Synchrotron analysis of structure transformations in V and V/Ag thin films

Crystal structure transformations in V(25 nm)/SiO2(001) and V(25 nm)/Ag(25 nm)/SiO2(001) thin films during annealing in vacuum of 10−3 Pa in the temperature range from 400 °C to 600 °C have been investigated by synchrotron X-ray powder diffraction. Crystal lattice parameters of VOx phase were evaluated for all transformations stages as well as its tetragonality degree. Additional techniques such as in-situ electron diffraction, secondary ion mass-spectrometry and transmission electron microscopy have been applied as well. Introduction of the Ag layer affects the V film structure and its oxidation property during annealing. The body-centered monoclinic (bcm) lattice forms in V films after annealing. On the other hand, presence of the Ag layer leads to formation of the body-centered tetragonal (bct) structure during annealing at the same temperature. Ag suppresses oxygen incorporation into the film during annealing due to its diffusion into V grain boundaries and following diffusion induced grain boundary migration, leading to decrease of vanadium grains size. Mentioned above structural changes have not been detected for samples annealed in a vacuum of 10−7 Pa in the same temperature range.