Petrushenko S. Phase transitions and temperature evolution of the morphological structure of multilayer films consisting of layers of fusible metals (Pb, Bi, Sn or In) and more refractory substances (C, Mo or Cu)

Thesis for a Doctor of philosophy degree (Ph.D.) in physics and mathematics on speciality 01.04.07 – Solid State Physics. V.N. Karazin Kharkiv National University, Kharkiv, 2018. The thesis is devoted to the determination of supercooling during the crystallization of layers of the liquid phase of low-melting metals (Pb, Bi, Sn, In) located between layers of more refractory substances (C, Mo, Cu), to the study of the thermal stability of single and multilayer films, and to the solubility in vacuum condensates. The values of supercooling in layered film systems are determined and it is found that in the films Cu/Bi and Mo/Bi the temperature and character of the crystallization of bismuth (diffuse or avalanche) is determined by the mechanism of its condensation. For samples in which bismuth was condensed by the mechanism of vapor-crystal, an avalanche-like crystallization is characteristic. It occurs with relatively small supercoolings. The crystallization of bismuth in samples in which it was deposited by the vapor-liquid mechanism has a diffuse form and occurs at lower temperatures In the course of the study of the features of the de-wetting of film systems, the activation energies of the decay of fusible metal films (Pb, Sn, In) on a carbon substrate were determined. It should be identified with the activation energy of self-diffusion in the samples. It is established that the germs of through-pores, the growth of which actually provides de-wetting of the samples, are formed in the films even during the condensation stage. The preliminary annealing of copper films, which is carried out at temperatures substantially lower than those that ensure the decomposition of the films into separate islands, increases the thermal stability of the samples, but the addition of lead (in an amount of more than 3% by weight), ensures the dispersion of Cu/Pb films at a temperature melting of lead. The activation energy of the de-wetting in Pb/Cu films is only 0.2 eV, while for copper films the analogous value is 1.6 eV. By in situ electrocornographic studies in Pb/Cu and Bi/Cu films, copper solubility in the low-melting component was determined. The values obtained exceed the values known for bulk samples.