Περίληψη:
We report on two-step current-induced effects on the electrical,
optical, and structural properties of VO2 films around the
Metal-Insulator Transition (MIT) in synergy with ambient temperature
(T). Simultaneous electrical resistance and transmittance measurements
of VO2 semitransparent thin films as a function of T show that the
electric current modifies the MIT that takes place in two steps: an
abrupt change that increases upon increasing current, implying the
formation of larger metallic domains within the current path,
accompanied by a smoother change that follows the temperature change.
Resistance measurements of thicker bulk-like VO2 films have been also
investigated exhibiting similar two-step behavior. By monitoring the
specimen temperature (T) during resistance measurements, we show that
the abrupt resistance step, accompanied by instantaneous heating/cooling
events, occurs at temperatures lower than TMIT and is attributed to
current-induced Joule heating effects. Moreover, by monitoring To during
current-voltage measurements, the role of T in the formation of two-step
current modified MIT is highlighted. X-ray diffraction with in situ
resistance measurements performed for various currents at room
temperature as a function of To has shown that the current can cause
partially MIT and structural phase transition, leading to an abrupt step
of MIT. The formation of a rutile metallic phase of VO2 under high
applied currents is clearly demonstrated by micro-Raman measurements. By
controlling current in synergy with T below TMIT, the VO2 film can be
driven to a two-step current-induced MIT as gradually a larger part of
the film is transformed into a rutile metallic phase. Published under an
exclusive license by AIP Publishing.
Συγγραφείς:
Manousou, Dimitra K.
Gardelis, Spiros
Calamiotou, Maria and
Likodimos, Vlassis
Syskakis, Emmanuel
