Formation of Co, Fe, and Co-Fe nanoparticles through solid-state dewetting in the presence of hydrogen plasma and their electrical properties

This paper investigates the surface and electrical characteristics of cobalt, iron, and cobalt-iron nanoparticles, based on the variation of film thickness and plasma treatment time. These ferromagnetic nanoparticles were formed by dewetting the thin films in the presence of hydrogen plasma. The results indicated that particle size increases with increasing film thickness and plasma treatment time. Film thickness lower than 4 nm represents a highly dense distribution of small (<20 nm), partially spherical particles; which indicates the fast agglomeration kinetically driven by surface diffusion. When studying the influence of particle size and interparticle distance to the resistivity and magnetoresistance, an improved resistivity is achieved with increasing plasma treatment time from 10 min to 60 min. This result is due to the longer coalescence time required to form larger particles. A significant increase of magnetoresistance is observed in dense Co20Fe80 nanoparticle, which is at least 35% higher than that of the other materials. For all cases, the magnetoresistance tends to decrease with increasing film thickness and plasma treatment time. This behavior is caused by the interparticle distance between the interacting neighboring particles, and this interaction known as tunneling effect.