MgO SECONDARY ELECTRON EMISSION FILM PREPARED BY RADIO-FREQUENCY REACTIVE SPUTERRING

High, stable and durable secondary electron emission is an essential property for the application of dynodes of electron multipliers and photomultiplier tubes. The MgO film have been widely used as dynode materials for the applications owing to its good secondary electron emission properties. In this work, MgO and CoO doped MgO films, as secondary electron emission films, were prepared by radio-frequency reactive sputtering deposition on the stainless steel substrate, and also another MgO film at the surface of activated AgMg 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 MgO 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 CoO, the surface of MgO films were much flatter and smoother, resulting in the improvement of the secondary electron emission coefficient. The CoO doping also reduced of the sensitivity of film surface quality to the oxygen partial pressure. The secondary electron emission coefficient of CoO doped MgO film sharply decreased after heated at 550 °C for 1 h due to the surface quality degrading and the thermal decomposition induced loss of oxygen. Ele*收到初稿日期: 2015-04-02,收到修改稿日期: 2015-07-20 作者简介:王彬,男, 1988年生,博士生 DOI: 10.11900/0412.1961.2015.00189 第10-16页 pp.10-16 第 1期 王 彬等:射频反应溅射制备MgO二次电子发射薄膜 vating 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.