(Cu ! Cu
z+ + ze
À
, where z is either 1 or 2) occurs at the Cu/Ta 2 O 5 interface, and
then positively charged Cu
z+ ions in Ta 2 O 5 migrate toward the Pt negative electrode.
The concentration of Cu
z+ ions near the Ta 2 O 5 /Pt interface gradually increases and
reaches supersaturation, resulting in heterogeneous Cu nucleation on the Pt electrode. Subsequently, as the Cu nucleus continues to grow by continuous voltage
application, the bridge of Cu filaments is formed between the Cu electrode and the Pt
electrode, and the element shows the switching from the OFF state to the ON state.
Subsequently, when a negative voltage is swept to the Cu electrode, high density
current flows in the formed Cu nanofilament due to the low resistivity and Joule heat
Fig. 12 (a, b) Typical forming behaviors (1st sweep) and subsequent switching behaviors (10th
sweep) for gap-less type atomic switches with element structures of Cu/Ta 2 O 5 /Pt and Ag/Ta 2 O 5 /Pt,
respectively. (c, d) The SET and RESET mechanisms of the Cu/Ta 2 O 5 /Pt cell under application of
positive and negative bias to the Cu electrode, respectively [16]
Invention and Development of the Atomic Switch
13
z+ + ze
À
, where z is either 1 or 2) occurs at the Cu/Ta 2 O 5 interface, and
then positively charged Cu
z+ ions in Ta 2 O 5 migrate toward the Pt negative electrode.
The concentration of Cu
z+ ions near the Ta 2 O 5 /Pt interface gradually increases and
reaches supersaturation, resulting in heterogeneous Cu nucleation on the Pt electrode. Subsequently, as the Cu nucleus continues to grow by continuous voltage
application, the bridge of Cu filaments is formed between the Cu electrode and the Pt
electrode, and the element shows the switching from the OFF state to the ON state.
Subsequently, when a negative voltage is swept to the Cu electrode, high density
current flows in the formed Cu nanofilament due to the low resistivity and Joule heat
Fig. 12 (a, b) Typical forming behaviors (1st sweep) and subsequent switching behaviors (10th
sweep) for gap-less type atomic switches with element structures of Cu/Ta 2 O 5 /Pt and Ag/Ta 2 O 5 /Pt,
respectively. (c, d) The SET and RESET mechanisms of the Cu/Ta 2 O 5 /Pt cell under application of
positive and negative bias to the Cu electrode, respectively [16]
Invention and Development of the Atomic Switch
13