Date of Award
Master of Science in Electrical Engineering - (M.S.)
Electrical and Computer Engineering
Ken K. Chin
Roy H. Cornely
In this thesis, exact calculation and computer simulation of an atomically sharp emitter are presented. In the theoretical analysis, the cathode-anode or cathode-gate complex is modeled for cone- and wedge-shaped emitters so that exact solution can be obtained. The exact solution reveals that the field on the emitter surface depends not only on the sharpness of the emitter, but also on the global geometry of the field emitter, gate, and anode complex. This finding is contrary to a widely accepted concept that field is predominantly determined only by local curvature of the tip.
The theoretical results are confirmed by computer simulation of the field distribution of realistic tip-gate-anode structures.. In our study the emitter is atomically sharp, with a radius as small as lnm, while the emitter-gate distance, the gate-anode distance, and the supporting structure of the emitter tip, are in the range of 2000 - 5000nm.
To accommodate more than three orders of difference between the dimension of the tip area and that of the tip support height and tip-gate distance, the ANSYS Software which uses finite element method has variable mesh sizes. Our finite element simulation results agree with other simulation results published earlier in this field. Since the mesh size can be as small as mnm and by using virtual memory the element number can be as big as 4000, it is expected that our result is more accurate than the calculation presented in reference.
As a result of our calculation it was possible to give several design guidelines for the selection of emitter parameters such as the tip radius, the emitter-gate distance or gate diameter, and the emitter shaft's half angle. Furthermore, the effect of mesh size on our simulation results are discussed.
Cheng, Ziyan, "Analysis of electric field on surface of an atomically sharp field emitter" (1992). Theses. 2239.