The role of graphitic filaments in resistive switching behaviour of amorphous silicon carbide thin films

Resistive switching in amorphous silicon carbide (a-SiC) films deposited by a single composite target magnetron sputtering process is reported. Switching performance as a function of thickness of the films (50, 100 and 300 nm) as well as different top metal electrodes (Cu, Pt and Ag) with the bottom electrode fixed as Au, is investigated. The switching parameters (Forming Voltage, Set and Reset voltages and corresponding currents) are found to be dependent on thickness of SiC films and it is observed that 100 nm is the optimal thickness for best endurance. The interface between metal electrode and a-SiC films plays a more significant role in achieving switching performance. Resistance Off/On ratios of 108, retention times >104 s and endurance of 50 cycles are achieved in the best devices. Cross-sectional scanning electron microscopy provides evidence that the mechanism of switching involves the formation of carbonaceous filaments and Raman spectroscopy indicates that these filaments are nanocrystalline graphite in nature. The current work clearly establishes that there is dissociation of SiC during the switching cycles leading to formation of nanocrystalline graphitic filaments. These contribute to switching, in addition to the metallic filaments, in the a-SiC based resistive memory device.