PURPOSE: To improve electron emission efficiency by forming insulator layers other than projections made of a conductor into nearly the same plane, and forming a gate electrode conductor layer thick.
CONSTITUTION: A conductor layer 2 for a signal electrode is formed on an insulating substrate 1, and projections 3 made of a conductor and formed at the desired interval and arrangement are provided on it. An electron permeating thin-film insulator layer 4 is formed on the projections 3, and the insulator layer 4 is formed into nearly the same plane as an insulator layer 5 at portions other than the projections 3. When voltage is applied to the conductor layer 2 and a conductor layer 6b for a gate, edge portions of the projections 3 made of a conductor have the strong electric field, and tunnel electrons with large energy are emitted from the conductor layer 6a. Since a conductor layer 6b outside the conductor layer 6a is thick, electrons are not diverged obliquely outward but emitted forward, and electron emission efficiency is improved.
KANEKO AKIRA
SUGANO TORU
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