Resistive Switching Characteristics of Tantalum Oxide with Different Top Electrodes

Abstract

The switching characteristics of tantalum oxide deposited on a platinum (Pt) substrate with tantalum (Ta), titanium (Ti), and copper (Cu) as top electrodes were corroborated. These three top electrodes were chosen because of their different physical and chemical properties. To elucidate the switching phenomenon that occurred in these devices, the switching characteristics of these devices at 25, 60, 80, and 100 degrees C were investigated. At these different temperatures, the current-voltage (I-V) characteristics of all the devices were measured. Ti and Ta, which were reactive top electrodes, were observed to have the same trend in a high-resistance state (HRS) and a low-resistance state (LRS), but for Cu, which was an active top electrode, the current in LRS was observed to have decreased with the temperature increase. This behavior of the Cu top electrode device depicts the formation of a Cu ion metallic filament in the device. An Agilent 4156B revealed the bipolar switching characteristics of all the fabricated devices. SET operation occurred for the positive voltage sweep, which causes the formation of a filament in the oxide layer, and RESET operation deteriorates the filament. The ON/OFF ratios of the devices were dictated by the compliance currents in the SET operation for the Ti and Cu top electrode devices. The different values of the SET and RESET voltages of these devices were due to the different Gibbs free energy for metal oxide formation values, metal work functions, ion migrations, and other physical parameters of these top electrodes. The temperature-dependent study on these devices revealed variations in the HRS and LRS. Based on the observation of the variations in the HRS and LRS with the temperature, the nature of the filament that was being formed and ruptured by the application of a suitable applied stress was suggested. The results of the experiment on the structural data of the fabricated devices were furnished with the energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) measurements.