Comparative study of TiN and TiN/Ti as bottom electrodes for layered type devices with phase transition VO2 films

DC-sputtered TiN and TiN/Ti conductive layers grown on Si substrates were investigated as bottom electrodes with the aim of realizing phase transition VO2-based layered type devices. The VO2 films prepared at a substrate temperature of 250 °C on both layers were revealed to show more than two orders of magnitude change in resistance in out-of-plane direction. However, the oxidation of TiN layer was found to degrade the out-of-plane semiconductor-metal transition (SMT) of VO2 film in the case of VO2/TiN/Si structure at 400 °C. On the other hand, VO2 film deposited on TiN/Ti/Si substrate at same temperature exhibits an abrupt out-of-plane SMT, in which oxidation of TiN layer was not observed. It was found through the X-ray photoelectron spectroscopy (XPS) depth profiles that the Ti layer played an indispensable role for avoiding oxidation of TiN, due to its high gettering effect for oxygen. Present results show advantage for introducing TiN/Ti layer as bottom electrode with high anti-oxidation ability.