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UNIVERSITY OF UTAH
ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT
DISSERTATION DEFENSE FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
Advisor: Massood Tabib-Azar
Microplasmas are currently used in displays, two-terminal breakdown switches, light sources and medical instruments. They can also be used in miniaturized particle accelerators, micro X-ray generators, UV and extreme UV sources, gas sensors and in micro-propulsion thrusters. They are also excellent candidates for applications in harsh environments that usually lead to the breakdown of silicon electronics. Here we develop their unique applications in X-band microwave analog and digital devices and circuits. To enable these applications, we identified a breakdown region, called sub-Paschen regime, that enables generation of atmospheric plasmas at low voltages. The sub-Paschen regime involves devices with breakdown gap below 10 mm in 1 atmosphere in air. This newly discovered operation regime enabled us to design plasma devices with relatively low operation voltages of 50-100 V.
We developed micro-plasma devices similar to MOSFETs with drain, source, gate regions that used plasma channels for switching or amplification. The gate field effect was successfully tested under both dc and ac excitations. Drain current modulation frequency up to 7 GHz was obtained. Additionally, we implemented logic gates with microplasma devices to realize simple Boolean logic operations including OR, AND, NOT and XOR. The gates were then combined to obtain a 1-bit half-adder circuit. The MOPFET developed in this work achieved 3x reduction in the breakdown (device turn-on) voltage by operating in the sub-Paschen regime. In addition to the scaling in breakdown voltage, the MOPFETs are at least 50x smaller compared to plasma transistors reported in the past. The smallest MOPFET used in this work had a source-drain gap of 1 µm and showed unprecedented functionalities derived from plasmas at a micro scale.
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This past year our faculty have received funding, contracts, and awards from such resources as the CIA, NSF, AFOSR, and DARPA.
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