Grid emission suppression characteristics of molybdenum grids coated with Hf and Pt films

Hf and Pt were deposited onto molybdenum grids by ion beam-assisted deposition (IBAD). Electron emission characteristics from these coated molybdenum grids contaminated by active electron emission substances (Ba, BaO) of the cathode were measured using the analogous diode method. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were performed on the surface of molybdenum grids coated with Hf and Pt films. When emission substances were deposited onto the grid surface, the reaction between BaO and Hf formed a BaHfO3 compound that markedly reduced the accumulation of BaO and accordingly decreased grid emission. The decomposition of BaO on the surface of Pt under high temperature was believed to lead to the formation of Ba and its re-evaporation from the surface, reducing active electron emission substances with a consequent significant reduction in grid emission. According to the comparison of their grid emission suppression mechanisms, it could be concluded that grid emission suppression was mainly the reduction of active electron emission substances on the grid surface, in particular BaO. This could be a worthwhile approach for the development of new grid coating materials.