Reliable RRAM devices utilizing sol-gel derived amorphous Ce2Ti2O7 thin films

Abstract

In this study, amorphous Ce2Ti2O7 (CTO) thin films were prepared on an ITO/glass substrate using the sol-gel method. The effects of film thickness, annealing temperature, post-metal annealing, and the insertion of an additional AlOx layer in between the CTO film and ITO/glass on the resistance-switching characteristics of the device were studied. All samples exhibited bipolar resistive switching (BRS) behavior. The diffusion of Al and self-formed AlOx at the Al/CTO interface were observed in samples under post-metallization annealing (PMA) treatment. The diffused Al atoms can act as dopants to provide additional oxygen vacancies, while the self-formed AlOx prevents the outward diffusion of oxygen ions. A forming-free Al/CTO/ITO sample with a switching cycle of 1565, a Vset/Vreset ratio of −1.1 V/1.0 V, an on/off ratio of ∼102, and a retention time of 104 s can be obtained after a 300 °C PMA treatment. Insertion of an AlOx layer at the CTO/ITO interface can enhance the RS performance of the device. By varying the thickness of the AlOx layer, an optimal combination of RS properties (such as switching cycles of 1926, on/off ratio of ∼103) can be obtained, making it a promising candidate for RRAM applications.