Structure and secondary electron emission properties of MGO films deposited by pulsed mid-frequency magnetron sputtering

MgO thin films have been successfully prepared by a reactive dual-magnetron sputter technology using a sine wave power supply in a vertical in-line plant. Mg targets with a length of 400 mm were sputtered in an argon-oxygen atmosphere. The layers were deposited onto silicon as well as onto float glass substrates under various conditions. The oxygen flow into the discharge was controlled via fast piezo-valves in order to stabilise the process in the transition mode. The influence of the oxygen flow rate on the structure and properties of the films were systematically studied at a constant Ar flow rate (120 sccm) and a constant total pressure (0.4 Pa). The microstructure and mechanical properties of the films were investigated by X-ray diffraction and atomic force microscopy. Furthermore, the results of measured secondary electron emission of the MgO films will be presented. The samples possessed a very low optical absorption of about k = 10(exp -4) and a refractive index of 1.73 which nearly equals the bulk value. This is confirmed by the high mass density of 3.54 g/cm(exp 3) - 3.55 g/cm(exp 3). The structural properties are discussed in terms of the adatom mobility, which is found to be mainly influenced by the oxygen partial pressure. The high secondary electron emission coefficient up to 0.1 in combination with a high deposition rate of 35 nm.m/min support the capability of the films for the application in plasma display panels.