Designing a two-stage acceleration lens for a 100 keV single-ion implantation system

An array of color centers, each known as an NV center formed by a single-nitrogen atom and a vacancy, spaced at intervals of several tens of nanometers in a diamond exhibits quantum entanglement effects and indicates potential for quantum device applications. To fabricate such an array by implanting single-nitrogen ions into a diamond, a 100 keV single-ion implantation system (SIIS) has been developed by combining a linear Paul-trap laser-cooling ion source (LPTLC-IS) with a sympathetically cooled ion technique and a two-stage acceleration lens. So far, the LPTLC-IS and the two-stage acceleration lens have been refined as individual elemental technologies. However, for deterministic single-ion implantation, the SIIS must meet the following ion beam conditions: implantation with nanometer accuracy, a long working distance exceeding 100 mm to accommodate a quantum effect detector, and a penetration depth of approximately 100 nm in a diamond. These requirements necessitate the development of a two-stage acceleration lens capable of focusing the ion beam to a width of < 50 nm without a collimator when using a 100 keV ion beam. In this study, the two-stage acceleration lens, comprising 1st and 2nd acceleration lenses, was redesigned using numerical simulations to optimize lens parameters. Our primary redesign focus was the 2nd acceleration lens, which was redesigned based on the configuration of the previously developed lens. The resulting two-stage acceleration lens successfully met the target beam conditions for the SIIS.