Date of Award

Spring 1998

Document Type


Degree Name

Doctor of Philosophy (PhD)


Electrical & Computer Engineering

Committee Director

Karl H. Schoenbach

Committee Member

Hani E. Elsayed-Ali

Committee Member

Gary E. Copeland

Committee Member

Ravindra P. Joshi


Field emission of electrons is the major cause of electrical breakdown in high voltage systems in vacuum. The highest hold-off electric field of the carefully polished and cleaned stainless steel cathodes was increased to 70MV/m. Thin silicon monoxide, SiOx, cathode coatings reduced field emission and increased the hold-off field further. Coating the stainless steel cathodes with 2μ SiOx reduced the field emission current by at least two orders of magnitude at field of 50MV/m and increased the breakdown field to 140MV/m, doubling the breakdown voltage.

The increase in hold-off voltage with SiOx coatings is discussed in terms of electron transport within the coating. Measurements indicate that current in SiOx at high fields is controlled by Frenkel-Poole electron emission from deep centers located about 1eV below the conduction band. Field emission current is limited at the coating-vacuum interface due to an accumulation of filled electron traps.