Alterations in Surface Films, Diffusion and Dissociation

The diffusion can considerably interfere with the build-up of the equilibrium, and also strongly influence the thickness of the affected layer. Various processes can cause the diffusion  

An Ag-Cu target can serve as example. With a target temperature of 80°C the equilibrium is achieved after 40 min. However, with a target temperature of 270°C the equilibrium is not achieved before 200 min, and the corresponding thickness of the 

The dissociation energy of chemical compounds is in the order of 10 to 100 eV. Of course, such a compound can be expected to decompose if bombarded with keV ions. Part of the volatile products thus arising are pumped away with the sputtering gas so that the growing film shows a deficit of these components. This is why stoichiometric compound films as oxides, nitrides, sulphides, etc. usually can only be prepared by sputtering by the addition of small amounts of O2, N2, H2S, etc., to the sputtering gas, hence in a form of reactive sputtering which replaces the losses. 

---