Substrate Bias Voltage Effect on Amorphous TbCo Sputtered Films

The effect of substrate bias voltages (VB = 0 to -300 V) on TbCo amorphous films formed by RF sputtering, at an Ar pressure of 20 mTorr and an input power of 100 W, was studied. For large bias voltages, both Ms and Ku increased with VB, the latter peaking at around -150 to -200 V. EPMA compositional analysis indicated that the Tb content decreased relative to Co as VB was increased; this was attributed to selective re-sputtering of Tb. The Ar and oxygen contents also depended on VB. Studies of the film microstructure suggested a relation between structure and perpendicular anisotropy.