Two-step electron tunneling from confined electronic states in a nanoparticle

Sequential two-step electron tunneling from nanoparticles has been studied from a transport point of view. A steady-state balance equation for the partial electron currents is derived and solved to obtain the stationary level occupancy, which leads to the overall tunneling current as a function of the applied field. Our model explains the steplike features observed in high field tunneling experiments involving composite cathodes that incorporate electronic quantum-confinement regions. In order to assess the validity of our model and to show the apparition of the steplike features in field-emission experiments, we have used the usual diode configuration to obtain current-voltage characteristics from a composite cathode. The theoretical model presented in this paper shows qualitative agreement with the experimental data.