Formation of {111} oriented domains during the sputtering epitaxy growth of (001) oriented Iridium films

In the wafer-scale growth of Ir(001) on yttria-stabilized zirconia (YSZ) by magnetron sputtering epitaxy two kinds of {111} oriented domains are observed. One consists of sharp 'fjord'-shaped features in which four 90 degrees alternated rotational variants of {111} are possible and the second one consists of islands with less defined shapes in which eight 45 degrees alternated rotational variants can be found. Their formation occurs directly at the Ir/YSZ interface along incoherent grain boundaries, likely nucleating at local defects of the YSZ surface. In order to avoid these misoriented domains, process separation and proper etching pretreatment of the wafers both before and between the sputtering processes have been found to be the key strategy for achieving reproducibility and overall better material quality.