Secondary Electron Emission Characteristics of Heavy-Metal Oxide Coatings for CRT Shadow Mask

Abstract

In order to reduce the misalignment caused by the thermal expansion of the shadow mask originated from the deposition of the primary electron energy, the secondary electron emission (SEE) characteristics of Bi2O3 and Fe3O4 coatings for the CRT shadow mask are studied. The total SEE yield of the Bi2O3 coating varies from 0.96 at a primary electron energy of 15 keV to 0.75 at 30 keV. These values are about twice as high as those of the Fe3O4 coating. The backscattered electron yield of the Bi2O3 coating increases almost linearly from 0.36 at a primary electron energy of 15 keV to 0.40 at 30 keV. That of the Fe3O4 coating also increases in the same manner, although its magnitude is much smaller. These measured values agree with the estimated values from the reported data which give the SEE yield as a function of the atomic number. The average energy of the backscattered electrons can be also estimated to be about 24% of the incident primary energy for the Bi2O3 coating, and 12% for the Fe3O4 coating. These results shows that the Bi2O3 coating effectively reduces the deposition of primary electron energy onto the shadow mask by the backscattering of incident primary electrons. Therefore, the Bi2O3 coating will result in the reduction of the temperature rise and the thermal expansion of the shadow mask to a greater extent than the Fe3O4 coating.