摘要 |
A cathode is formed of an alloy, which includes 0.01 to 5 mol % of scandium and 0.01 to 0.3 mol % of alkali metal. Base of the alloy has a work function greater than or equal to 4 eV and is silver, aluminum, or indium or the alloy thereof. Thickness of the cathode is preferably 1 to 30 nm. Also, as a cathode protection layer, an aluminum alloy is formed on the cathode in a thickness greater than or equal to 50 nm, the aluminum alloy containing 0.1 to 5 mol % of silicon, copper, scandium and/or manganese.
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