(color online) Curves of (a) i–v, (b) v–t and i–t, (c) r–v, (d) r–t and x–t of the improved model. Parameters are μ_v = 1 × 10⁻¹⁴ m/V², D = 10 nm, R_on = 100 Ω, R_off = 16 k Ω, vt = 0.01 V, ε₀ = x₀ = 0.5, ω = 2, σ = 0.1, α = 0.01, j = p = 1.