Linking Energy-Loss Mechanisms to Dark Contrast for the Emission of Dynamic Secondary Electrons

Spatial and temporal exploration of charge carriers with secondary electrons emitted from surfaces and interfaces of materials offers novel and complementary opportunities for deepening our knowledge about charge transport in real space and time for technologically relevant device applications, ranging from electronics to optoelectronics and plasmonics. The time-resolved signal contrast obtained from these explorations depends on the detailed mechanisms of internal electrons escaping from materials systems, yielding either bright or dark image contrast. However, a deeper microscopic understanding of an element-specific structure-property relationship leading to different dynamic signal contrast remains largely elusive. Here, we present the results of coupled-rate-equation-based model simulations, and discuss the energetics of the internal electrons and energy-loss mechanisms along with effective probe length scales, to account for the dark contrast of emitted secondary electrons observed in semiconducting materials systems.