PHOTOELECTRON-SPECTROSCOPY STUDIES OF BARIUM FILMS ON DIAMOND WITH RESPECT TO THE MODIFICATION OF NEGATIVE ELECTRON-AFFINITY CHARACTERISTICS

Efficient low-field emission of electrons from diamond requires surfac e treatments that lead to the occurrence of a negative or low positive electron affinity. The deposition of caesium/caesium oxide films has produced some of the best field emitters to date, but such films have been shown to be thermally unstable. In order to investigate further t he nature and properties of deposited films, treatment of a single cry stal diamond (111) surface with barium has been carried out. The him t hickness and chemical composition have been determined and the electro nic properties ascertained, with particular focus on negative electron affinity behaviour. The thermal stability has also been probed. The p roperties of the Ba adlayers have been found to differ significantly f rom those of deposited Cs films. In particular, the nature of the reac tive interface between the metal and the diamond substrate is quite di ssimilar in both cases. Further, the barium overlayers are notably mor e stable with respect to heat treatment, with treated surfaces retaini ng negative electron affinity character, even after heating to beyond 1000 degrees C. (C) 1998 Published by Elsevier Science S.A.