Researchers at the Georgia Institute of Technology have successfully fabricated high- performance field effect transistors using thin films of Carbon 60, also known as fullerene. The new devices - which have electron- mobility values higher than amorphous silicon, low threshold voltages, large on-off ratios, and high operational stability - could have a variety of potential applications including circuitry for displays, active electronic billboards, RFID tags, and other uses that require flexible substrates.
Carbon 60 is attractive for use as an organic semiconductor material because it can provide high electron mobility, which is a measure of how fast current can flow. According to previous reports, Carbon 60 can yield mobility values as high as six square centimeters per volt-second. That benchmark, however, was established using a hot-wall epitaxy process requiring processing temperatures of 250 degrees Celsius, which is too hot for most flexible plastic substrates. Although the transistors produced by Georgia Tech's team display lower mobility - from 2.7 to 5 square centimeters per volt-second - they can be produced at room temperature.
The new transistors were fabricated by depositing Carbon 60 molecules from the vapor phase into a thin film atop a silicon substrate onto which a gate electrode and gate dielectric had already been fabricated. The source and drain electrodes were then deposited on top of the Carbon 60 films through a shadow mask.