The structure of the hafnium dioxide films grown during pulsed laser sputtering of an Hf target in an oxygen atmosphere is examined, and the phase transformations that occur in them at annealing are studied by transmission electron microscopy and electron diffraction. Amorphous, tetragonal, orthorhombic, and monoclinic HfO 2 phases are detected in the films. The tetragonal modification of HfO 2 exhibits an epitaxy effect on a KCl(001) substrate. When the amorphous film is annealed in vacuum or air, it crystallizes to form the monoclinic modification of HfO 2 . The action of an electron beam on the amorphous film in vacuum leads to the formation of the orthorhombic and monoclinic modifications of HfO 2 . The transformation from the orthorhombic to the monoclinic modification of HfO 2 is accompanied by a phase size effect. At the final stage of crystallization, the monoclinic modification represented by HfO 2 dendrite crystals is the predominant structural constituent.Results of electron diffraction analysis of the films deposited by pulsed laser sputtering of an Hf target in an oxygen atmosphere Line no. Deposition at T s = 410 K Deposition at T s = 290 K followed by air annealing at 770 K d, nm hkl d, nm t. phase JCPDS Card 08 0342 d, nm t. phase JCPDS Card 43 101 d, nm hkl d, nm t. phase JCPDS Card 43 101

The flow velocity of solid 4 He through a porous membrane frozen into a crystal has been measured in the temperature interval 0.1 -1.8 K. A flat capacitor consisting of a metalized plastic porous membrane and a bulk electrode is applied and the gap in the capacitor is filled with examined helium. The flow of helium through the membrane pores is caused by a d.c. voltage applied to the capacitor plates. Above T~1 K the velocity of solid 4 He flow decreases with lowering temperature following the Arrhenius law with the activation energy of the process closed to that of vacancies. At low temperatures the velocity is practically independent of temperature, which suggests a transition in 4 He from the classical thermally activated vacancyrelated flow to the quantum plastic flow.

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