Patent ID: 7122806

Claim:
A method for photo-ionizing atoms from a semiconductor or dielectric tip in an atom probe comprising the steps of: (a) providing a positive constant electric field from the tip to a negative electrode to extend atoms at the tip surface and to induce escape of surface atoms photo-ionized near the tip surface, wherein the magnitude of the electric field is held below the electric field required to produce thermal field evaporation of ions from the tip; and (b) providing a pulsed laser beam focused onto the tip to photo-ionize extended atoms on the tip, wherein the laser wavelength is selected to coincide with strong optical absorption in the semiconductor or dielectric tip material such that photo-ionization efficiency is enhanced, and wherein the thermal energy deposited by the laser into the tip is held less than the energy required to activate thermal field evaporation, thereby obtaining primarily non-thermal photo-ionization of atoms from a semiconductor or dielectric tip.