Field evaporation of germanium under THz pulses: application to atom probe tomography

This study investigates the field evaporation behavior of germanium (Ge) under monocycle terahertz (THz) excitation using atom probe tomography (APT). The influence of THz pulse polarity, specimen geometry, and spectral content is systematically examined. Dual-polarity experiments reveal the coexistence of two emission mechanisms: field-driven and thermally assisted. Delayed evaporation features are observed, and their dependence on specimen geometry is analyzed using a nanowire heat diffusion model. The spectral filtering of the THz radiation further confirms the role of the pulse spectral content in shaping the thermal response of Ge samples. These findings identify key parameters governing THz-assisted APT of low-conductivity materials and provide guidelines for optimizing experimental conditions.