Process-structure-properties relationship in direct liquid injection chemical vapor deposition of amorphous alumina from aluminum tri-isopropoxide

Abstract

We propose a method to apply amorphous alumina films on the inner surface of glass containers aiming to improve their hydrothermal barrier property. We have carried out alumina deposition on Si substrates as a function of deposition temperature to determine the physico-chemical properties of the thin film materials, and on glass containers to evaluate the influence of post-deposition hydrothermal ageing on the films properties. Film preparation has been achieved by metal-organic chemical vapor deposition (MOCVD), using tri-isopropoxide aluminum (ATI) dissolved in anhydrous cyclohexane as precursor, in a temperature range between 360 °C and 600 °C. A direct liquid injection technology is used to feed the reactor in a controlled and reproducible way. The amorphous alumina films have been characterized by several techniques such as XRD, EPMA, XPS, SEM, AFM and scratch-test method. Films are amorphous and hydroxylated at 360 and 420 °C and close to stoichiometric at 490 and 560 °C. Hydrothermal ageing simulated by a standard sterilization cycle modifies the adhesion and surface morphology of the alumina film on glass containers to a rough, porous and non-adhesive layer. Elemental compositions of alumina films on Si substrates. O/Al atomic ratios (EPMA) for films processed in the horizontal (blue dots) and vertical (red dots) reactors. Carbon concentration for films deposited in the horizontal (black dots) and vertical (white dots) reactors, determined, respectively, by XPS and EPMA. Films processed at high temperatures (490-560 °C) are stoichiometric Al2O3 with a very low amount of hydroxyl groups. Carbon concentrations are lower than 1 at%.