The mechanism of TiO 2 deposition by direct current magnetron reactive sputtering

Abstract

Thin films are generally thought of as being the product of a reaction between the surface and atoms and/or molecules in the gas phase. However, a relatively new theory, the theory of charged clusters (TCC), suggests that charged clusters nucleate in the gas phase and become the growth unit for a thin film. The aim of this study was to determine whether or not TiO 2 thin film deposition by DC reactive sputtering occurs via this mechanism. TiO 2 was deposited on unheated transmission electron microscopy grids to observe TiO 2 clusters, as well as glass and silicon substrates to observe the resulting thin films. The results showed that TiO 2 clusters were indeed produced in the chamber of a direct current reactive sputtering system. Furthermore, these clusters were observed as close as 50 mm away from the target. Clusters 3 nm and <2 nm in diameter were found 250 mm and 50 mm away from the target, respectively The cluster size was found to have a direct effect on the film deposited. Smaller clusters produced a facetted crystalline anatase film whereas larger clusters produced an amorphous film.