Effects of applied voltage on the properties of anodic zirconia thin film on (100) silicon

The formation of thin zirconium dioxide (ZrO2) film by anodisation of 150 nm thick zirconium (Zr) film on n-type silicon (Si) was investigated. Anodisation was performed in 1 M NaOH (pH 14) at six different voltages ranging from 5 V to 60 V. All anodisation processes were done for 15 min at room temperature in the bath with constant stirring. At lower voltages (5 V and 10 V), the anodised films are crystalline with high temperature cubic or tetragonal ZrO2 phases. For films anodised at voltages >20 V, monoclinic ZrO2 appears along with the tetragonal or cubic ZrO2. The monoclinic phases exist mostly at the top part of the oxide with more tetragonal or cubic ZrO2 nearer to the oxide/substrate interface. For samples anodised above 40 V, the oxide cracks severely and delaminates from the substrate with the degree of delamination more severe as the anodisation voltages were increased to 60 V. At these voltages, the high temperature phases are no longer stabilised leading to the phase transformation to monoclinic ZrO2. Anodisation at 20 V is therefore thought as an adequate voltage for the formation of relatively smooth oxide. This oxide has a root-mean-square value of 0.55 nm, no cracks and reveals the highest breakdown voltage. (C) 2012 Elsevier B. V. All rights reserved.