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Mg O SECONDARY ELECTRON EMISSION FILM PREPARED BY RADIO-FREQUENCY REACTIVE SPUTERRING
Author(s): 
Pages: 10-16
Year: Issue:  1
Journal: Acta Metallurgica Sinica

Keyword:  radio-frequency reactive sputteringthickness of filmsurface roughnesssecondary electron emission coefficientresistance to electron beam bombardment;
Abstract: High, stable and durable secondary electron emission is an essential property for the application of dynodes of electron multipliers and photomultiplier tubes. The Mg O film have been widely used as dynode materials for the applications owing to its good secondary electron emission properties. In this work, Mg O and Co O doped Mg O films, as secondary electron emission films, were prepared by radio-frequency reactive sputtering deposition on the stainless steel substrate, and also another Mg O film at the surface of activated Ag Mg alloy was prepared. The effect of preparation processes on the secondary electron emission properties of the films was focused.It was found that the film thickness significantly affected the resistance to electron beam bombardment. With the increase of film thickness, the resistance to electron beam bombardment was significantly enhanced. Radio-frequency reactive sputtering deposition could control the film thickness by varying deposition time. The surface quality of Mg O film is quite sensitive to the oxygen partial pressure of the deposition atmosphere. Higher oxygen partial pressure caused higher surface roughness, which was harmful to the secondary electron emission. After doping with Co O, the surface of Mg O films were much flatter and smoother, resulting in the improvement of the secondary electron emission coefficient. The Co O doping also reduced of the sensitivity of film surface quality to the oxygen partial pressure. The secondary electron emission coefficient of Co O doped Mg O film sharply decreased after heated at 550 ℃ for 1 h due to the surface quality degrading and the thermal decomposition induced loss of oxygen. Elevating the substrate temperature or oxygen partial pressure during deposition accounted for the presence of metallic Mg in film and the degrading of surface quality, which finally lead to lower secondary electron emission coefficient.
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