Synthesis and Characterization of Micro-Thick TiO2 and HfO2 Memristors

Abstract

Solgel/drop-coated micro-thick TiO2 memristors are investigated and developed for sensing applications. Devices constructed with coated aluminum (Al) electrodes exhibit unipolar I–V characteristics with dynamic turn-on voltage and progressive ROFF/RON ratio loss under applied bias. Endurance failure of micro-thick Al/Al stacks is ascribed to gradual passivation of Al surface resulting from an electrically enhanced oxygen-ion diffusion. By exchanging a single Al contact with higher work-function copper (Cu) metal, two distinct superimposed TiO2 phases are formed. After initial forming, the hybrid stack could achieve a bipolar memristance, with high ROFF/RON (up to 106), and over 10 switching cycles at low operating voltages (±1 V). This chapter also presents micro-thick memristors which are fabricated using alternatively the hafnium-oxide (HfO2) chemistry for the active material. The main focus of the micro-thick HfO2 devices provided here is to investigate the switchability of the novel system and to study the effect of changing key parameters such as (i) the electrode material and (ii) the drying temperature during solgel processing on the resistive switching behavior. The results presented in this chapter highlight important structure to performance findings that provide guidance and insights on optimizing the solgel drop-coating of micro-thick memristor devices.