Fig. 1: The effect of cluster-type switching dynamics in analogue linearity.

a Microscopic image of an a-Si synaptic memristor (left inset: scanning electron microscopy (SEM) image of crossbar structure, right inset: illustrated biological synapse). Device schematics with operation mechanism illustration for each memristor situation, b high cation mobility (μ) case for a-Si (pristine) device, c low μ case for a-Si (densified) device, and d low μ and high Ag reduction probability (ΓredAg) case for Ti4.8%:a-Si device. Grey, blue, green, and red spheres represent Ag atoms, Ag ions, Ti atoms, and electrons, respectively. EφAg and EφTi represent standard reduction potentials of Ag and Ti. Analogue conductance updates under three different pulse conditions (blue: 0.6/−0.6 V, green: 0.8/−0.8 V, red: 1/−1 V with 1 μs duration for potentiation/depression) in e a-Si (pristine), f a-Si (densified), g Ti4.8%:a-Si devices. The conductance was measured with a read pulse (0.1 V, 1 μs) after each programming pulse. h Average potentiation and i depression nonlinearity factors of a-Si (pristine), a-Si (densified), and Ti4.8%:a-Si memristors for ten-cycle at each pulse condition.