Ion implantation and transmission microscopy with nanometer resolution using a deterministic ion source
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Abstract
This work reports on the construction and setup of a single ion source experiment on the basis of a linear Paul trap to the aim of deterministic ion implantation and single ion microscopy. Single 40 Ca + ions at energies ranging from 0.3 to 6 keV were extracted from the trap at a maximum rate of 3 ions per second. The beam divergence was measured to be 23.7 ± 2.5 μrad, at an energy dispersion of 174 meV, limited by the noise of the extraction voltage. Focussing of the beam with an electrostatic einzel lens to a 1-σ radius of 5.8 ± 1.0 nm was demonstrated, where the minimum two-sample deviation of the beam position in the focal plane has been determined to be 1.5 nm, when integrating over a period of 9 hours.
For the purpose of single ion implantation, molecular nitrogen ions were trapped and sympathetically cooled. Subsequent extraction and implantation of these ions has been carried out and the creation of single nitrogen vacancy colour centres in diamond by this method was shown.
For the first time, a single particle microscope was realised, which employs deterministically extracted calcium ions as probe particles for transmission imaging. Even when used in combination with an imperfect detector, this showed a 5 times higher signal-to-noise ratio as compared to microscopy with a conventional particle source, which is subject to Poissonian emission properties. Moreover, it was demonstrated, that the gain in spatial information can be maximised by employing the Bayes experimental design technique, when imaging structures with a parametrisable transmission function. In addition, the precise timing of the extraction event was used to gate the detector and in this way suppress detector dark counts by 6 orders of magnitude.
Furthermore, various future applications of the deterministic single ion source for novel types of microscopy or material doping are discussed.