Nanocrystalline titanium films deposited via thermal-emission-enhanced magnetron sputtering

Abstract

Nanocrystalline titanium films were deposited at ultra-high current density by a direct-current closed-field unbalanced magnetron sputtering technique. The structures and properties of the films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and nanoindentation microscratch. The Ti film deposited at target current density of 0.267A/cm2 exhibited a polycrystalline microstructure with average grain size of 16nm, fine columnar structure with no obvious voids and smooth surface, better film thickness uniformity in different parts, and excellent film–substrate adhesion. These results showed that the excellent film structure and performances were primarily achieved by using high ionization rate and energy of target atoms. As current density exceeded 0.175A/cm2, ionization rate and energy of target atoms were greatly improved owing to the thermally-enhanced spontaneous emission of atoms and electrons from the target by Ar+ bombardment and Joule heating.