During the last several decades, coating technologies have garnered considerable attention, mainly due to their functional advantages over bulk materials, processing flexibility, and cost considerations [157]. Thin film coatings may be deposited using physical methods or chemical methods. The chemical methods can be split according to a gas phase deposition or a liquid phase deposition. These processes are summarized in Figure 4.1, where CVD and Atomic Layer Epitaxy (ALE) are the gas processes.