Research

With the spread of IoT, the amount of information that needs to be collected and stored continues to increase as not only personal computers but also various devices are connected to the internet. Current information storage devices use only electrical resistance changes in semiconductors, but with this research, we have developed a device that can use color changes in addition to electrical resistance changes for information display and storage. A three-terminal all-solid-state thin-film transistor structure was produced on a glass or plastic substrate with source, drain, and gate electrodes consisting of a laminate of an amorphous WO3 thin film (100 nm thick)/nanoporous glass thin film (300 nm)/polycrystalline NiO thin film (50 nm) and a transparent ITO thin film (20 nm). When a positive voltage of a few volts is applied between the gate and the source, the WO3 thin film changes to a dark blue color and simultaneously becomes metal, and when a negative voltage is applied, it returns to a colorless transparent insulator.