Nitride -based Cold Cathodes for Microdevice Applications

University Of Houston, Houston TX

Investigators

Abstract

The project develops nitride-based cold cathode electron emitters capable of operating under near-atmospheric pressure and in chemically active environments, and works out commercially feasible fabrication techniques for these devices. Efforts will be concentrated on nanocrystalline boron/carbon nitride (BN/CN) materials. These are excellent candidates for field emitter devices, with low turn-on field strengths and high emission currents, even in relatively high-pressure regimes. Both show excellent chemical, thermal, and mechanical stability, high sputtering resistance, and, therefore, longer cathode lifetimes. They are compatible with conventional silicon substrates, allowing straightforward device integration with excitation circuitry, amplifiers, and signal conditioners. They are superior alternatives to diamond and other carbon-based thin films, being easier to deposit and pattern, and more resistant to attack by oxygen and water vapor. Some of the critical electronic properties will be optimized by post-growth modification techniques. Ion implantation and irradiation with x-rays and excimer lasers will be used to lower the threshold voltage, without detrimental changes to emission stability. We will also model the electron emission process in these films. Our model will cover electron injection from the substrate to the emitting layer, electron transport through the material, and finally emission into the vacuum. Naturally, we expect the modeling and characterization phases of the study to feedback to each other, ultimately resulting in an effective tool for device design. The final stage of the project will be development of a nitride-based pressure sensor. In contrast to current technologies, these microsensors should allow precise, accurate and reproducible pressure measurements over many decades of pressure. They also have the potential for integration in corrosive and high temperature environments. Finally, the drive and sensing electronics, which could be integrated on the same chip, can be significantly simpler than what is currently needed by conventional capacitive and piezoelectric sensors.