Terahertz-driven electron field emission and ion field evaporation: application to Atom Probe tomography

Single-cycle terahertz (THz) pulses have been used to drive electron emission from biased and unbiased metallic nanotips. The electron emission yield and the maximum electron energy are linked to the THz near-field. Recently, the development of similar approaches to drive ions emission was reported. Field emission of positive ions from a nanometric tip (called field evaporation) is the basic principle of the Atom Probe Tomography, which is a 3D imaging technique based on controlled field evaporation of atoms from a nanometric needle shaped sample under a strong electric field.Here we report on the use of single-cycle THz pulses to emit electrons and ions from nanometric tips. The THz source used in our experiments is a homemade laser based on two-color plasma generation. By election emission, the temporal shape of the THz near-field signal is measured as a function of the relative time delay between the THz pulse (pump) and the near infrared pulse (probe). Changes of the temporal shape of the THZ near-field signal are associated with a bandwidth reduction due to the filtering properties of the metallic tip. In the case of positively biased nanotips the enhancement of terahertz field allows to trigger the emission of positively charged ions from the nano-tip. Based on this effect, we demonstrate a high-chemical and spatial resolutions terahertz-assisted APT instrument.