Low energy ion beam assisted deposition of biaxially aligned yttria stabilized zirconia films on polycrystalline Ni–Cr alloy

Abstract

(0 0 1)-oriented and in-plane aligned yttria stabilized zirconia (YSZ) thin films have been synthesized on polycrystalline Ni–Cr alloy substrates by low energy ion beam assisted deposition (IBAD). The biaxial alignment of YSZ films on polycrystalline substrates was found to be mainly controlled by the incident angle and energy of the bombarding Ar + ions. Under incident angle of 55° and ion energy of 250–500 eV, optimal biaxial alignment of the film was obtained. The biaxial alignment of the YSZ needs about 1000 Å thickness to develop. Monte Carlo method has been used to simulate the formation of YSZ biaxial alignment with Ar + bombarding zirconia crystals oriented with 〈0 0 1〉 parallel to normal of the film. Results of the simulation indicate that when the energy of the bombarding ions is below 50 eV, there is no obvious difference in the sputtering yields and the radiation damage of zirconia between different incident angles. However with the ion energy increasing, the variation increases rapidly. When the ion energy reaches 250 eV, the sputtering yields and the radiation damage of the (0 0 1)-oriented zirconia induced by Ar + bombardment along [1 1 1] direction (54.7° from [0 0 1]) of the zirconia are minimum as compared with those induced by Ar + bombardment along other directions. It could be concluded that YSZ grains with [0 0 1] orientation normal to the substrate are far less sputtered than other oriented grains under ion beam bombardment at 55° incident angle, which causes (0 0 1)-oriented YSZ grains to prevail over initial random oriented grains. So that the biaxial alignment is formed.