Optoelectronic and all-optical multiple memory states in vanadium dioxide

Abstract

Vanadium dioxide exhibits a well-known insulator-to-metal transition during which several of its physical properties change significantly. A hysteresis loop develops for each of them as the material is heated and then cooled through the transition. In this work VO 2 / SiO 2 samples were maintainedby heat sinking-at a selected temperature within the heating branch of the hysteresis loops for resistance and near-infrared transmittance, while brief thermal excursions of the VO 2 film were caused by either voltage pulses applied to the film or laser light pulses irradiating the film. These pulses had durations from milliseconds to a few seconds and the resulting drops in resistance or transmittance were easily and repeatably measurable without appreciably affecting their new values. A sequence of equal-duration pulses ͑for either equal-voltage or equal-irradiation pulses͒ caused the resistance and infrared transmittance to continue to drop, each time by a smaller amount, and larger energy pulses were required in order to cause drops comparable with the initial one. The ability of the film to change the values of the measurands in this manner with additional pulses was maintained up to a limit defined by the outer hysteresis curve for the measurand in question. The results presented show that a plurality of memory "states" in VO 2 can be established or "written" either by voltage pulses or by light pulses applied to the material, and queried or "read" by resistance or transmittance readings, or both. These states were found to remain stable for at least several hours, as long as temperature was kept constant, and are expected to persist indefinitely under this condition. In the all-optical case, if the same light beam is used for writing and reading the memory state, the device is an optical analog of a memristor.

The Memristive Properties of a Single VO2 Nanowire with Switching Controlled by Self‐Heating

“…In previous results, the specifi c temperature, which can maintain the switched resistance, was determined between the two transition temperatures in heating and cooling cycle of the hysteresis in the R-T curve because the resistance can be changed only in the hysteresis loop. [12][13][14] Likewise, since the temperature of the nanowire can be controlled by self-Joule heating through the application of specifi c bias voltage, [ 35 ] to fi nd out the amount of the specifi c bias voltage, we investigated the resistance change of the those previously reported, [30][31][32] devices based on a single VO 2 nanowire can have the advantage of low power consumption.…”

“…However, although the switched resistance can be maintained well near the T c , it can provide only a small range of accessible resistance of less than two orders of magnitude at fi xed temperature because only a part of the hysteresis is used. [12][13][14] Furthermore, using additional heating source for maintaining the resistance can make it diffi cult to achieve low power consumption and high-density integration. Thus, it is necessary to develop innovative strategy towards achieving a lowpower, high-density, and two-terminal memristor for practical application in non-volatile memory device.…”

“…[20][21][22][23][24][25][26] Over the years, memristors based on thin-fi lm VO 2 have been demonstrated as the memory device with switchable and retainable resistances. The change of resistance was obtained by providing pulse-type energy sources, such as voltage, light, and current, [12][13][14] that played the part of a trigger for MIT. The resistance could be retained by keeping the temperature near the transition temperature ( T c ) of about 68 °C using an additional heating source.…”

Optically-Triggered Nanoscale Memory Effect in a Hybrid Plasmonic-Phase Changing Nanostructure

“…This dynamic is highly repeatable, lasts for several hours and persists as long as the external stimulus is not varied. [34][35] Hence the entire phase-space of this PCM can be optically addressed when the hybrid nanomaterial is latched at different starting temperatures during the IMT.…”

Hot electron injection driven phase transitions

“…12 The SMT in VO 2 is manifested by large changes in resistivity and dielectric functions 4,[13][14][15] that are accompanied by a simultaneous structural change [16][17][18][19] from the low-temperature monoclinic insulating phase with band gap of ∼0.7 eV 20 to the high-temperature rutile metallic phase. It is generally agreed that the SMT arises from a combination of Peierls and Mott mechanisms.…”