Plasma discharge efficiency increase by using a small bandgap protective layer material- first-principles study for Mg1 -x Zn x O

In this work, the properties of Mg1-xZnxO thin films are investigated as an example of a protective layer material with a small bandgap in a plasma display panel, to analyze the impact of these kinds of materials on the discharge properties. Using the first principles calculation method, the electronic structure of Mg1-xZnxO crystal is analyzed, and an analytical formula is obtained for the values of the bandgap. A cubic structure is obtained for x between 0 and 0.625. The secondary electron emission coefficients γ of Neon and Xenon with the Mg1-xZnxO films are then evaluated based on Hagstrum’s theory. The γ value for Xe ions is zero, until a concentration of 0.375 is reached, when the bandgap is about 5.1 eV. At x = 0.375 and beyond the condition for Auger emission by xenon ions is fulfilled, and for x > 0.375 the γ value increases continuously until a value of 0.07 is reached for x = 0.625. The γ value for Ne increases from 0.25 to 0.38 when the ZnO proportion is increased from 0 to 0.625. The discharge characteristics of the SM-PDP with Mg1-xZnxO protective layer are then calculated using the fluid model. When increasing the x value, the working voltage is strongly reduced, while the discharge efficiency is enhanced by about 60% at 20% Xe for a change in x from 0 to 0.625. We find that this increase is mainly caused by increased electron excitation efficiency. Therefore mixed-oxide materials with a small bandgap like MgO-ZnO in principle enable the use of high xenon content plasma displays, while strongly increasing the discharge efficiency.