Structural, microstructural and morphological properties of Permalloy/Si (100) thin films

We synthesized Permalloy Ni80Fe20 (Py) thin films on Si (100) substrates, using physical vapor deposition technique under vacuum. We investigate the effect of the thickness of the magnetic layer, ranging from 174 to 307 nm, on the physical properties of these films. We used the X-ray diffraction technique to analyze the structure, the scanning electron microscope to investigate the microstructure and the atomic force microscope to observe the surface morphology and carry out the film roughness. All the films have been found to crystallize in the face centered cubic structure with <111> preferred orientation. The increase of thickness provoked an increase of both the crystallite size and the lattice parameter. The crystallite size ranged from 14.620 to 19.710 nm. The thinnest film exhibited a lattice parameter equal to 3.5137 & Aring;, smaller than the bulk one, whereas the thickest film had a lattice parameter equal to 3.5580 & Aring;, greater than the bulk cell parameter. The micro-stress was confined between -1.09% for the thinnest film and +0.16% for the thickest one. The thinnest film was found to have a very smooth topographic surface, not exceeding 0.2 nm, the roughest film being the thickest one, with a root mean square roughness of 2.5 nm and exhibiting few microcracks.