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Due to its inherent flexibility reactive magnetron sputtering is a very attractive technique for the fabrication of thin compound films. When operated in the transition mode it is possible to growth stoichiometric materials with high deposition rates using cost-effective metallic targets.
Especially where the film composition plays an important role in achieving desired film properties it is of great interest to be able to reliably control the metal to reactive gas flux to the substrate. This is the case in transparent conductive oxides like ZnO and TiO2, where small changes in the oxygen content of the films have a strong effect on micro structure, optical and electrical properties.
A method using the current-voltage-pressure relationship of the reactive magnetron discharge for this purpose is discussed in this work. It is shown that there are two different groups of reactive discharges which can be classified by the ratio of the secondary electron emission coefficients of the metal and the corresponding oxide.
Each group shows a distinct current-voltage behavior, which demands a certain operation mode in order to stabilize the discharge in in the transition mode. This enables a fine control of oxygen partial pressure resulting in optimized films. Model experiments linking discharge parameters with film properties will be discussed in detail.