Dynamics of a Field Emitted Beam From a Microscopic Inhomogeneous Cathode

Abstract

We investigate by molecular dynamics simulations [1,2] a beam of electrons released via field emission from a planar cathode surface of 1 µm 2 with an inhomogeneous two-level work function, φ low and φ high . A rectangular grid, where each cell can have one out of two values of the work function, is used as a model. The number of cells in the grid ranges from 6x6 to 96x96. We compare a periodic checkerboard arrangement with disordered distributions of patches. We perform multiple simulations and randomize the pattern each time. We study the beam behavior by calculating the position and velocity of each electron, r.m.s. emittance, and the brightness of the electron beam. The emittance increases while brightness decreases, with the mean distance between patches with φ low when they are in minority, and they switch the behavior vs. the mean distance between patches with φ high when these patches are in minority, respectively. The Coulomb interaction between all particles is fully included in our simulations.

Edge effect on the current-temperature characteristic of thermionic cathodes

“…Finally, we perform high-resolution molecular dynamics simulations that include full Coulomb interactions of electrons. The method allows not only to specify the spread and density of the whole beam in the gap, but also of beams originating from particular areas of the cathode, and thus determine currents (including partial currents) and beam quality factors [19,20].…”

Space-Charge Limited Current from a Finite Emitter in Nano- and Microdiodes

“…Emission from the cathode is restricted to a circular area of radius, R. Electrons are emitted with negligible emission velocity. Electron emission and propagation is calculated using the same molecular dynamics approach for simulating space-charge limited dynamics as in previous papers from our research group [15][16][17][18] . In short, the algorithm is the following: An emission site is randomly selected on the emitting area of the cathode.…”