Influence of sputtering atmosphere on hopping conductance in granular nanocomposite (FeCoZr)x(Al2O3)1−x films

Abstract The present paper investigates conductivity σ for a wide temperature range of 2 K  T  x (Al 2 O 3 ) 1− x films (1–6 μm thicknesses, 0.30  x  2 gas mixture (set 2 films). TEM and HRTEM images revealed that granular films of set 1 containing nanosized crystalline metallic bcc α -FeCo-based nanoparticles embedded in the amorphous Al 2 O 3 matrix. In case of Ar + O atmosphere of deposited α -FeCo-based crystalline “cores” with stabilized sizes were covered with an amorphous FeCo-based oxide “shells”. The σ ( T ) dependences were found to be in agreement with this phase structure. They show transition of the set 1 films σ ( T ) curves with x from tunneling (hopping) behavior below the percolation threshold x x C  ≈ 0.46 to metallic one for x  >  x C . Moreover, as opposed to such behavior, for the set 2 films hopping mechanism of σ ( T ) was revealed far beyond x C due to the formation of semiconducting FeCo-based oxide “shells” separating electrically contacting FeCoZr cores.

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