Morphological transformations of vanadium oxide films during low-temperature reduction in hydrogen electron cyclotron resonance plasma

Morphological transformations of amorphous vanadium oxide films obtained by the sol-gel method and polycrystalline V₂O₅ films are studied during their low-temperature (295–623 K) reduction in a hydrogen electron cyclotron resonance plasma. The morphology of films is analyzed using atomic force microscopy and high-resolution electron microscopy. It is found that a homogeneous amorphous film during the reduction process transforms to an island film and then bulk amorphous islands of a regular shape appear. These islands resemble microcrystals, and their concentration depends on the temperature and the reduction time. The low-temperature reduction of polycrystalline V₂O₅ films leads to their amorphization; however, the microcrystals in the polycrystalline film do not change their shape in this process. A mechanism of the reduction process is proposed. This mechanism explains the regularities of morphological transformations in amorphous sol-gel films of vanadium oxides based on the suggestion of a competition between the ion-stimulated nucleation and growth of nuclei of the crystalline phase and the amorphization of the growing nuclei.