Grain size effects in metallic thin films prepared using a new sputtering technology

In this paper we show how the grain size of metallic sputtered films can be controlled using a novel sputtering technology (HiTUS). This is evidenced by TEM and grain size analysis, which show changes of up to a factor 10in the mean grain diameter of CoFe thin films. We achieved the grain size control by tuning the target bias voltage, which had the effect of changing the energy of the Ar ions. This is due to the unique design of the HiTUS sputtering plant in which the plasma generation is decoupled from the sputtering chamber and the bias voltage is not required to sustain a plasma glow discharge. Grain size control has been applied to a series of polycrystalline 20 nm thick CoFe films and a series of applications arising form the ability to control the grain size are presented. In particular, we show that the coercivity, resistivity and exchange bias field have a strong dependence on the mean grain size.