Positron annihilation studies of defects in PVD TiN coatings

The performance of thin films is generally controlled by their microstructure since this will dictate the particular range of properties which the coating exhibits. Indeed, by control of microstructure using the process parameters available in most deposition technologies (substrate temperature, energy and intensity of ion bombardment etc.) it is possible to optimise the properties of a coating for a given application. However, to achieve the best results it is necessary to have an appropriate nondestructive structural probe by which to assess the microstructural changes. Positron annihilation spectroscopy is an attractive technique to achieve this where the films contain small open defects such as intercolumnar voids or vacancies. This paper will present some recent results on the use of the technique to characterise titanium nitride films deposited by several different deposition technologies and will highlight the effect of defect density and columnar packing density on the results generated.