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S. I. Ryabtsev, О. V. Sukhova
«Structure and Electrical Properties of Thin Al\(_{66}\)Cu\(_{18}\)Co\(_{16}\) and Al\(_{69}\)Co\(_{16}\)Ni\(_{15}\) Films»
729–736 (2019)

PACS numbers: 61.43.Dq, 61.44.Br, 64.60.My, 73.61.At, 81.07.Bc, 81.15.Cd, 81.15.Rs

For the first time, thin films with the Al\(_{66}\)Cu\(_{18}\)Co\(_{16}\) or Al\(_{69}\)Co\(_{16}\)Ni\(_{15}\) nominal compositions and of 85–100 nm thickness cooled at \(10^{12}–10^{14}\) K/s are produced by method of modernized three-electrode ion-plasma sputtering of composed targets. Thin films are deposited on sodium chloride or glass-ceramic substrates. The coatings are analysed with x-ray diffraction (XRD). Electrical resistivity is measured by four-probe method. An amorphous phase and traces of quasi-crystalline decagonal D-phase are observed in the structure of the deposited films. Coherent scattering regions (CSR) of as-sputtered Al\(_{66}\)Cu\(_{18}\)Co\(_{16}\) and Al\(_{69}\)Co\(_{16}\)Ni\(_{15}\) thin films are found to be 2.8 nm and 3.2 nm, respectively, in size. Over a temperature range from 293 K to 600 K or 640 K for these Al\(_{66}\)Cu\(_{18}\)Co\(_{16}\) or Al\(_{69}\)Co\(_{16}\)Ni\(_{15}\) films, the reversible change in an electrical resistivity of the deposits is observed that indicates absence of phase transformations. As the temperature is raised up to 920 K, irreversible decrease in electrical-resistivity evidences that the structure of films starts changing. An amorphous phase disappears, and aluminium-based metallic phase appears in the films’ structure. After annealing for 10 minutes at 923 K, the films exhibit coarser structure. Post-annealing treatment reveals that CSR of quasi-crystalline icosahedral phase become of 6.0–6.5 nm in size, so a twofold increase in their dimension is observed as compared to that of the as-sputtered films. The films consist of isolated quasi-crystalline nanoparticles embedded in the aluminium matrix at the given compositions and deposition conditions. Under both heating and cooling, temperature coefficients of resistance (TCR) are of negative values that relates to quasi-crystalline structure of films. With temperature decreasing from 920 K to room temperature, TCR of the Al\(_{66}\)Cu\(_{18}\)Co\(_{16}\) film increases from \(\approx\) -4\(\cdot\)10\(^{-4}\)K\(^{-1}\) to -1.2\(\cdot\)10\(^{-5}\)K\(^{-1}\), and that of the Al\(_{69}\)Co\(_{16}\)Ni\(_{15}\) film—from \(\approx\) -5\(\cdot\)10\(^{-4}\)K\(^{-1}\) to -2.4\(\cdot\)10\(^{-4}\)K\(^{-1}\). Therefore, the Al\(_{66}\)Cu\(_{18}\)Co\(_{16}\) film shows promise as the material for fabrication of thin-film precise low-ohmic resistors.

Keywords: ion-plasma sputtering, thin films, quasi-crystalline decagonal phase, electrical resistivity, temperature coefficient of resistance

https://doi.org/10.15407/nnn.17.04.729