Nanoscratch behaviors of La0.7Sr0.3MnO3+δ thin films

The nanoscratch behaviors of La0.7Sr0.3MnO3+δ films, which were deposited with ratio of O2/(O2+Ar), ranging from 4.4% to 45.6%, by DC magnetron sputter, were investigated by a nanoindentation technique. The results indicated that the friction coefficient between the films and the diamond tip depended on the loading critical load. The friction coefficient was about 0.08–0.12 when the loading normal load was less than the loading critical load. The films displayed excellent elastic recovery after unloading. When the loading load was larger than the loading critical load, plastic deformation and ploughing appeared for the films. The friction coefficient was about 0.43 when the film was damaged completely. The suitable decrease in ratio of O2/(O2+Ar) could improve the nanoscratch resistance of the films. The film deposited with O2/(O2+Ar)=25% possessed better scratch resistance due to good elastic recovery, high nanohardness, and critical load. The loading critical load of the film was larger than 80 mN.