A study of the physical properties and electrochemical behaviour of aluminium nitride films

Abstract

Thin films of aluminium nitride (AlN) were deposited onto glass substrates by reactive sputtering. Various N 2 partial pressures were used to produce films the composition of which ranged from pure aluminium to stoichiometric aluminium nitride. X-ray diffractometry, electrical resistance measurements and electrochemical tests were carried out to characterize these films. The XRD patterns show that the films are stoichiometric (N/Al=1) for a nitrogen partial pressure PN 2=1.33 × 10 −2 Pa. From XRD patterns and electrical resistance values of the films, we have demonstrated that for under-stoichiometric films PN 2 <1.33 × 10 −2 Pa, N/Al<1)), the structure goes through an intermediary state where both metallic (Al) and ceramic (AlN) phases take place. The electrochemical behaviour of the films was studied in H 2SO 4 and HCl solutions using classical electrochemical techniques as impedance diagrams and polarization curves. The results allow the proposition of a model for the under-stoichiometric films, which describes a contact between the metallic phase of Al and ceramic phases of AlN. When N 2 partial pressure is increased, the corrosion resistance of the films is also increased. The stoichiometric AlN films PN 2 = 1.33 × 10 −2 Pa)) show a corrosion resistance superior by several orders of magnitude to those of the under stoichiometric ones.