Ribbed (left) and planar (right) memristor structures
We examined the influence of memristor geometry on switching endurance by comparing ribbed and planar TiO2-based cross-point devices with 50 nm × 50 nm lateral dimensions. We observed that planar devices exhibited a factor of over four improvement in median endurance value over ribbed structures for otherwise identical structures. Our simulations indicated that the corners in the upper wires of the ribbed devices experienced higher current density and more heating during device forming and switching, and hence a shorter life time.
With the Planar structure – the switching layer and the top electrode are made on flat surfaces, resulting in a planar device without kinks. According to the group, the planar devices exhibited a factor of four improvement in the median endurance value over ribbed structures for otherwise identical structures. The researchers attributed the longer lifetime of the planar devices to the lower current density and less heating during device operation.
With the planar structure, the team expects that thicker metal nanowires could be used as electrodes, further reducing the series electrical resistance of the devices and the power consumption of the system. The scientists also anticipate that this new structure will be compatible with standard integrated circuit (IC) industry procedures such as the Damascene process.