Effects of incidence angles on the microstructure of Co–Nb thin films prepared by ion beam assisted deposition

Ion incidence angle plays an important role during the ion beam assisted deposition process. In this study, incidence angle effects on the microstructure, morphology and thermal stability of Co30Nb70 thin films deposited by ion beam assisted deposition have been investigated. The films were deposited at a fixed ion energy of 4 keV and ion current density of 12 μA/cm2. The experimental results show that Co30Nb70 amorphous alloy is formed, when incidence angles are from 0° to 75°. To investigate stability versus incidence angle, all the samples were annealed at 300 °C and 450 °C, respectively. It was found that most of the Co30Nb70 films remained amorphous after being annealed at 300 °C for 30 min, while a bcc metastable phase appeared in the film deposited with incidence angle of 45°. After being annealed at 450 °C for 30 min, the new bcc phase dissolved into amorphous phase again and some films became partially crystallized. The possible mechanism of microstructure evolution is discussed in terms of the mixing, thermal spike, internal stress, and the variations of the process of film growth induced by incidence angles.