Abstract: Provided is a Schottky emitter having the conical end with a radius of curvature of 2.0 ?m on the emission side of an electron beam. Since a radius of curvature is 1 ?m or more, a focal length of an electron gun can be longer than in a conventional practice wherein a radius of curvature is in the range of from 0.5 ?m to not more than 0.6 ?m. The focal length was found to be roughly proportional to the radius of the curvature. Since the angular current intensity (the beam current per unit solid angle) is proportional to square of the electron gun focal length, the former can be improved by an order of magnitude within a practicable increase in the emitter radius. A higher angular current intensity means a larger beam current available from the electron gun and the invention enables the Schottky emitters to be used in applications which require relatively high beam current of microampere regime such as microfocus X-ray tube, electron probe micro-analyzer, and electron beam lithography system.

Abstract: An electron gun used in a particle beam device, for example in an electron microscope, has a relatively good brightness and may be operated under vacuum conditions which can be easily achieved (i.e., for example, at a residual pressure of about 10?6 or 10?7 mbar). The electron gun comprises an electron source having an electron emission surface. Furthermore, the electron gun comprises a first electrode configured to control a path of electrons emitted from the electron emission surface, a second electrode which is configured to suppress emissions of electrons from a side surface of the electron source and a third electrode configured to accelerate electrons emitted from the electron source to a final energy. A first voltage, a second voltage and a third voltage are adjusted to avoid any crossover of electrons emitted from the electron emission surface.

Abstract: Provided is a Schottky emitter having the conical end with a radius of curvature of 2.0 ?m on the emission side of an electron beam. Since a radius of curvature is 1 ?m or more, a focal length of an electron gun can be longer than in a conventional practice wherein a radius of curvature is in the range of from 0.5 ?m to not more than 0.6 ?m. The focal length was found to be roughly proportional to the radius of the curvature. Since the angular current intensity (the beam current per unit solid angle) is proportional to square of the electron gun focal length, the former can be improved by an order of magnitude within a practicable increase in the emitter radius. A higher angular current intensity means a larger beam current available from the electron gun and the invention enables the Schottky emitters to be used in applications which require relatively high beam current of microampere regime such as microfocus X-ray tube, electron probe micro-analyzer, and electron beam lithography system.