Abstract
Memory devices based on resistive switching (RS) have not been fully realised due to lack of understanding of the underlying switching mechanisms. Nature of ion transport responsible for switching and growth of conducting filament in transition metal oxide based RS devices is still in debate. Here, we investigated the mechanism in Niobium oxide based RS devices, which shows unipolar switching with high ON/OFF ratio, good endurance cycles and high retention times. We controlled the boundary conditions between low-conductance insulating and a high-conductance metallic state where conducting filament (CF) can form atomic point contact and exhibit quantized conductance behaviour. Based on the statistics generated from quantized steps data, we demonstrated that the CF is growing atom by atom with the applied voltage sweeps. We also observed stable quantized states, which can be utilized in multistate switching.
Highlights
To explore the mechanism of growth of the CF, we investigated Pt/Nb2O5/Al devices, which showed unipolar switching with high ON/OFF ratio, good endurance cycles and high retention times
The Niobium oxide thin films (30 nm) were deposited using reactive magnetron sputtering from metallic Nb target using a dc power in an atmosphere of 94% Ar and 6% O2 at room temperature
The electrical dc measurement of the devices was performed at room temperature using two probe system equipped with Agilent B2901A source-meter
Summary
The conventional silicon-based ‘flash’ memory has reached its limitation due to its slow programming speed, poor endurance and relatively high operating voltage.[1,2] As an alternative, memristive systems have attracted extensive research interest due to their potential usage as components for non-volatile memory[2,3] as well as for logic[4,5] and, brain-inspired neuromorphic computing.[6,7,8] These two-terminal devices have advantages due to their scalability down to atomic level, high-density storage, low-power consumption, and high-speed features.[6,9,10,11] The memristive devices show insulating properties on macroscopic scale, but reversibly switch into ionic-electronic conductor at nanoscale dimensions due to formation/dissolution of localized conducting filaments. To explore the mechanism of growth of the CF, we investigated Pt/Nb2O5/Al devices, which showed unipolar switching with high ON/OFF ratio, good endurance cycles and high retention times. We controlled the growth of the CF in the devices to form atomic point contact and observed quantization of conductance with integer (n) and half-integer (n+1/2) multiples of quantum of conductance (G0 = 2e2/h ∼77.4 μS) states during current vs voltage (I-V ) measurements.
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