Insulator-Metal Transition In Thermal Imagers

What causes vanadium dioxide films to conduct electricity has been discovered by researchers (insulator-metal transition). Their discoveries will enable thermal imaging devices with higher sensitivity and reaction rates than currently available analogs.

While 100-nanometer thin vanadium dioxide (VO2) films do not normally conduct electricity, their resistance drops to 100,000 times when slightly heated. It could happen when a voltage is applied. This property allows for developing high-speed switchable devices and sensors for direct current or alternating signals in the terahertz, microwave, optical, or infrared ranges.

In the mid-twentieth century, materials scientists discovered that VO2 films could become conductive. The precise mechanism underlying the change in the material’s electrical properties was unknown until now. Knowing about that mechanism (insulator-metal transition) allows for more application-oriented material design. It includes creating thin films with specific properties, such as the temperature at which conductivity changes or the resistance ratio before and after heating.

Sensors for uncooled bolometers are one of the most useful applications for these films. Thermal imaging systems rely on bolometers. VO2 films can improve sensitivity and reaction time, allowing them to be used on fast-moving objects.

The researchers proposed a VO2 film transition scenario between the insulating and conductive states. First, the film heats up, and conductive areas appear sporadically.

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