Secondary electron emission from a cathode material in an AC plasma display panel (PDP) is dominated by potential emission mechanism, which is sensitive to band structure of a protective layer. Therefore, the secondary electron emission property can be modified by a change in the energy band structure of the protective layer. Mg2-2xTixO2 films were prepared by an e-beam evaporation method to be used as possible substitutes for the conventional MgO protective layer. The oxygen content in the films and in turn, the ratio of metal to oxygen gradually increased with increasing TiO2 content in the starting materials. The stress relaxation, when the [TiO2/(MgO + TiO2)] ratio in-the evaporation starting materials was 0.15, seems to be related to the rough surface grown by Stranski-Krastanov mode due to the poor lattice matching condition between substrate and film. The film density, which was calculated from the refractive index, had a maximum at the [TiO2/(MgO + TiO2)] ratio of 0.15 and then gradually decreased with a further increase in the [TiO2/(MgO + TiO2)] ratio in the starting materials. When the [TiO2/(MgO + TiO2)] ratios of 0.1 and 0.15 were used, the deposited films exhibited the secondary electron emission yields improved by 50% compared to that of the conventional MgO protective layer.