Effect of ion bombardment on the surface morphology of Zn-films sputtered in an unbalanced magnetron

It is well known that magnetron sputtered films of low melting point Tm materials have (due to their crystallisation at low substrate temperatures, T < 100oC) rough and diffusely reflecting surfaces, even when thin, for instance about 20 nm for In films. Only extremely thin films have a smooth and specular reflecting surface. This paper reports on the possibility of sputtering thick films of low Tm materials with a smooth, optically specular reflecting surface using an unbalanced magnetron. To demonstrate this possibility, Zn films were studied and it was shown that a surface roughness of the film can be effectively controlled by ion bombardment of the film during growth. The smoothing of the Zn film does not depend on film thickness but on ion bombardment of the growing film. (author)