Molecular dynamics simulation for emission and propagation of electrons in cathode nano-structures
Abstract
At the nano- and microscale the magnitude of parameters describing nonuniformity of a vacuumelectronic system may be considerable when compared to corresponding parameters describing the system under study. As an example, consider the interelectron spacing compared to tip radius in a field emitter array, the interval between successive electron emissions compared to transit time in a microdiode, or the size of crystal grain facets on the cathode surface compared to the cathode area. When such is the case, it is important to use modelling methods which can accurately and efficiently capture the discrete and stochastic nature of the physics governing the system. Irregularities on such a small scale can have considerable effect on electron beams on the larger scale: this is the primary meaning behind the often encountered statement that “intrinsic emittance cannot be corrected by subsequent beam optics”. For instance, concerning field emission, much of the emission comes from comparatively few nm-scale emission sites at the apex of emitters constituting a small fraction of the cathode surface. At those sites, defects in the crystal structure or the presence of impurities lower the local work function. Another example is the role that ions near to the cathode can play in enhancing the local electric field leading to spurious emission and even triggering breakdown because they contribute to Schottky lowering of the emission barrier. Molecular dynamics (MD) simulations are eminently suitable for modelling nano- and microscalevacuum electronics where irregularity and discrete particle effects play such an important role.Whether understanding devices that are entirely on the microscale, or understanding the dynamicsin a region surrounding a microstructure to understand its influence on macroscale behavior. Coupled with realistic electron emission models, these type of simulations offer an intriguing tool for better analysis and development of electron sources.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 24, 2019
- Source ID
- FA95501817011
Entities
People
- Á. Valfells
Organizations
- Air Force Office of Scientific Research
- Reykjavík University
- United States Air Force