Nanocomposites and nanomaterials

Size effect in electrophysical properties of thin films based on permalloy and silver
D.O. Shuliarenko, I.M. Pazukha
Sumy State University, 2 R.-Korsakov St., Sumy-40007, Ukraine
e-mail: denissuliarenko@gmail.com
The modern stage of the electronic development, which is characterized by the exhaustion of the potential of traditional semiconductor technologies, demonstrates an active search for innovative approaches for the creation of functional elements of electronic devices. This fact stimulates the transition to a nanosize level of electronic devices production and investigations of thin film systems with a thickness less of than 100 nm. At the same time, the behavior of thin films electrophysical properties (the resistivity and the temperature coefficient of resistance (TCR)) is determined by size effect. Therefore, the mean purpose of our work is an investigation of the size effect in electrophysical properties of such nanosized structures based on ferromagnetic alloy Ni80Fe20 (permalloy) and silver prepared by the co-evaporation method. 
Thin film samples were prepared by electron-beam co-evaporation using permalloy Ni80Fe20 and Ag independent sources at room temperature in the HV chamber with a base pressure 10-4 Pa. The condensation rate was 0,1 nm/s. The series of samples with a thickness that changed in the range from 20 to 60 nm were obtained. The thickness of the samples was controlled by the method of «in situ» quarts resonator. The composition of the samples was controlled by scanning electron microscope equipment with an energy dispersive detector to perform the X-ray spectrometry Tescan VEGA3. The concentration of Ag atoms in all samples was 60 at. %. The heat treatment of the samples in the temperature range 300-700 K was conducted in a vacuum chamber in the automatic regime. The temperature dependences of resistivity ρ(Т) was created based on experimental data. The value of TCR was calculated according to the equation β = (1/ρin(Δρ/ΔТ), where ρin is the initial value of resistivity, ΔТ = 5 К.
Analysis of experimental dependences ρ(T) and β(T) for nanodimesional thin film samples based on permalloy and silver showed that: (i) the character of temperature dependences of resistivity and TCR is typical for the components of the system, wherein ρ have an order of 10 – 7 Оhm·m, and β – 10 – 3 К – 1; (ii) the grows of the total thickness of the samples leads to the decrease in the resistivity value in 5 times; (iii) the TCR value increases in 2 times at the thickness grows.
This work was funded by the State Program of the Ministry of Education and Science of Ukraine 0119U100777.