Dispersive relaxation in indium tin oxide contacted silicon oxide memristive devices

Silicon oxide memristive devices exhibit volatile current transients in addition to non-volatile resistive switching. Such transients are candidate temporary states for neuromorphic systems, but their form depends on coupled processes in the oxide and its electrode interfaces. Here, we characterise the transient measured in devices with indium tin oxide (ITO) top contacts using constant-current stress, held-voltage measurements, and X-ray photoelectron spectroscopy (XPS) depth profiling of stressed and pristine samples. The devices first undergo constant-current stress, during which their voltage fluctuates irregularly. Subsequent held-voltage measurements show a fast relaxation without the slow decay branch observed in the Au/Ti-contacted family. The XPS depth profiles show the same core-level positions away from the interface, and differ in the depth progression of the fitted O 1 s components, the stressed sample reaching the metal-oxide to silicon-oxide crossover earlier under the same programmed profiling sequence. With the slow branch absent, we measure and fit the residual relaxation without assigning a microscopic origin. It follows a stretched exponential whose exponent lies below unity over most of the bias range, and both its scale and dispersion vary with applied bias. A volatile device state should therefore be specified by its complete bias-dependent decay under stated measurement conditions, rather than by a single retention time.