface morphological, electrical, and optical properties of Al-doped ZnO thin films were reported systematically.