Non-Polar and Complementary Resistive Switching Characteristics in Graphene Oxide devices with Gold Nanoparticles: Diverse Approach for Device Fabrication.

Downscaling limitations and limited write/erase cycles in conventional charge-storage based non-volatile memories stimulate the development of emerging memory devices having enhanced performance. Resistive random-access memory (RRAM) devices are recognized as the next-generation memory devices for employment in artificial intelligence and neuromorphic computing, due to their smallest cell size, high write/erase speed and endurance. Unipolar and bipolar resistive switching characteristics in graphene oxide (GO) have been extensively studied in recent years, whereas the study of non-polar and complementary switching is scarce. Here we fabricated GO-based RRAM devices with gold nanoparticles (Au Nps). Diverse types of switching behavior are observed by changing the processing methods and device geometry. Tri-layer GO-based devices illustrated non-polar resistive switching, which is a combination of unipolar and bipolar switching. Five-layer GO-based devices depicted complementary resistive switching having the lowest current values ~12 µA; and this structure is capable of resolving the sneak path issue. Both devices show good retention and endurance performance. Au Nps in tri-layer devices assisted the conducting path, whereas in five-layer devices, Au Nps layer worked as common electrodes between co-joined cells. These GO-based devices with Au Nps comprising different configuration are vital for practical applications of emerging non-volatile resistive memories.

Enhanced resistive switching in forming-free graphene oxide films embedded with gold nanoparticles deposited by electrophoresis.

Forming-free resistive random access memory (ReRAM) devices having low switching voltages are a prerequisite for their commercial applications. In this study, the forming-free resistive switching characteristics of graphene oxide (GO) films embedded with gold nanoparticles (Au Nps), having an enhanced on/off ratio at very low switching voltages, were investigated for non-volatile memories. The GOAu films were deposited by the electrophoresis method and as-grown films were found to be in the low resistance state; therefore no forming voltage was required to activate the devices for switching. The devices having an enlarged on/off ratio window of ∼10(6) between two resistance states at low voltages (<1 V) for repetitive dc voltage sweeps showed excellent properties of endurance and retention. In these films Au Nps were uniformly dispersed over a large area that provided charge traps, which resulted in improved switching characteristics. Capacitance was also found to increase by a factor of ∼10, when comparing high and low resistance states in GOAu and pristine GO devices. Charge trapping and de-trapping by Au Nps was the mechanism responsible for the improved switching characteristics in the films.

Temperature tuned defect induced magnetism in reduced graphene oxide.

The existence of ferromagnetism in the wonder material graphene has opened up the path for many future spintronics and memory applications. But simultaneously it is very important to understand the variation of these properties with temperature in regards to the device applications. Here we observed defect induced ferromagnetism in chemically reduced graphene and the effect of temperature on it. Several theoretical studies have proved that the main cause of ferromagnetism in graphene is due to various defects. The observed results established that these defects can be mended by treating the samples at elevated temperatures but sacrificing the ferromagnetism simultaneously. Hence, temperature plays a crucial role in controlling the magnetism as well as the defects in graphene. In this study we revealed that at 600 °C the self-repair mechanism helps the defects to mend but resulting in the decrement of magnetization and providing a good quality graphene with less defects.