Effects of CaO Interlayer on the Performance of Biodegradable Transient MgO-Based Resistive Random Access Memory

Biodegradable transient Mg/MgO/CaO/MgO/ Mg resistive random access memories (RRAMs) with CaO interlayer of different thicknesses have been successfully fabricated on polylactic acid (PLA) substrate at low processing temperature. Comparative analysis shows that the addition of an 8.7-nm CaO interlayer greatly increases the ON/OFF ratio to >10⁵ (by more than ten times) and the retention time of the devices to >10⁴ s. The current-voltage measurements indicate that the low-resistance state (LRS) current is attributed to the Ohmic conduction and the high-resistance state (HRS) current is governed by the Poole-Frenkel (P-F) emission. The CaO interlayer is revealed to elevate the trap energy levels for the P-F emission and work as a block for the mobile charges, thus greatly improving the performance of the memory devices. Moreover, under certain stimulus pulses, the devices can integrate the input pulses, and then 'fire' with output current abruptly increased by several orders, bearing similarities to the integrate-and-fire functionality of neuron. The 'firing' frequencies of devices with the stimulus pulse number are observed to be stochastic, which are able to be modified by the CaO interlayer. Furthermore, immersed in physiological saline the devices dissolve within 1 h except for PLA substrates that are able to completely degrade in proteinase K solution within 15 days.