Nanoscience and Nano Technology

Biography

Biography: Nikolaus Stolterfoht

Abstract

After the first observation that keV ions are guided through insulating nano­capillaries, the topic has received consid­erable attention during the past decade. These capillaries are nanotubes with a diameter of about 100 nm and a length of about 10 µm. The essential property of the capillary guiding is a self-organizing process, which governs the charge deposition inside the capillaries. With increasing deposition of the ions, the charge patch increases until the electrostatic field is large enough to deflect the ions. At equilibrium, the ions are guided maintaining their incident charge state. Milestones of the field concerning experiments and simulations are presented in accordance with a recent review over the field of capillary guiding. Experiments are described giving emphasis to the guiding of highly charged ions in the keV energy range. Recent experiments with a single straight macrocapillary are treated allowing for the control of conductivity by changing the temperature of the material. Single tapered capillaries are discussed involving an enhance­ment of the beam density and the production of a microbeam for biological applications. These studies have motivated several groups devoting efforts to the production of a beam with diameter of the submicron scale. Apart from the experimental studies, theoretical concepts of the capillary guiding are discussed. Calculations using a drift model for trajectories and charge distributions for 4.5-keV Ar⁷⁺ incident under 0° and 1° into a conical microcapillary were shown in Figure-1. The simulations show that the density of the transmitted ions is enhanced by a factor as large as 4. These results are of importance for the biological applications mentioned. Altogether, it is elucidated that capillary guiding involves several novel phenomena whose understanding has made essential progress.