Williamson–Hall method applied to VO2 thin films

Three samples of vanadium dioxide thin films with different crystallographic structures at room temperature, P2 1 /c (M1), P 1 ̄ (T), and a mixture of both (M1-T), were analyzed. Atomic force microscopy images obtained at room temperature show clearly that the thin films are composed of percolated nanocrystals. X-ray diffraction experiments using 7 keV synchrotron radiation were performed before and after the crystallographic transition to the rutile (R) phase, and the Williamson-Hall method was used to separate contributions from strain and from crystallite size. The presence of the strain in the R phase induces transition to the T phase as the temperature decreases through the transition. Williamson-Hall plots can also be used to obtain relative strain values from polycrystalline samples.