Nanocrystalline zirconium oxide thin films grown under low pulsed dc voltages

Zirconium oxide thin films were deposited at room temperature by an off-plane filtered cathodic vacuum arc under a pulsed substrate bias between 0 and -250 V. The film properties including structure, surface morphology, mechanical and optical properties on n-Si(1 0 0) and quartz were investigated in terms of substrate bias. The results show that a strong effect of substrate bias on the film properties on n-Si(1 0 0) has been observed. With increasing substrate bias, the film changes from an amorphous state at floating bias to a randomly oriented crystalline structure at -100 V, and then to a preferred orientation along the [2 0 0] direction at -250 V. The stoichiometric ratio is decreased with increasing substrate bias as well as deposition rate. The film surface remains smooth at floating bias while large roughness is found when biases were applied. Besides, it is also observed that both hardness and Young's modulus increase with the substrate bias. However, for the films on quartz substrate, nanocrystalline film was found only at -250 V. Optical properties including optical constants and optical band gap (E_g) were investigated. The mechanisms of changes in structure and related properties were discussed.