Abrupt Metal-insulator Transition Research Articles

Switching of the Mott transition based on hole-driven MIT theory

Switching voltage of first-order metal–insulator transition (MIT) in VO 2, an inhomogeneous strongly correlated system, is changed by irradiating an infrared light with λ=1.5 μm and applying the electric field (photo-induced switching). This was predicted in the hole-driven MIT theory in which hole doping of a low concentration below 0.01% into conduction band (Fermi surface) induces the abrupt MIT as correlation effect. The switching is explained by the Mott transition not the Peierls transition.

Observation of abrupt first-order metal–insulator transition in Be-doped GaAs

An abrupt first-order metal–insulator transition (MIT) as a current jump is observed in Be-doped GaAs by inducing holes in a very low concentration of n p ≈ 5 × 10 14 cm - 3 into the valence band by the electric field; this is anomalous. In a higher hole-doping concentration of n p ≈ 6 × 10 16 cm - 3 , the abrupt MIT is not observed at room temperature, but measured at a low temperature. The upper limit of the temperature allowing the MIT is deduced from experimental data to be approximately 440 K. The abrupt MIT is intrinsic and is compared with “breakdown” (an unsolved problem) produced by a high electric field in semiconductor devices.

Interface effect on metal-insulator transition of strained vanadium dioxide ultrathin films

The interface effects on the metal-insulator transition (MIT) of strained VO2 ultrathin films grown epitaxially on TiO2 (001) single crystal substrate were investigated. Varying the surface conditions of TiO2 substrate, such as the roughness and the surface reconstructions, produced the remarkable changes in the MIT events of VO2 thin films, including the transition temperature and the abruptness. The presence of the surface reconstructions was found to be detrimental for applying effectively strain effects due to the strain relaxation in the c axis of VO2 thin films. The abrupt MIT in strained VO2 thin films, deposited on the substrate without such detrimental surface reconstructions, was successfully maintained down to around 5nm film thickness.

Abrupt metal–insulator transition observed in VO 2 thin films induced by a switching voltage pulse

An abrupt metal–insulator transition (MIT) was observed in VO 2 thin films during the application of a switching voltage pulse to two-terminal devices. Any switching pulse over a threshold voltage for the MIT of 7.1 V enabled the device material to transform efficiently from an insulator to a metal. The characteristics of the transformation were analyzed by considering both the delay time and rise time of the measured current response. The extrapolated switching time of the MIT decreased down to 9 ns as the external load resistance decreased to zero. Observation of the intrinsic switching time of the MIT in the correlated oxide films is impossible because of the inhomogeneity of the metallic and the insulating states. This indicates that the intrinsic switching time is in the order of less than a nanosecond.