engleski

Investigation of thermal stability of Al-Mo films

The thin AlxMo100-x films (90 ≤ x ≤ 30 with x in steps of 5 at% Al) were prepared by magnetron codeposition at room temperature. The films were prepared on alumina, glass and saphire substrate. The film thickness was about 400 nm. The as-deposited films were amorphous for 45 ≤ x ≤ 85, as revealed with the grazing incidence X-ray diffraction (GIXRD) method. The films were first investigated by measuring the changes of the electrical resistivity with temperature, ρ(T), during the isochronal heating. The dynamical temperatures of crystallization, Tx, were determined from the sharp increase of the derivative of ρ with respect to temperature. No systematic dependence of Tx on film substrate has been observed. The temperature of crystallization has a maximum around 530oC for x = 55 and 60, what is not very large for amorphous transition metal based alloys. Electrical resistivity of both amorphous and crystallized films shows a strong dependence of electrical resistivity on alloy composition with a maximum for Al75Mo25. The resistivity of Al75Mo25 is 1000 μΩcm and 3000 μΩcm in amorphous and crystallized film respectively with the large negative temperature coefficient of resistivity of -10×10-4 K -1 and 14×10-4 K -1 respectively. The evolution of the crystalline structure in AlxMo100-x films during heating was determined by measuring GIXRD after annealing each film at preselected temperatures. For 80≤x≤90 we found Al12Mo (x=90), Al5Mo (x=85) and Al4Mo (x=80) Al-rich intermetallic compounds, while for 40≤ x≤75 a coexistence of Al8Mo3 and AlMo3 phases was found with the fraction of AlMo3 phase increases as x decreases.

nanostructured materials; Al-Mo thin films; thermal stability

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