Capillary nitrone
A capillary nitrone is a device for generating ion and atomic beams.
construction
The capillary nitrone, the basic concept of which was published in 1981, consists of a fine metal capillary through which gas flows as an anode and an extraction cathode concentric to it with an outlet opening . When a high voltage is applied (usually a few kilovolts ), a gas flow through the capillary is ionized by free electrons and secondary electrons , which are accelerated towards the anode (see also impact ionization ). The positively charged ions are accelerated in the electric field and form an ion beam behind the opening of the extraction cathode . Due to recombination and charge exchange processes in the plasma , the beam partly also consists of uncharged atoms .
The capillary is usually made of resistant materials such as tungsten . The quartz capillary nitrone represents a further development from 1992. Here the capillary consists of quartz , an electrically insulating material , into which a metal wire is inserted to generate the anode potential. The advantage lies in the simpler, more flexible and cheaper production of quartz capillaries with a given inner diameter , which, unlike metal capillaries, are not laboriously drilled , but can be electrochemically etched free or pulled by a glassblower .
As a rule, noble gases are used as operating gases , as they only undergo a slight chemical reaction with the other materials involved. A capillary nitrone also works with hydrogen , nitrogen or even air .
With ion beams, current densities of up to 100 A / cm² and beam currents of several milliamperes are achieved.
Areas of application
With the ion and atomic beams, surfaces can be sputtered over large areas. With atomic beams, insulating surfaces can also be processed. If ion beams were used, such surfaces would become more electrostatically charged, which would slow down the ions before they hit the surface.
By focusing with ion optics , beams with very high power densities can be generated in a high vacuum , with which surfaces can also be processed selectively.
literature
- John F. Mahoney, Julius Perel, A. Theodore Forrester: Capillaritron: A New, Versatile Ion Source. In: Appl. Phys. Lett. 38, 1981, pp. 320-322 ( doi : 10.1063 / 1.92355 ).
- John F. Mahoney, Dan M. Goebel, Julius Perel, A. Theodore Forrester: A Unique Fast Atom Source for Mass Spectroscopy Applications. In: Biomed. Mass. Spectrom. 10, 1983, pp. 61-64 ( doi : 10.1002 / bms.1200100203 ).
- Markus Bautsch, Patrik Varadinek, Stephan Weg, Heinz Niederig : A Compact and Inexpensive Quartz Capillaritron Source. In: J. Vac. Sci. Tech. A. 12, No. 2, 1994, pp. 591-593 ( doi : 10.1116 / 1.578839 ).
- Markus Bautsch: Scanning tunnel microscopic examinations on metals atomized with argon. Chapter 4: Structure and properties of the quartz capillary nitron. Verlag Köster, Berlin 1993, ISBN 3-929937-42-5 (Technical University Berlin, dissertation, 1993).