“…pulsed laser deposition [1], magnetron sputtering [2,3], electron beam evaporation [4,5], etc., and performances of cerium oxides films were widely examined [4,[6][7][8][9][10][11]. Interfacial reactions between CeO 2 films and substrates are also concerned during post-deposition annealing treatment [2,6,12,13], and intermediate sub-oxide layers are observed by TEM [3], XPS [4,6,12,14], AES depth profile [4] etc. When annealed in ultra-high vacuum (UHV) condition, CeO 2 thin films are identified to be reduced to Ce suboxide at a certain temperature [12,[14][15][16], and to be oxidized to CeO 2 readily under the condition of O 2 exposure [15].…”