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Platinum Metals Rev., 1998, 42, (1), 10

Cold Platinum Cathode


Field emission displays which use cold cathodes to generate the electron beam are highly suitable for future flat panel displays as they provide complete colour capability, have a large viewing angle and are cost efficient. But until now, cold cathodes have produced an electron emission efficiency of less that one per cent.

Now, however, a team from Pioneer Electronic Corporation, Japan, has developed a cold cathode with a greatly increased electron emission efficiency using a Pt/SiOx/Si/Al structure on a thermally oxidised silicon substrate (N. Negishi, T. Chuman, S. Iwasaki, T. Yoshikawa, H. Ito and K. Ogasawara, Jpn. J. Appl. Phys., Part 2, 1997, 36, (7B), L939–L941).

The silica and silicon films, 400 nm and 5 μm thick, respectively, and platinum, 10 nm thick, were deposited onto a 300 nm thick film of aluminium, with the platinum and aluminum films used as the cathode electrodes. The electron emission was evaluated using a glass plate coated with a transparent electrode of indium-tin oxide and phosphors as anode and screen, respectively.

At room temperature and with an applied voltage of 110 V and accelerating voltage of 5 kV, an electron emission efficiency of 28 per cent was achieved together with brightness for green emission of 80 kcd m 2, using ZnS:Cu,Al. The high emission efficiency may be closely linked to the occurrence of negative resistance.