Ar stabilisation of the cubic/tetragonal phases of ZrO2 in thin films prepared by ion beam induced chemical vapour deposition

ZrO2 thin films have been prepared at room temperature by ion beam induced chemical vapour deposition (IBICVD). Two different sets of samples have bee n prepared depending on whether O-2(+) or mixtures O-2 + Ar+ ions were used for the decomposition of the precursor. The structure, microstructure, sur face roughness and optical properties (i.e, refraction index) have been det ermined for the two sets of samples. The 'as prepared' samples were very co mpact and dense and had a very low surface roughness. The (O-2(+))-ZrO2 sam ples were transparent and had a high index of refraction (n = 2.20 at lambd a = 660 nm). On the contrary, the (O-2(+)-Ar+)-ZrO2 films showed a greyish aspect after preparation, probably because of the existence of lattice defe cts in their structure. These defects were removed by annealing in air at T T 573 It. Then, the films became transparent and had a slightly lower refra ction index than that of the O-2(+)-ZrO2 films subjected to the same therma l treatments. For the (O-2(+)-Ar+)-ZrO2 thin films, it was shown by X-ray p hotoelectron spectroscopy (XPS) and Rutherford back scattering (RBS) that A r (4 at.%) remained incorporated within the oxide lattice even after anneal ing at T = 773 K. The incorporation of Ar atoms within the ZrO2 network ind uced significant modifications in the crystallographic structure of the fil ms. Thus, while X-ray diffraction (XRD) and Fourier transform infrared spec troscopy (FT-IR) showed that the (O-2(+))-ZrO2 films consist of a mixture o f of monoclinic and tetragonal phases of zirconia, the (O-2(+)-Ar+)-ZrO2 fi lms depicted, at 298 K, a high degree of amorphisation. However, these film s yielded a cubic/tetragonal phase after annealing at T > 573 K. The role o f the embedded Ar in inducing these structural changes is discussed. (C) 20 01 Elsevier Science B.V. All rights reserved.