Resistive switching and impedance characteristics of M/TiO2−x/TiO2/M nano-ionic memristor

• Published in: Solid state ionics 2018-10, Vol.324, p.218-225
• Main Authors: Dash, Chandra Sekhar, Sahoo, Satyajeet, Prabaharan, S.R.S.
• Format: Article
• Language: English
• Subjects: Electrochemical impedance spectroscopy; Memristive switching; Metal oxides; Non-volatile memory; Resistive switching
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2018.07.012

Employing electrochemical impedance spectroscopy (EIS), we demonstrate a novel approach towards characterizing the switching behavior of nano-ionic memristor, M/TiO2−x/TiO2/M where M = Au, fabricated using combined RF/DC magnetron sputtering techniques. The non-linear resistive switching behavior of the device has been investigated using a constant potential sweep technique to observe I-V switching profile (a pinched hysteresis loop) in which ex-situ impedance response has been measured by interrupting the potential sweep (mV s−1) over different distinct regimes (pristine device, SET and after zero-crossing). Accordingly, the obtained EIS spectra are corroborated with oxide circuit model and the corresponding numerical fittings of the impedance response reveals distinct RC frequency domains as exemplified in the equivalent circuit models obtained using the simulated impedance response and attributed to the interfacial barrier between the stoichiometric and non-stoichiometric TiO2 respectively. It is evident that the device shows various functional features as memory element owing to the transport of mobile charges in TiO2−x when the bias potential (V) is applied across the device. It is revealed that EIS studies render a new insight into much acclaimed formation and annihilation of nanofilament like dendrites (magneli phase of titania, TinO2n−1) which are found to be responsible for the change of switching states between low resistance state (LRS) and high resistance state (HRS) respectively. In order to validate the memory retention and endurance characteristics, the reproducible resistive switching is found to occur consistently over 104 s and the device endurance has been verified by toggling between HRS and LRS over 1000 cycles. [Display omitted] •Switching characteristics of M/TiO2-x/TiO2/M memristor are corroborated with ac-impedance spectroscopic interpretation for the first time.•A new insight into much acclaimed filamentary conduction switching mechanism (LRS and HRS) has been affirmed by means of ac Impedance technique.•Reproducible resistive switching (retention time 104s) cycle and the device endurance are proven by toggling between HRS and LRS over 1000 cycles.