Studies of the effects of addition of P and Cr on microstructure and electrical resistivity of nanocrystalline CoFe thin films

Abstract

In this study, CoFe, CoFeP and CoFeCr thin films were electrodeposited at different current densities and the relation between their microstructure and electrical resistivity were studied. In order to characterize deposited films, field emission scanning electron microscope (FE-SEM) equipped with energy dispersive X-ray spectrometer, X-ray diffraction system and four probe-point methods were utilized. The results showed that an increase in the applied current density results in increasing iron, phosphorus and chromium contents in the coatings. FE-SEM and SEM micrographs illustrated that addition of phosphorous and chromium to CoFe changes the surface morphologies. Increasing current density caused formation of BCC (Fe) phase structure along with FCC (Co) phase in CoFe coatings. However, all CoFeP and CoFeCr thin films were consisted of only BCC (Fe). Estimation of crystallite size of the deposited films by Scherrer formula showed that all coatings had nanocrystalline structures and decreasing of crystallite size led to significant increase in electrical resistivity of the films, which was according to “scattering hypothesis”. CoFeP thin films showed higher electrical resistivity than those of CoFe and CoFeCr films.