A method for atom probe tomography (APT) sample preparation from a three-dimensional (3D) field effect transistor device formed within a semiconductor structure is provided. The method may include measuring a capacitance-voltage (C-V) characteristic for the 3D field effect transistor device and identifying, based on the measured capacitance-voltage (C-V) characteristic, a Fin structure corresponding to the 3D field effect transistor device. The identified Fin structure is detached from the 3D field effect transistor device using a nanomanipulator probe tip. The detached Fin is then welded to the nanomanipulator probe tip using an incident focused ion beam having a voltage of less than about 1000 eV. The incident focused ion beam having a voltage of less than about 1000 eV is applied to a tip of the Fin that is welded to the nanomanipulator probe tip.