Phase transformations in films deposited by laser ablation of Hf in an oxygen atmosphere

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 HfO2. 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.