Resonant Tunneling Behavior In Ion-Enhanced Field and Thermo-Field Emission

Under a high electrical field, field emission current may be significantly enhanced by positive ions very close to the cathode surface. In addition to distorting the potential field to both lower and thin the potential barrier, the ion can also induce resonant tunneling, which can be a major factor in the emission current. In this study, resonant tunneling behavior has been investigated using a simple model by solving the 1D Schrodinger's equation in the presence of an ion approaching the surface. Analysis shows that as the ion approaches the surface, resonant states move from lower to higher energies. Further, as the electric field increases, the resonant states move from higher to lower energies. Resonant contributions can be dominant under high applied field (similar to 0.5-3 V/nm) when the ion is close to the surface (similar to 0.5-3 nm). Under such conditions the resonances are located near the energy region that has highest differential emission current, which is proportional to the product of the supply function and the transmission probability. The results of this study suggest that it may be possible to control (maximize/minimize) the emission current by matching/ mismatching the supply function to the resonant states, which can be applied to various electron emission technologies.