Preparation and characterization of nanoporous columnar ZrO2 films by reactive magnetron sputtering

Nanoporous columnar ZrO2 films were deposited by reactive magnetron sputtering using glancing angle deposition (GLAD) configuration. The influences of deposition angle and target-substrate distance on the optical and structural properties of ZrO2 films were investigated. It is found that the ZrO2 films fabricated using GLAD show a tilted columnar microstructure; the width of the gap between two adjacent columnar crystals is less than 100 nm; the average grain size of ZrO2 films is about 10 nm; and the orientation of some grains can be changed by changing the deposition angle. In addition, with the increase in the deposition angle or/and target-substrate distance, the porosity of ZrO2 film increases while the refractive index and the deposition rate of ZrO2 film decreases. A larger deposition angle tends to increase the column inclination angle while a longer target-substrate distance tends to decrease the column inclination angle. The refractive index and porosity of ZrO2 films deposited at deposition angle of 75° are 156 and 417%, respectively.