Electrical oscillations induced by the metal-insulator transition in VO2

Abstract

We systematically investigate the characteristics of an electrical oscillation observed in two-terminal vanadium dioxide ͑VO 2 ͒ devices. These oscillations are observed at room temperature in a simple electrical circuit without inductive components. The circuit is composed only of a dc voltage source, the VO 2 device, and a standard resistor connected in series with the device. We explain why the observed oscillations are a result of the percolative metal-to-insulator transition ͑MIT͒ of VO 2 and the coexistence of the metal and insulating phases. Specifically, oscillations are attributed to the construction and destruction of capacitive regions composed of regions of the semiconducting phase, ͑as dielectric material͒ and metallic phase electron carriers, induced by the MIT ͑as capacitor electrodes͒. Since the coexistence of these phases-and thus the capacitive regions-is destroyed by elevated temperature, the MIT oscillation is not explained in terms of significant heat input but rather in terms of a voltage-triggered effect. It is also discussed whether the current jump at the onset of the oscillations is driven by Mott physics or by Peierls physics relying on a structural phase transition. Furthermore, the electrical parameter space surrounding these oscillations is explored, and a generation window is identified. Within this generation window, the oscillation frequency can be continuously tuned by adjusting applied voltage or by an external circuit component, such as resistor or added capacitor. The frequency of oscillations can be increased up to Ͼ1 MHz.

Hybrid Si-VO_2-Au optical modulator based on near-field plasmonic coupling

“…It is therefore likely that more careful study will yield similar results for electrical excitation. In particular, evidence for possible increased speed of transition for smaller VO 2 patch size [47] is consistent with a conjectured two-stage quasielectric-field excitation [48]. If it is possible to metallize the VO 2 without transforming the crystal structure, then electrical switching speeds substantially faster than 1 ns should be possible.…”

Electro-optical phase-change 2 × 2 switching using three- and four-waveguide directional couplers

“…An invention in the present work is arranging different active lengths for state 2 (L cr ≦L am ) to provide adjustment of the optical retardation ΔβL offered by the PCM in state 2. Here, we focus on the well-known PCM Ge 2 Sb 2 Te 5 known as GST [4,5], which is reported to have electro-optical properties superior to those of the aforementioned vanadium dioxide [2,6]. Other than GST, several alternative PCMs also can be applied in the implementations in this paper [7][8][9].…”

Current-Controlled Optical Modulation in Thin VO2 Wires

“…The differences in the current at the onset of transition and the width of the hysteresis loop between the two transitions strongly suggest that the two transitions are different in nature. Since the second transition occurs at a much higher current than the first transition, we believe the first transition was electronically induced, while the second has a thermal character [3] .…”