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RELAXATION-CRYSTALLIZATION PROCESSES IN Al-TE BINARY AMORPHOUS THIN FILMS
Marko Jerčinović1, Tihomir Car1, Nikola Radić1 1Ruđer Bošković Institute, Bijenička cesta 54, Zagreb, Croatia Jovica Ivkov2 2Institute for Physics, Bijenička cesta 46, Zagreb, Croatia
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Introduction & motivation
Amorphous alloys of early transition – late transition (TE-TL) metals are interesting because of their good mechanical and corosion properties Al-TE alloys are amorphous in a wide range of compositions For the application of these alloys at elevated temperatures it is important to investigate their thermal stability by study of relaxation and crystallization kinetics
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Sample preparation Kurt J. Lesker CMS-18 Magnetron Sputtering System
Preparation conditions: Residual pressure: 2.6 x 10-6 Pa Working gas (Ar) Pressure: 0.66 Pa Temperature: ~ 293 K Substrate: alumina ceramics 4 magnetrons magnetron shutters
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Electrical measurements
The isochronal resistivity measurements were performed by the four-probe method and by standard ac technique with the computer controlled data acquisition. The samples were radiatively heated in a vacuum chamber at a pressure of about 10-3 Pa. The exact thickness of the films investigated is of no importance, since all the results obtained were normalized to the electrical resistance at the room temperature. Assuming the linear dependence of resistivity with temperature (R/RRT ~ α·ΔT) in the observed temperature interval (RT – 400°C), the relaxation effects were extracted from the R(T) dependence.
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Relative resistivity vs. temperature (w/o linear dependence)
Al-Mo alloy – different compositions
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Relative resistivity vs. temperature (w/o linear dependence)
Al-TE alloy – different TE metal
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Fitting function a, b, c – parameters Bloch-Grüneisen formula [1]
TS – temperature shift qD – Debye temperature n = 2 Law of modified addition [2]: r – density [1] D. Cvijović, Theoretical and Mathematical Physics 166(1), 37–42 (2011) [2] S. Stoimenov et al, Journal of Materials Science: Materials in Electronics 14, 777–778 (2003)
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Al-Mo alloy – different compositions
Fitted curves Al-Mo alloy – different compositions Al80Mo20 Al75Mo25 Al70Mo30 (T-Ts) / qD
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Al-TE alloy – different TE metal
Fitted curves Al-TE alloy – different TE metal Al75W25 Al75Ta25 Al75Mo25 (T-Ts) / qD
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Fitted parameters alloy θD (K) Ts (K) a b c Al80Mo20 439.0 400 0.661
-0.461 Al75Mo25 437.5 384 1.000 -0.781 Al70Mo30 436.1 396 0.724 -0.658 Al75W25 419.3 340 0.351 -0.086 -5·10-4 Al75Ta25 340.5 0.127 -0.036 -8·10-4
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Conclusion Assuming linear temperature dependence of resistivity, relaxation effects were extracted and fitted to a modified Bloch-Grüneisen formula The fit is reasonably good in the measured temperature range (RT – 400°C), for various compositions and alloying TE metals It remains to find out the physical meaning of the fitted parameters and to extend the research to other amorphous alloys of various compositions ~ x5 ~ x3 ~ x2 ~ x BGF2(x) BGF3(x) BGF5(x)
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