Highly Uniform Resistive Switching In Hfo2 Films Embedded With Ordered Metal Nanoisland Arrays

Memristors enter a critical developmental stage where emerging large-scale integration methods face major challenges with severe switching instabilities in the oxide layer. Here, the superior uniformity is achieved within HfO2 films by embedding highly ordered metal nanoisland (NI) arrays. Embedded films exhibit a significant reduction in both SET and RESET while displaying enhanced uniformity in operating voltages and resistance states. This behavior is attributed to the concentration of electric fields along Pt and Ti NIs and their interactions with the surrounding oxide film matrix environment, which induce separate and distinct filamentary formation mechanisms that affect the stability. A method is reported to further optimize the uniformity of the SET voltage by translating the NI array position down the film-thickness dimension towards the bottom electrode. A comparison of the density and distribution of the oxygen vacancies responsible for the formation/dissolution of conducting filaments is made via combined electrostatic force microscopy and conductive atomic force microscopy (c-AFM) studies. Finally, complete observation of the morphological evolution of conducting filaments produced by Pt and Ti is enabled by 3D c-AFM nanotomography and cross-sectional scanning transmission electron microscopy-energy dispersive spectroscopy to provide direct correlations between NI-oxide interactions and overall switching performance.