Evidence of omega-phase in ion beam sputtered zirconium thin films

Zirconium thin films were sputtered at room temperature with Ar+ ion beam ( 1200 eV, 80 mA) on different substrates (Si, oxidized Si, amorphous quartz, ...). Although classical 2 atom hcp a-phase was expected at normal pressure conditions, present paper proves the occurrence of the high pressure phase of zirconium: three atom hexagonal omega-phase. TEM diffraction patterns a nd grazing incidence X-ray diffraction spectra clearly show the existence o f a phase different from the a-one. The unexpected phase was identified as the omega-one by means of CEEXAFS experiments. Moreover, results show that significant fraction of omega-phase coexists with alpha-grains which presen t a considerable increase of the interplanar distances. Substrate curvature induced by the deposit reveals an important compressive stress in the film . This residual stress is explained by conditions of non equilibrium mainta ined during the growth by the continuous ion bombardment of the subsurface region. Annealings performed at 700 degrees C show that the omega-phase rel axes in the alpha-phase. (C) 1999 Elsevier Science S.A. All rights reserved .