Bogatyrenko S. Melting – crystallization and diffusion activity in Al/M/Al and Ge/M/Ge (M = In, Sn, Bi, Pb) layered film systems

Al/M, Ge/M (M = In, Sn, Pb, Bi) films with thickness of 100 nm each. Al/M/Al і Ge/M/Ge layered film systems with different thickness of M component (10–100 nm) and thickness of Al or Ge film about 100nm. Au-Cu 100 layer film system with each component thickness of 2 nm. Aim: establish the rules of the size dependence of the melting-crystallization phase transition and diffusion activity in Al/M/Al and Ge/M/Ge (M = In, Sn, Pb, Bi) layered film systems with component that form the phase diagram of simple eutectic type with complete insolubility of components in solid state. The methods of the investigations: Differential method of melting temperature measurements in layered film systems, electron microscopy, Auger-spectroscopy, diffraction techniques. Results, novelty: The decrease of the melting point of easy-melted component film (In, Sn, Bi, Pb) between thick Al or Ge film with the decrease of its thickness has been shown. The observed lowering of the melting temperature in our layered film systems has been described on the basis of a thermodynamic approach. This description takes into account the in-creased role of the interface energy under crystal-melt phase transition and evolution of the binary phase diagram of fusibility with film thickness decreasing. The efficiency of layered film system employment for determination of ultimate supercooling upon crystallization values has been shown by the example of Al/Bi/Al film system. The stability of the obtained values of supercooling during crystallization under multiple heating-cooling cycles has also been demonstrated. It is shown that in Au-Cu nanosize film system obtained via consequent condensation (regardless of layers condensation sequence) the formation of an alloy occurs even at room temperature. This takes place with the particles of such small size when the main fraction of the film material is associated with surface and near-surface atoms. This result indicates the dominant role of diffusion activity in studied system. Field of implementation:solid sate physics.