The Resistive Switching Characteristics of TiN/HfO2/Ag RRAM Devices with Bidirectional Current Compliance

Abstract

The performance of TiN/HfO2/Ag resistive random-access memory (RRAM) devices combining the oxygen-based RRAM (OxRRAM) and conducting bridge random-access memory (CBRAM) was studied. Current compliance (CC) values could significantly affect the resistive switching process: with unidirectional CC, permanent breakdown for the devices was observed. With bidirectional smaller CC, the stable bipolar resistive switching mode was obtained, and the cation injection played a leading role in the resistive switching process, while the devices with higher CC always remained in low-resistance state (LRS). The resistance–voltage (R–V) curve and conducting mechanism were analyzed for the bidirectional smaller CC devices, indicating ohmic conduction for the LRS, while the space charge limited the current for the high-resistance state. The results of x-ray photoelectron spectroscopy showed that oxygen vacancies participated in the resistive switching process. It could be concluded that conducting paths were formed from conducting filaments of oxygen vacancies and conducting bridges of Ag grains, and the different formation rate of conducting filaments related to the values of CC was the prime reason for the various changes. Moreover, the characteristics of TiN/HfO2/Ta devices proved the universality of bidirectional CC. The method of making the OxRRAM and CBRAM coexist in the RRAM devices may offer a way to fabricate devices with low power consumption.