Study on preparation and characteristics of Fe- and Mn-doped AlN thin films

Fe- and Mn-doped AlN thin films were prepared on Si substrates by direct current (DC) magnetron co-sputtering method in the atmospher of Ar and N2 mixture. The influences of sputtering currents and the target to substrate distance on the structure of the films were investigated by X-ray diffraction and Raman spectroscopy, respectively. Surface morphology and composition were studied by scanning electron microscope (SEM) with an energy dispersive X-ray spectroscopy (EDS) attachment. The magnetism of Mn- and Fe-doped AlN films was measured by vibrating sample magnetometer (VSM) at room temperature (RT). Processing of the Mn-doped AlN films produces Mn clusters in the samples. Due to the presence of the antiferromagnetism Mn clusters, ferromagnetism is either suppressed or disappears. The Fe-doped AlN films show ferromagnetism at RT, which should arise from the AlFeN ternary alloy. With the increase of the Fe target sputtering current, the Fe concentration is increased from 6.81 at.% to 16.17at.%; the saturation magnetization Ms is reduced from 0.27 emu·cm-3 to 0.20 emu·cm-3, and the coercive force Hc is increased from 57 Oe to 115 Oe, this is because the separation of Fe ions get shorter and the antiferromagnetic coupling is enhanced.