Methods of reactive magnetron sputtering using the sequential oxidisation of a sputtered metal film from two magnetron sources, in a rotating substrate system, have been developed. A rotation rate of around one revolution per second enhanced atomic level mixing of the film constituents on the substrate. Depending on the materials involved, two very fast feedback methods were employed to automatically control the admission rate of oxygen into the sputtering system. These methods were plasma emission monitoring (PEM), which was used to control the reactive sputter-deposition of In, Zn, W, V, Mo and Ti oxide, and voltage control, which was used to control the reactive sputter-deposition of Zn, Cu, Pb and Al oxide. The stoichiometry of the film was controlled by PEM or voltage control on one magnetron, and dopants were added by sputtering from the other magnetron. In other words, the former magnetron served two purposes; the first was to sputter metal and oxidise it, and the second purpose was to oxidise the metal sputtered from the other magnetron.