Focused Ion Beam Milling with Cold Rubidium

Focused ion beams (FIB) from laser-cooled atoms promise important advances in ion microscopy and nanofabrication. Low temperatures enhance beam brightness and enable higher resolution imaging and milling. More than 30 elements can be cooled, allowing for high brightness sources for many new ion species.

A FIB apparatus using laser-cooled rubidium has been developed for nanofabrication and imaging. We aim to achieve a higher beam brightness and a smaller focus spot size than commercial gallium FIB systems. The ion source is designed to achieve brightness in excess of 10^7 A m^−2 sr^−1 eV^−1, while maintaining sufficient beam current.

The cold atom ion source uses a vapour loaded 2D magneto-optical trap and polarization gradient cooling. Two-step photoionization allows control over the ionization volume and beam energy [1], maximizing beam brightness. This ionization scheme can be adapted to allow for unique capabilities including: coincident electron/ion detection and feedback for high-fidelity heralding of ions [2]; Rydberg exceptional state field ionization for reducing beam energy spread and chromatic aberration; and Rydberg blockade for isolating single ions.

[1] A.J. McCulloch et al., Phys. Rev. A, 95, 063845, (2017).

[2] A.J. McCulloch et al., Phys. Rev. A, 97, 043423, (2018).