The experimental ALD process is carried out using the Cambridge NanoTech Savannah S100 system. As shown in Fig. 1, the reactor chamber is customized for up to 100 mm substrates with nearly 150 mm inner diameter and 6 mm in depth. The inert gas, nitrogen, is applied as the precursor carrier and purging gas during the ALD process. The TMA and water vapor are used as the metal-source precursor and oxygen-source precursor respec- tively in this study. The operating temperature of the reactor is maintained at 200 C, while that of the inlet and outlet gas tubes are maintained at 70C and 160C respectively. An Edwards RV5 rotary vane pump is connected to the end of the outlet pipeline to vacuum the reactor before ALD processing, and pump out exces- sive precursor gases during the ALD process.