OPTIMIZATION OF SPUTTERED CO FILMS

Co films in the thickness range of 120-230 nm have been sputtered on quartz glass and monocrystalline sapphire (1120BAR) substrates. A preferential orientation of the hcp [0001]- and the fcc [111]-axis, respectively, has been observed at low sputtering rates (0.05 nm/s) and after optimization of the substrate temperature T(s). For 200-degrees-C less-than-or-equal-to T(s) less-than-or-equal-to 300-degrees-C the structural coherence length normal to the film-plane reaches its maximum. The measured lattice spacings d are between the bulk values d(0002) and d(111) of the hcp- and the fcc-phase, respectively, and reach a minimum in the same range of temperatures. REM investigations supplement the X-ray measurements. Furthermore, thinner Co films (10-25 nm) were sputtered at 250 and 300-degrees-C. X-ray patterns show superior film quality at 300-degrees-C, slightly dependent on Ar pressure.