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AFRL Demonstrates Transparent ZnO Electronics

WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- AFRL scientists demonstrated transparent microelectronic circuits using nanocrystalline zinc oxide (ZnO) transistors. Large-area electronics for electromagnetic, chemical, and mechanical sensors, as well as large-display electronics, can be more useful in compact system applications such as unmanned air vehicles (UAV) if the sensors are also invisible. Such circuits allow simultaneous use of the same surface area for optical and electronic (microwave) apertures. The current technology is incompatible with transparency requirements because both the semiconductors and metal interconnects are nontransparent. Some thin-film electronics used in commercial display electronics that make use of amorphous/polycrystalline silicon or organic semiconductors have very poor electronic performance, due primarily to the extremely low electron mobilities characteristic for these materials.

The AFRL in-house research demonstrated the viability of using nanocrystalline ZnO films to fabricate high-performance transparent electronic circuit components on transparent glass substrates. Building upon previously conducted in-house research on ZnO-based electronics, laboratory scientists fabricated circuits containing field-effect transistors, conductors, and passive components that are highly transparent in the visible spectrum. This technology employs low-temperature process steps that are compatible with large-area transparent organic substrates that can also be flexible. Possible applications of this new technology include helmet-mounted display electronics, shared-aperture sensors for UAVs, invisible sensor electronics for unattended ground sensors, and invisible radio frequency identification tags for battlefield management.