Resistive Memory and Memristor
A Memristor is a two terminal device with behavior similar to that of an ohmic resistor but with variable resistance. In its simplest form, the Memristor consists of a dielectric material sandwiched in between two metal electrodes. The current research on Memristors aims towards the development for application in fast and non-volatile memory devices, as well as in reconfigurable and neuromimetic nano-circuits. Indeed, it combines all aspects of the NaMLab strategy - the development of energy efficient and re-configurable devices based on dielectric materials.
The central aim of our research is the development of resistive memories – the so called RRAM, which is believed to be one of the possible candidates for the realization of the universal memory, characterized by very fast access times, non-volatility, and very low power consumption. In this context, the digital switching behavior, endurance, retention and reliability is of utmost relevance. A further interest is the application of Memristor devices in neuromimetic circuits, exhibiting the united functionality of logic and memory in one device. Main focus is the analog switching behavior between several resistive states for elements in a dense arrangement.
Main part of our activities is so far the deposition of dielectric thin films, the physical and electrical characterization as well as the tuning of the resistive switching properties. Different dielectric materials (i.e. TiO2 and Nb2O5) are explored. In Fig. 1 the schematic of a typical material stack is illustrated. Another central building block is the design of metal-insulator-metal (MIM) test structures on micro- and nanometer scale. Fig. 2 shows the SEM image of our cross-point MIM test structures, allowing for characterization of real passive arrays. A further important part of our activities is the development of electrical characterization techniques for the different devices. C-V, I-V and pulsed measurements are used to analyze electrical characteristics. In Fig. 3 the switching behavior of Nb2O5 is shown. After the typically required initial electroforming process bipolar switching was successfully demonstrated for both, amorphous and crystalline phase. Our results motivate further research into Nb2O5 phase optimization for memory devices.
Further research will be also include the modification of resistive switching layers by ion implantation in close cooperation with the Helmholtz-Center Dresden-Rossendorf (HZDR).
Cooperation: HZDR, Technische Universität Dresden, FZ Jülich
Contact: Dr. Stefan Slesazeck
