Growth regimes in pulsed laser deposition of aluminum oxide films

Alumina is technologically exploited in several forms, ranging from compact hard films as protective coatings to open microstructures of high specific area as supports for catalysts. Currently, various production processes are used to deposit the different forms. PLD has the potential of obtaining not only the different forms, but also a continuous modulation of properties, by tuning of the process parameters. This work investigates the relationship between the process parameters and the resulting film morphology, structure and properties for PLD performed with an alumina target in a background oxygen atmosphere. Three distinct growth regimes are found, leading, respectively, to compact homogeneous films, columnar structures and open microstructures. These structures are quantitatively characterized, and the ranges of the process parameters corresponding to the three regimes are identified. An empirical scaling law is proposed, which can be exploited as a guide for the design of growth processes aimed at obtaining specific film properties.