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(a) Current-voltage traces measured during the application of reset voltage ramps. The dashed line corresponds to a linear I(V) with conductance equal to G0 = 2e2/h. (b) Detail of the current-voltage evolution during the last phase of the reset transients. (c) Histogram of conductance at the final reset point; the inset shows the histogram of conductance readings during 100 successive conductance-time traces.
(a) Activation energy of the low-voltage CF current as a function of the CF conductance. The vertical line emphasizes the change of transport regime for CF conductance of the order of G0. (b) Evolution of the CF current during a constant-voltage reset experiment. (c) Control of the transition from the LRS to the intermediate reset state by successive voltage ramps with increasing maximum voltage. From an initial conductance of 125G0, the first six sweeps reduce the CF conductance to 95G0, 70G0, 40G0, 22G0, 13G0, and 8G0, respectively. The seventh sweep disrupts the CF and opens a gap, thus decreasing its conductance by several orders of magnitude, as shown in (d), which depicts the same results in a logarithmic current scale together with a reference line (I = G0V).
Schematic representation of the evolution of the CF structure during the reset transient.
Band structure for crystalline m-HfO2 with O vacancies separated by (a) 4a0, (b) 2 a0, (c) a0 and (d) a0/2. (e) Hopping parameter as a function of vacancy-vacancy separation. (f) Conductance as a function of energy corresponding to a HfO2 matrix where one, two, or three O atom rows are removed. The rows subsequently removed are shown in the instate (marked as “1,” “2,” and “3”), where red and white spheres correspond to O and Hf atoms, respectively.
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