Study of structural relaxation processes of nonequilibrium states in quench‐condensed indium films with hydrogen impurities below 5 K

Abstract

The structural state of quench-condensed polycrystalline indium films with hydrogen impurities is studied by the electron diffraction method. The films (3 to 14 nm thick) are deposited with rates of 0.3 to 2 nmjs in hydrogen atmosphere (pH M 1.6 x Pa) onto substrates cooled by liquid helium to 2.5 K. The films exhibit high nonequilibrium hydrogen concentration (up to z 15 at%) and their state is labile. During the transition to a more stable state (at constant temperatures or with heating in the range 2.5 K s T s 5 K) hydrogen in films is highly mobile. The attendant structural relaxation consists in alternating increase and decrease of the lattice parameters in microcrystallites. Simultaneously crystallites undergo inhomogeneous strains. The behaviour of the relaxation process shows some symptoms of spinodal decomposition. There are, however, essential distinctions from the features of spinodal decomposition, which are known for bulk metal-hydrogen systems. Results obtained are discussed taking into account the influence of the two-dimensionality of the films and their inhomogeneous (granular) structure on nonequilibrium state decomposition.Der Strukturzustand abgeschreckt-kondensierter feinkristalliner Indium-Schichten mit Wasserstoffzusatz wird mit Hilfe von in situ Elektronenbeugung untersucht. Die Schichten (3 bis 14 nm dick) werden bei Aufdampfraten von 0,3 bis 2 nm/s in Wasserstoffatmosphiire (pH = 1,6 x lo-* Pa) auf einen