Rate-Limiting Processes Determining the Switching Time in a Ag₂S Atomic Switch

Abstract

The switching time of a Ag 2 S atomic switch, in which formation and annihilation of a Ag atomic bridge is controlled by a solid-electrochemical reaction in a nanogap between two electrodes, is investigated as a function of bias voltage and temperature. Increasing the bias voltage decreases the switching time exponentially, with a greater exponent for the lower range of bias than that for the higher range. Furthermore, the switching time shortens exponentially with raising temperature, following the Arrhenius relation with activation energy values of 0.58 and 1.32 eV for lower and higher bias ranges, respectively. These results indicate that there are two main processes which govern the rate of switching, first, the electrochemical reduction Ag þ þ e -fAg and, second, the diffusion of Ag þ ions. This investigation advances the fundamental understanding of the switching mechanism of the atomic switch, which is essential for its successful device application.SECTION Electron Transport, Optical and Electronic Devices, Hard Matter N anoionics-based resistive switching devices have been attracting much attention in recent years to overcome the physical and economical limitations of current semiconductor technology. 1 A lot of research has been aimed at finding a reliable switching mechanism that can permit ever smaller and more powerful electronics. 2 Recently, we have developed a conceptually new nanodevice called an atomic switch, in which formation and annihilation of a metal atomic bridge across a nanogap between a solid-electrolyte electrode and a counter metal electrode is controlled by a solid-electrochemical reaction. 3 The switching operation can be achieved by only changing the polarity of the bias voltage applied to either electrode. For instance, applying a positive bias voltage to the solid-electrolyte electrode, the metal ions in the electrode reduce to metal atoms, forming a conductive atomic bridge between the electrodes. This decreases the resistance between the two electrodes to a certain ON resistance, which means that the switch is turned ON. When the polarity of the applied voltage is reversed, the metal atoms in the conductive atomic bridge are oxidized and are incorporated back into the solid-electrolyte electrode. This annihilates the conductive bridge between the two electrodes, turning the switch OFF. Similar controlled formation and annihilation of an atomic bridge has also been achieved in an ionic conductive material sandwiched between two electrodes using the solid-electrochemical reaction. 4 The ease of operation and simple structure of the atomic switch make it suitable for configuring logic gates 3 and memory devices. 4 In addition, its unique features, namely, low ON resistance, scalability down to nanometer size, low power consumption, and operation at room temperature, enable the development of a novel programmable logic device 5 that can achieve all functions with a single chip.Because the operating mechanism of the atomic switch is very different from that of conventional semicond...

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